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The zirconia oxygen analyzer is suited for measurements of ppm to % amounts of oxygen in a fuel or mixture of gases. The zirconia cell is an electrochemical galvanic mobile employing a higher temperature ceramic sensor containing stabilised zirconium oxide.

In an instrument the zirconia cell is mounted in a temperature managed furnace with the required electronics to process the sign from the detection mobile. Typically measurements are displayed right through a electronic exhibit as oxygen concentration more than the variety .01ppm to 100%.

The theory driving Systech’s zirconia oxygen analyzer

The zirconia mobile is a substantial temperature ceramic sensor. It is an electrochemical galvanic cell comprising of two electrically conducting, chemically inert, electrodes hooked up to either side of a solid electrolyte tube. This is proven schematically in Determine one under.

The tube is fully fuel restricted and manufactured of a ceramic (stabilised zirconium oxide) which, at the temperature of operation, conducts electrical power by indicates of oxygen ions. (Note: In sensors of this type, the temperature has to be earlier mentioned 450°C just before they turn out to be energetic as an electrolyte conductor). The likely big difference throughout the mobile is given by the Nernst equation.



Exactly where:

E is the possible distinction (volts)
R is the gasoline continual (eight.314 J mol-1 K-1)
T is the complete temperature (K)
F is the Faraday continual (96484 coulomb mol-1)
P1 & P2 are the partial pressures of the oxygen on possibly aspect of the zirconia tube

The Nernst equation can therefore be decreased to:



Therefore, if the oxygen partial stress at one of the electrodes is known and the temperature of the sensor is controlled, then oxygen measurement of the likely difference among the two electrodes permits the unfamiliar partial pressure to be calculated.

Note


The partial force of the fuel is equal to the molar focus of the element in a gas mixture occasions the total pressure of the fuel mixture.

PO2 = CO2 P2

exactly where:

PO2 = Oxygen partial strain
CO2 = Molar concentration of oxygen
P2 = Whole stress

Example

For atmospheric air:

CO2 = 20.9%
P2 = one environment

PO2 = (.209/one hundred) x 1

PO2 = .209 atmospheres

Principle of Procedure
The zirconia mobile employed by Systech Illinois is manufactured of zirconium oxide stabilised with yttrium oxide as the ceramic with porous platinum electrodes. This cell is demonstrated in Determine one.



Determine one: Enlarged cross sectional representation of the zirconia substrate

Molecular oxygen is ionised at the porous platinum electrodes.

PtO → Pt + ½ O2
½ O2 + 2e- → O2–

The platinum electrodes on every facet of the mobile provide a catalytic floor for the adjust in oxygen molecules, O2, to oxygen ions, and oxygen ions to oxygen molecules. Oxygen molecules on the large concentration reference fuel aspect of the mobile achieve electrons to turn into ions which enter the electrolyte. Concurrently, at the other electrode, oxygen ions shed electrons and are unveiled from the area of the electrode as oxygen molecules.

The oxygen content material of these gases, and as a result the oxygen partial pressures, is diverse. Therefore, the rate at which oxygen ions are created and enter the zirconium oxide electrolyte at every electrode differs. As the zirconium oxide permits mobility of oxygen ions, the amount of ions moving in each and every path throughout the electrolyte will depend on the price at which oxygen is ionised and enters the electrolyte at each electrode. The mechanism of this ion transfer is sophisticated, but it is acknowledged to involve vacancies in the zirconia oxide lattice by doping with yttrium oxide.

The consequence of migration of oxygen ions across the electrolyte is a internet stream of ions in 1 path relying on the partial pressures of oxygen at the two electrodes. For instance in the Nernst equation:



If P1>P2 ion movement will be from P1 to P2 i.e. a positive E.M.F.
If P1If P1=P2 there will be no net ion flow i.e. a zero E.M.F.

In the zirconia analyzer, the Nernst equation is written



The zirconia analyzer uses air as a reference, a constant oxygen concentration of 20.9%, and the zirconia cell is mounted inside a furnace whose temperature is controlled to 650°C (923 K).

Thus, our Nernst equation further reduces to:



The zirconia analyzer electronically calculates the oxygen partial pressure, and therefore oxygen concentration, of a sample gas with unknown oxygen concentration. This is accomplished by measuring the potential, E, produced across the zirconium cell electrodes, substituting for E in the Nernst equation and anti-logging to obtain PO2. The cell potential output is shown in Figure 2.



Vacuum gauge of cell potential vs. oxygen concentration of zirconia cell.

By anti-logging the equation, the output signal can be displayed directly on a digital readout meter as oxygen concentration in ppm or %.

Calibration
As the zirconia instrument uses an absolute measurement principle once built and factory calibrated, it does not require any further factory calibration.

Factory calibration consists of calibration of the electronics to accept the millivolt input signal from the detection cell and checking that the instrument then reads correctly on air, 20.9%. The instrument is then further checked for correct reading on ppm oxygen content in nitrogen.

Applications of zirconia oxygen analyzers

The zirconia analyzers may be used for measurement of oxygen at any level between 0-100% in gases or gas mixtures.

The only restriction on the instrument’s usage is that the gas to be measured must not contain combustible gases or any material that will poison the zirconium oxide detection cell.

Any combustible gas, e.g. CO, H2, hydrocarbons such as methane, in the sample gas entering the instrument will combine with any oxygen in the sample gas in the furnace due to the high temperature at which the furnace is kept. This will actually reduce the amount of oxygen in the sample gas and cause the instrument to give an incorrect low reading.

Materials that will poison the detection cell are:

Halogens e.g. Chlorine
Halogenated Hydrocarbons e.g. Methylchloride
Sulphur containing compounds e.g. Hydrogen Sulphide
Lead containing compounds e.g. Lead Sulphide
Gases or gas mixtures containing any of the above are not suitable for oxygen determination with a zirconia type oxygen analyzer.

The crucial element of a gas detector is a gas sensor. Fuel sensors can be divided into 3 classes in theory:

Gasoline sensors making use of actual physical and chemical properties: such as semiconductor type (surface control type, quantity management variety, surface area likely type), catalytic combustion sort, strong thermal conductivity type, and so on.
Gas sensors utilizing bodily properties: these kinds of as thermal conductivity, light-weight interference, infrared absorption, and so on.
Gasoline sensors making use of electrochemical qualities: such as continuous prospective electrolytic type, Galvanic battery variety, diaphragm ion electrode sort, mounted electrolyte kind, and so forth.
The basic principle of fuel sensors: In accordance to the hazards, we divide harmful and dangerous gases into two main classes, flammable gases and poisonous gases. Due to their various nature and hazards, their detection methods are also various.

Trace Oxygen analyzer is the most harmful fuel encountered in industrial apps these kinds of as petrochemical market. It is mainly organic gases this sort of as alkanes and specific inorganic gases:
This sort of as carbon monoxide, there have to be specified situations for a flammable gasoline to explode, that is: a specific concentration of flammable gasoline, a specific amount of oxygen, and ample warmth to ignite their ignition source. These are the three factors of the explosion (this kind of as the explosion triangle demonstrated in the left figure previously mentioned). No, that is, the absence of any of these problems will not result in hearth and explosion. When flamable gasoline (steam, dust) and oxygen are blended and attain a certain concentration, it will explode when it fulfills a hearth source with a specific temperature.

We refer to the concentration of a flammable fuel as it explodes when exposed to a fire source, referred to as the explosive concentration restrict, referred to as the explosive limit, and is usually expressed in%. In fact, this mixture does not explode at any mixing ratio but demands a concentration selection. The shaded spot is proven in the figure on the appropriate. Explosion does not take place when the focus of flammable gasoline is reduce than LEL (* reduced explosive restrict) (the concentration of flammable fuel is insufficient) and its concentration is larger than UEL (* higher explosive restrict) (minimal oxygen).


Distinct flammable gases have different LELs and UELs. This need to be taken into account when calibrating the instrument. For the sake of protection, generally we must concern an alarm when the flammable fuel concentration is 25% or significantly less and fifty% of the LEL. Listed here, twenty five% LEL is known as the minimal limit alarm and 50% LEL is called the higher limit alarm. This is why we phone the combustible fuel detector the LEL detector.

The theory of the fuel sensor: It ought to be famous that one hundred% shown on the LEL detector does not indicate that the focus of the flammable gasoline reaches a hundred% of the volume of the gas, but reaches one hundred% of the LEL, which is equal to the most affordable lower explosive limit of flammable gas In the scenario of methane, a hundred% LEL = 5% volume focus (VOL). Detection of flammable gases can be made making use of semiconductor, catalytic combustion (anti-toxic), thermally conductive and infrared sensors.

Harmful gas detection, at current, for the detection of specific toxic gases, we use the most dedicated gasoline sensors. There are 3 kinds of sensors for detecting poison gasoline: semiconductor kind, electrochemical sort and electrolytic mobile sort.
Semiconductor sensors this kind of as the continual likely electrolytic kind, Galvanic battery type, diaphragm ion electrode kind, and fixed electrolytic kind have substantial sensitivity and low resolution. Sensors of this basic principle have been nearly eliminated, and customers ought to be incredibly watchful when choosing these kinds of sensors. Electrolytic battery sensor sound electrolyte gasoline sensor utilizes solid electrolyte gas sensing material as the gas sensing component. The principle is that the gas-sensitive content generates ions when passing through the gasoline, thereby forming an electromotive force, and measuring the electromotive force to evaluate the gas concentration.

Thanks to its high conductivity, great sensitivity and selectivity, this sensor has been broadly utilised, and has virtually entered into numerous fields such as petrochemical, environmental protection, mining and other fields, next only to metal oxide semiconductor fuel sensors. This kind of as measuring YST-Au-WO3 of H2S, measuring NH + 4CaCO3 of NH3 and so on, Electrochemical sensors are presently extensively utilized sensors for detecting toxic gases. It uses redox reactions to detect dozens of toxic gases by means of various electrolytes.

The principle of the gasoline sensor: In accordance to the high quality of the electrolyte, its existence is normally two to four a long time. The composition of an electrochemical sensor is: two reaction electrodes, a operating electrode and a counter electrode, and a reference electrode are put in a particular electrolyte (as demonstrated in the determine earlier mentioned), and then a ample voltage is used between the response electrodes so that The redox response is done via the fuel to be calculated coated with a heavy metallic catalyst film, and then the recent produced during the gas electrolysis is calculated by the circuit method in the instrument, and then the microprocessor calculates the concentration of the fuel.

At current, electrochemical sensors are broadly used to detect inorganic toxic gases. Electrochemical sensors that can detect certain gases contain: carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrogen monoxide, nitrogen dioxide, ammonia, chlorine, and cyanogen Acids, ethylene oxide, hydrogen chloride, and many others.

Detection of Risky Natural and organic Compounds There is also a picture-ionization detector (PID) for the detection of unstable natural and organic compounds. It can evaluate natural harmful gases as low as ppm (and a single 10 thousandth) and Vapor focus
PID can detect most unstable natural and organic compounds (VOC). Basically place, PID can measure unstable natural and organic compounds with carbon numbers from 1 (for instance, CH2Cl2) to 10 (for example, naphthalene). PID can be utilised for the safety and overall health of a variety of kinds of organic compound firms that use, produce, retailer, and transport. At the very same time, it can also be utilized in numerous fields these kinds of as unexpected emergency mishaps in the environmental defense industry, industrial wellness consultation, general public stability inspection, and chemical prevention.

Oxygen detector Oxygen is also needed in industrial environments, especially in shut environments. Usually, we call the oxygen articles above 23.5% as excess oxygen (enriched oxygen), and it is straightforward to explode at this time even though the oxygen content material under 19.five% is oxygen deficiency (hypoxia), at this time employees are susceptible to suffocation and coma. To death. The regular oxygen content material need to be close to 20.9%. The oxygen detector is also a type of electrochemical sensor.

The crucial component of a fuel detector is a gasoline sensor. Gasoline sensors can be divided into three classes in principle:

Fuel sensors utilizing actual physical and chemical homes: this sort of as semiconductor type (surface area manage kind, quantity management type, surface area potential variety), catalytic combustion sort, strong thermal conductivity kind, and so on.
Fuel sensors using bodily properties: this sort of as thermal conductivity, mild interference, infrared absorption, and many others.
Gasoline sensors employing electrochemical homes: these kinds of as continuous possible electrolytic kind, Galvanic battery type, diaphragm ion electrode sort, mounted electrolyte variety, and so on.
The principle of gas sensors: According to the hazards, we divide harmful and harmful gases into two major groups, flammable gases and poisonous gases. Due to their different nature and dangers, their detection techniques are also various.

Flamable gasoline Flamable gasoline is the most unsafe fuel encountered in industrial apps this sort of as petrochemical sector. It is mostly organic and natural gases this kind of as alkanes and certain inorganic gases:

This kind of as carbon monoxide, there must be particular problems for a flammable gas to explode, that is: a specified concentration of flammable gas, a specified volume of oxygen, and sufficient warmth to ignite their ignition supply. These are the 3 elements of the explosion (these kinds of as the explosion triangle demonstrated in the remaining figure previously mentioned). No, that is, the absence of any of these circumstances will not cause fireplace and explosion. When combustible gasoline (steam, dust) and oxygen are mixed and attain a certain concentration, it will explode when it meets a hearth resource with a certain temperature.

We refer to the concentration of a flammable fuel as it explodes when exposed to a fire supply, referred to as the explosive concentration restrict, referred to as the explosive restrict, and is usually expressed in%. In truth, this combination does not explode at any mixing ratio but needs a focus assortment. The shaded area is revealed in the determine on the right. Explosion does not occur when the concentration of flammable gasoline is reduced than LEL (* low explosive restrict) (the focus of flammable gasoline is inadequate) and its focus is higher than UEL (* large explosive limit) (reduced oxygen).

Diverse flammable gases have diverse LELs and UELs. This need to be taken into account when calibrating the instrument. For the sake of safety, generally we must concern an alarm when the flammable fuel concentration is twenty five% or significantly less and fifty% of the LEL. Below, 25% LEL is known as the minimal limit alarm and 50% LEL is named the higher limit alarm. This is why we call the combustible gas detector the LEL detector.

The theory of the gasoline sensor: It should be famous that one hundred% exhibited on the LEL detector does not imply that the concentration of the flammable gasoline reaches one hundred% of the volume of the gasoline, but reaches a hundred% of the LEL, which is equivalent to the most affordable lower explosive limit of flammable gasoline In the case of methane, a hundred% LEL = five% quantity focus (VOL). Detection of flammable gases can be produced using semiconductor, catalytic combustion (anti-poisonous), thermally conductive and infrared sensors.

Harmful gasoline detection, at existing, for the detection of distinct harmful gases, we use the most committed gas sensors. There are 3 sorts of sensors for detecting poison gas: semiconductor variety, electrochemical kind and electrolytic mobile type.
Semiconductor sensors these kinds of as the continuous potential electrolytic variety, Galvanic battery kind, diaphragm ion electrode variety, and mounted electrolytic type have higher sensitivity and low resolution. Sensors of this basic principle have been nearly eradicated, and customers need to be very cautious when selecting this kind of sensors. Electrolytic battery sensor sound electrolyte fuel sensor employs solid electrolyte gas sensing materials as the gasoline sensing component. The basic principle is that the gasoline-sensitive materials generates ions when passing by means of the gas, thus forming an electromotive drive, and measuring the electromotive power to measure the gasoline concentration.

Owing to Trace Dew-Point Transmitters , good sensitivity and selectivity, this sensor has been widely employed, and has virtually entered into different fields this kind of as petrochemical, environmental protection, mining and other fields, 2nd only to metal oxide semiconductor fuel sensors. Such as measuring YST-Au-WO3 of H2S, measuring NH + 4CaCO3 of NH3 and so on, Electrochemical sensors are at the moment commonly used sensors for detecting toxic gases. It uses redox reactions to detect dozens of toxic gases via various electrolytes.

The basic principle of the gasoline sensor: According to the high quality of the electrolyte, its daily life is usually two to four years. The composition of an electrochemical sensor is: two reaction electrodes, a operating electrode and a counter electrode, and a reference electrode are positioned in a distinct electrolyte (as shown in the figure previously mentioned), and then a ample voltage is used among the response electrodes so that The redox reaction is performed by way of the fuel to be calculated coated with a large steel catalyst movie, and then the present generated during the gas electrolysis is measured by the circuit method in the instrument, and then the microprocessor calculates the focus of the gas.

At present, electrochemical sensors are commonly employed to detect inorganic toxic gases. Electrochemical sensors that can detect distinct gases consist of: carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrogen monoxide, nitrogen dioxide, ammonia, chlorine, and cyanogen Acids, ethylene oxide, hydrogen chloride, etc.

Detection of Risky Organic Compounds There is also a picture-ionization detector (PID) for the detection of volatile organic compounds. It can evaluate natural and organic harmful gases as minimal as ppm (and a single ten thousandth) and Vapor concentration
PID can detect most volatile natural and organic compounds (VOC). Merely put, PID can evaluate risky organic compounds with carbon figures from one (for illustration, CH2Cl2) to ten (for case in point, naphthalene). PID can be used for the basic safety and health of numerous sorts of natural and organic compound organizations that use, create, store, and transportation. At the very same time, it can also be utilised in numerous fields such as unexpected emergency mishaps in the environmental defense industry, industrial overall health consultation, public protection inspection, and chemical avoidance.

Oxygen detector Oxygen is also necessary in industrial environments, especially in shut environments. Normally, we contact the oxygen content over 23.five% as excessive oxygen (enriched oxygen), and it is straightforward to explode at this time whilst the oxygen material underneath 19.five% is oxygen deficiency (hypoxia), at this time personnel are inclined to suffocation and coma. To loss of life. The normal oxygen articles ought to be close to twenty.9%. The oxygen detector is also a kind of electrochemical sensor.

What are the Various Sorts of Oxygen Sensors?
Electrochemical oxygen sensor
Zirconia oxygen sensor
Optical oxygen sensor
Clark oxygen sensor
Infrared oxygen sensor
Ultrasonic oxygen sensor
Laser oxygen sensor
Paramagnetic oxygen sensor

Normally, the bulk of oxygen sensors measure oxygen ranges in gas or liquid utilizing 1 of three systems: optical, electrochemical or zirconia. Other oxygen measurement methods like the Clark-sort, infrared, laser, ultrasonic, radioisotope, paramagnetic, magnetic resonance and electron resonance are discovered in highly specialised industrial, health care and scientific applications.

1. Electrochemical Oxygen Sensor
Electrochemical galvanic oxygen sensors are utilised, principally, to evaluate oxygen ranges in ambient air. They measure a chemical response inside of the sensor that generates an electrical output in proportion with the oxygen level.

Some electrochemical sensors can be self-run considering that they create their possess analog present. This helps make the sensors useful for measuring oxygen fuel with battery-operated scuba diving and hand-held personalized safety.

A significant hurdle for electrochemical sensors is that, presented time, the chemical response ends. This usually takes in between one and 3 several years, depending on the design and style of the sensor. Storing the sensors in an oxygen-free of charge setting will not lengthen the lifestyle of the sensor. Nevertheless, because of to their sturdy design, low cost, and self-energy electrochemical sensors are utilized in a excellent quantity of devices.

One particular of the most prevalent manufacturers of electrochemical oxygen sensors is AlphaSense. The company’s sensors are used in dozens of four-gas detectors and portable basic safety meters employed globally.

2. Zirconia Oxygen Sensor
Zirconia oxygen sensors are a type of electrochemical sensor. Zirconia dioxide is coated with a fine layer of platinum to form a solid‐state electrochemical gasoline cell. If carbon monoxide is existing in the test gasoline, it is oxidized by O2 to kind CO2 and triggers a current. The zirconia sensor detects the variation among the focus of O2 in an exhaust fuel and in the normal air, relatively than immediately sensing the O2.

Although zirconia oxygen sensors are usually utilized in autos to regulate air-fuel ratios, they are also essential in industrial applications. As an illustration, SST’s Zirconia Oxygen Measurement Sensor Technique uses this technological innovation to evaluate the oxygen material in combustion handle methods, flue gases, oil, gas, coal, biomass and in oxygen generation techniques.



three. Optical Oxygen Sensor
Optical oxygen sensors are optochemical sensors that use the theory of fluorescence quenching by oxygen. They rely on the use of a gentle resource, a gentle detector, and a mild reactive luminescent substance. Luminescence‐based oxygen sensors are replacing the Clark electrode in a lot of locations.

The principle behind fluorescence quenching by molecular oxygen has been understood for a extended time. When uncovered to mild some compounds or molecules will fluoresce (i.e. emit mild power). Nonetheless, if oxygen molecules are present, the mild strength is transferred to the oxygen molecule leading to decreased fluorescence. By using a recognized light-weight supply, the amount of light-weight energy detected is inversely proportional to the quantity of oxygen molecules present. Consequently, the less fluoresce detected, the a lot more oxygen molecules that will be located in the sample gasoline.



Some sensors detect the fluorescence 2 times at a identified time interval. Alternatively of measuring the total fluorescence, the drop in luminescence (i.e. fluorescence quenching) above time is calculated. This time decay based mostly method enables less complicated sensor design.

The LuninOX LOX-02 is an case in point of a sensor that makes use of fluorescence quenching by oxygen to measure ambient oxygen ranges. Whilst it has the same footprint as conventional electrochemical sensors, because of to the fact it does not soak up oxygen it gives the reward of a much higher lifespan.

The TecPen Handheld Oxygen Sensor is yet another illustration. The TecPen utilizes a wonderful coating of luminescent dye on the sensor and a micro pump to pull the air sample past the fluorescing dye. The dye is excited at 507 µm and the subsequent fluorescence celebration recorded at 650 µm. This fluorescence event’s period, referred to as the life time, relies on the amount of absorbed oxygen in the sensor layer and can as a result be employed to create the oxygen concentration.

Due to the reality it employs the more rapidly optochemical sensing technology it can just take a measurement in 3 seconds.



four. Clark Electrode Oxygen Sensor
The Clark electrode is a variety of electrochemical sensor. It actions oxygen levels in liquid using a cathode and an anode immersed in an electrolyte. It was designed to measure blood oxygen ranges during cardiac surgical treatment. Presently, it is regularly utilized in portable blood glucose checking devices that require a drop of blood. The sensor uses a wonderful layer of glucose oxidase (GOx) on an oxygen electrode. The blood glucose stage can be calculated and displayed by measuring the amount of oxygen GOx consumes during the enzymatic reaction with the glucose.

5. Infrared Oxygen Sensor
Oxygen sensors that use pulse oximetry are most usually employed for earlobe or fingertip health-related devices to evaluate oxygen saturation in the human body. Infrared and crimson light-weight are each pulsed by means of a slender layer of pores and skin and measured by a photodiode. As the wavelengths of the light fluctuate, the ratio of absorption of gentle via the skin is in proportion to the quantity of oxygenated haemoglobin in the arteries.



6. Ultrasonic Oxygen Sensor
Ultrasonic oxygen sensors use sound velocity to measure the quantity of oxygen in a liquid or gas sample. In liquid, upstream and downstream sensors evaluate the pace variation between higher frequency seem waves. The variance in pace is in proportion with the amount of oxygen in the sample. In gases, the sound velocity differs as the gas’ molecular composition differs. This signifies ultrasonic oxygen sensors are helpful for oxygen generators or anesthesia ventilators exactly where the output is a recognized concentration of oxygen gasoline.

seven. Laser Oxygen Sensor
Tunable Diode Laser (TDL) oxygen sensors count on spectral examination. A laser beam at the wavelength of oxygen is directed by way of a gas sample to a photograph detector. The light quantity absorbed by the oxygen molecules is in proportion with the amount of the sample’s molecules.

eight. Parmagnetic Oxygen Sensor
Paramagnetic oxygen sensors depend on the simple fact that oxygen molecules are captivated to strong magnetic fields. In a few types a sample gasoline is brought into the sensor and passed via a magnetic area. The movement price alters in proportion to the amount of oxygen in the gas.

In a different variation of this layout the oxygen in the magnetic area generates a actual physical force on glass spheres that is measured. While Percent Oxygen Transmitters , it can be employed when a zirconia oxygen sensor cannot in industrial procedure manage purposes.

The key ingredient of a gasoline detector is a gas sensor. Percent Oxygen Transmitters can be divided into a few classes in theory:

Gasoline sensors making use of actual physical and chemical houses: such as semiconductor sort (area handle sort, volume manage type, surface likely variety), catalytic combustion type, strong thermal conductivity variety, etc.

Gas sensors utilizing physical properties: this sort of as thermal conductivity, mild interference, infrared absorption, etc.
Fuel sensors employing electrochemical properties: this kind of as continuous possible electrolytic type, Galvanic battery sort, diaphragm ion electrode sort, mounted electrolyte kind, etc.
The basic principle of gas sensors: According to the hazards, we divide poisonous and dangerous gases into two main groups, flammable gases and poisonous gases. Thanks to their distinct character and hazards, their detection techniques are also distinct.

Combustible gas Flamable gas is the most unsafe fuel encountered in industrial applications this kind of as petrochemical business. It is largely organic and natural gases such as alkanes and specific inorganic gases:
These kinds of as carbon monoxide, there must be specific circumstances for a flammable fuel to explode, that is: a specific focus of flammable gasoline, a specified volume of oxygen, and enough warmth to ignite their ignition supply. These are the 3 aspects of the explosion (this sort of as the explosion triangle demonstrated in the still left figure earlier mentioned). No, that is, the absence of any of these circumstances will not lead to fireplace and explosion. When flamable gasoline (steam, dust) and oxygen are blended and reach a specific focus, it will explode when it satisfies a fireplace source with a particular temperature.

We refer to the focus of a flammable gas as it explodes when exposed to a fireplace source, referred to as the explosive focus limit, referred to as the explosive limit, and is generally expressed in%. In simple fact, this combination does not explode at any mixing ratio but needs a concentration selection. The shaded region is proven in the figure on the correct. Explosion does not happen when the concentration of flammable gasoline is decrease than LEL (* minimal explosive restrict) (the concentration of flammable gas is insufficient) and its concentration is larger than UEL (* substantial explosive limit) (low oxygen).

Different flammable gases have different LELs and UELs. This should be taken into account when calibrating the instrument. For the sake of basic safety, generally we ought to situation an alarm when the flammable gas focus is twenty five% or much less and fifty% of the LEL. Listed here, 25% LEL is referred to as the minimal limit alarm and 50% LEL is referred to as the large limit alarm. This is why we contact the flamable gasoline detector the LEL detector.

The theory of the gas sensor: It must be observed that 100% shown on the LEL detector does not imply that the concentration of the flammable gas reaches one hundred% of the quantity of the fuel, but reaches one hundred% of the LEL, which is equivalent to the least expensive low explosive limit of flammable gas In the case of methane, one hundred% LEL = 5% volume focus (VOL). Detection of flammable gases can be produced making use of semiconductor, catalytic combustion (anti-harmful), thermally conductive and infrared sensors.

Harmful gas detection, at current, for the detection of specific harmful gases, we use the most focused fuel sensors. There are 3 kinds of sensors for detecting poison gasoline: semiconductor kind, electrochemical type and electrolytic cell type.
Semiconductor sensors such as the consistent potential electrolytic kind, Galvanic battery variety, diaphragm ion electrode sort, and mounted electrolytic kind have substantial sensitivity and low resolution. Sensors of this principle have been virtually eradicated, and users ought to be incredibly cautious when picking such sensors. Electrolytic battery sensor solid electrolyte gasoline sensor utilizes reliable electrolyte gas sensing substance as the gas sensing component. The basic principle is that the fuel-sensitive content generates ions when passing through the gas, thereby forming an electromotive drive, and measuring the electromotive drive to evaluate the gasoline focus.

Due to its high conductivity, excellent sensitivity and selectivity, this sensor has been extensively used, and has almost entered into different fields these kinds of as petrochemical, environmental security, mining and other fields, 2nd only to steel oxide semiconductor gas sensors. These kinds of as measuring YST-Au-WO3 of H2S, measuring NH + 4CaCO3 of NH3 and so on, Electrochemical sensors are presently broadly used sensors for detecting poisonous gases. It makes use of redox reactions to detect dozens of poisonous gases by means of distinct electrolytes.

The basic principle of the gas sensor: In accordance to the top quality of the electrolyte, its lifestyle is normally two to four years. The composition of an electrochemical sensor is: two reaction electrodes, a functioning electrode and a counter electrode, and a reference electrode are positioned in a certain electrolyte (as demonstrated in the determine over), and then a ample voltage is applied in between the reaction electrodes so that The redox response is done by way of the fuel to be measured coated with a hefty metallic catalyst film, and then the present produced throughout the gas electrolysis is measured by the circuit program in the instrument, and then the microprocessor calculates the concentration of the fuel.

At existing, electrochemical sensors are commonly employed to detect inorganic poisonous gases. Electrochemical sensors that can detect particular gases consist of: carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrogen monoxide, nitrogen dioxide, ammonia, chlorine, and cyanogen Acids, ethylene oxide, hydrogen chloride, and many others.

Detection of Unstable Natural Compounds There is also a photo-ionization detector (PID) for the detection of risky organic and natural compounds. It can measure natural toxic gases as low as ppm (and 1 ten thousandth) and Vapor concentration
PID can detect most unstable organic compounds (VOC). Just set, PID can measure risky organic and natural compounds with carbon quantities from one (for case in point, CH2Cl2) to ten (for instance, naphthalene). PID can be utilized for the basic safety and wellness of various types of organic and natural compound companies that use, create, retailer, and transport. At the very same time, it can also be utilised in different fields this sort of as unexpected emergency mishaps in the environmental defense market, industrial health consultation, community security inspection, and chemical prevention.

Oxygen detector Oxygen is also essential in industrial environments, specifically in closed environments. Usually, we phone the oxygen content above 23.five% as excessive oxygen (enriched oxygen), and it is straightforward to explode at this time whilst the oxygen content beneath 19.5% is oxygen deficiency (hypoxia), at this time workers are vulnerable to suffocation and coma. To death. The standard oxygen content need to be all around 20.9%. The oxygen detector is also a kind of electrochemical sensor.

OX-one oxygen sensor is also referred to as OX-one oxygen battery.
The theory of a fuel mobile is an electrochemical gadget with the same composition as a general battery. The solitary cell is composed of two electrodes (a damaging electrode is a gasoline electrode and a good electrode is an oxidant electrode) and an electrolyte. The distinction is that the active content of a basic battery is stored inside of the battery, thus restricting the battery ability. The good and negative electrodes of a gasoline cell do not include lively materials, but are only catalytic conversion components. Consequently, gas cells are genuinely vitality conversion equipment that transform chemical strength into electrical vitality. When the battery is functioning, gasoline and oxidant are provided from the outside the house and respond. In theory, as lengthy as the reactants are repeatedly enter and the reaction merchandise are repeatedly removed, the gas cell can repeatedly produce electrical power.
importance:
① Hydrogen is a multi-aspect in the planet. The source of hydrogen is incredibly extensive and it is a renewable useful resource, so it appears appropriate to use hydrogen as a “fuel”.
② Because the fuel mobile converts chemical energy straight into electrical strength, it does not produce a large volume of exhaust fuel and squander heat when compared with the combustion of the internal combustion engine, and the conversion performance can exceed fifty% (the inside combustion motor conversion performance is ten%). The emissions are only water, and Affects the ambient temperature.
③ The service life is lengthier than that of electrochemical cells and the battery maintenance workload is tiny.

④Compared to the charging time of pure electric automobiles, the time for fuel cells to fill hydrogen is extremely brief, which is almost the very same as the time for adding gasoline to inside combustion engines, about three-five minutes.
A gas mobile is an electrochemical electricity technology device. It is different from batteries in the standard sense. The primary principle is that the gasoline mobile straight converts chemical power into electrical vitality in accordance to an electrochemical approach. It does not go by means of the heat engine procedure, so it is not minimal by the Carnot cycle, and has large power conversion performance (forty-60%) it creates nearly no NOx and SOx emissions. Furthermore, CO2 emissions are reduced by more than 40% compared to typical power crops. Simply because of these outstanding advantages, the investigation and growth of gas mobile technology has obtained a lot consideration from governments and large companies in a variety of countries. It is regarded to be the desired cleanse and productive energy era technological innovation in the 21st century. When it performs, the oxidant and decreasing agent can be constantly from the exterior Enter, and at the exact same time constantly discharge the electrode response items out of the battery, straight change the chemical energy of the gasoline combustion response in the vitality source into electrical energy.It has the benefits of large energy conversion charge and sustainable use. Hydrogen gasoline cell: : O2 + 4H + + 4e- = 2H2O Total response: 2H2 + O2 = 2H2O Immediate methanol fuel mobile (DMFC) Reaction formula: Negative: CH3OH + H2O-6e- = CO2 + 6H + Good: three / 2O2 + 6H + + 6e = 3 H2O total response: CH3OH + 3 / 2O2 = CO2 + 2 H2O aluminum-air-drinking water adverse: 4Al-12e- = 4Al3 + optimistic: 3O2 + 6H2O + 12e- = 12OH- entire reaction: 4Al + 3O2 + 6H2O = 4Al (OH ) three Keywords and phrases: American GE | Oxygen Analyzer | Micro Oxygen Analyzer | OX-1 Oxygen Sensor | OX-two Oxygen Battery | OX-3 Oxygen Sensor | OX- four oxygen battery | OX-five oxygen sensor | dew level meter | biogas analyzer | headspace analyzer
Because the OX-1 oxygen sensor, OX-2 oxygen sensor and OX-five oxygen battery are trace oxygen sensors, they want to be isolated from the air and packed in nitrogen, so when not in use, they need to be kept in a nitrogen-loaded bag at all times. When you take it out, you need to put the trace oxygen sensor into the instrument right away and purge it with inert fuel. Search phrases: American GE | Oxygen Analyzer | Micro Oxygen Analyzer | OX-1 Oxygen Sensor | OX-2 Oxygen Battery | OX-3 Oxygen Sensor | OX-4 Oxygen Battery | OX-five oxygen sensor | dew level meter | biogas analyzer | headspace analyzer
In addition, when utilizing OX-one oxygen sensors including OX-two | OX-three | OX-4 | OX-five oxygen batteries, we need to spend interest to the pressure. zirconia oxygen sensor is greater to manage the stress underneath one kg, since the OX-1 oxygen sensor is inside There is a membrane, the strain will crack by means of the membrane and lead to leakage of the OX-one oxygen sensor. Any leakage is not protected by the warranty.

Avcray’s Zirconia Oxygen Sensors aid to manage or keep track of oxygen stages in Controlled Atmosphere Purposes


Several purposes need to have a system to handle or keep track of oxygen levels in an enclosed space. To alert to harmful oxygen amounts, to handle to selected levels as part of a vital process or avert the probability of combustion taking place an accurate and reputable sensor is required.

That is where SST will come in with a broad variety of oxygen sensing answers.

A assortment of housing styles, cabling and electrical connections are obtainable. As opposed to other technologies, their extended running daily life is owing to the non-depleting sensor cell technology. Electrochemical Cells Oxygen Sensor is needed and straightforward single point calibration can be performed in refreshing air.

Avcray’s Zirconia Oxygen Sensors have the potential to perform precisely in excessive environmental problems consequence in a rugged, strong and reliable sensor that is RoHS compliant.

These sensors can occur standalone or with built-in electronics, providing electronic or analogue outputs. They are the Oxygen sensing elements to your method. Or, SST can supply an intelligent device to locally handle outputs and transmit to a distant checking system.

Purposes incorporate alarming to harmful amounts of oxygen when storing or dealing with gases and substances. Sustaining low oxygen ranges in fireplace suppression methods for defending beneficial sector gear – these kinds of as servers and archives.

Prolonging the lifestyle of perishable products during transportation and storage within Managed Environment environments.

Or controlling the optimal oxygen amount inside procedures such as composting.

Avcray can operate with the client on a normal or customised remedy for gas monitoring methods.

No matter in which you are in the globe, get in contact with us and Ask The Professional Today!

Electrochemical sensors, also known as gas cells, measure percent or trace (ppm) amounts of oxygen in a gasoline or gasoline mixture and are utilised in Systech Illinois’ oxygen evaluation gear.

Optimisation of oxygen analyzers for different apps
Variations to the two of these cell kinds for measuring in hydrogen or hydrogen that contains atmospheres are also accessible. There are a amount of mobile housing kinds so the mobile can be optimised for the selected fuel investigation software.

The Principle Powering our Electrochemical Oxygen Sensors
All electrochemical oxygen sensors are of the self driven, diffusion limited, steel-air battery sort, comprising an anode, a semi-reliable electrolyte paste and an air cathode. The cell contains an enclosure that contains two electrodes, a flat PTFE tape with an lively catalyst, the cathode and a block of lead (anode). The enclosure is sealed apart from a small capillary that controls the rate at which oxygen can enter the mobile.

Oxygen enters the sensor by means of the capillary the place it arrives in speak to with the cathode, and is immediately lowered to hydroxl ions:

O2 + two H2O + four e– → four OH — (one)

These hydroxyl ions then migrate through the electrolyte to the direct anode. The hydroxyl ions react with the guide anode which is then oxidised to lead oxide.

2 Pb + 4 OH — → 2 PbO + 4 e– + two H2O (2)

As these two processes take place a present is created which can be calculated by the instrument. This existing is proportional to the oxygen concentration and qualified prospects to an exact perseverance of oxygen for gasoline examination purposes.


Oxygen Analyzer Sensor Life span
As the electrochemical reaction benefits in the oxidation of the lead anode, the electrical/chemical houses of the mobile alter, requiring periodic calibration. The oxidation of the direct anode also means the oxygen analyzer sensors have a restricted daily life. When all the obtainable lead has been oxidised the cell will no longer make an output, and should be replaced. For that reason the decrease the oxygen degree the sensor is uncovered to, the longer it will work.

Systech Illinois ppm cells measuring reduced amounts of oxygen must have lifetimes in excess of 3 years. Per cent cells, measuring air, need to have lifetimes about 5 years.

Some components of the fuel stream enhance the rate of oxidation, or sort other guide compounds, as a result shortening the daily life of the sensor. These consist of CO2 and Cl2. Gasoline streams that contains these gases ought to be avoided where attainable.

Trace Oxygen Transmitters of Oxygen Focus or Partial Stress
All Systech Illinois electrochemical cells use capillary diffusion and measure oxygen focus. Membrane sort diffusion limitations evaluate partial pressure.

Gasoline Pressure Effects Upon Oxygen Analyzers
The present produced by the mobile is proportional to the quantity portion of oxygen and this is independent of the strain of the gas. If, nevertheless the cell is subjected to a modest change in the force or modest pressure pulses, for illustration by a pump, then a transient current can be generated which will be noticed as alter in oxygen reading through on the analyzer.

When the strain changes, gasoline is compelled via the capillary barrier (acknowledged as bulkflow). This final results in an enhanced (or decreased) flux of gas to the cell and that's why a transient on the output signal. The transient swiftly settles as soon as the strain pulse is total and diffusion problems are re-established. Systech Illinois cells are equipped with an anti-bulkflow mechanism, which damps stress changes resulting in a appreciable reduction of the transient signal, and therefore a lot more correct oxygen fuel measurement.

The Impact of Force Pulses on Oxygen Measurement

Some pumps can matter the mobile to a barrage of force pulses, which conquer the anti bulkflow device and end result in an enhanced oxygen studying. In these circumstances it is necessary to layout the sample technique to minimise the pulses.

If the stress pulse is sufficiently big the cell barrier will rupture, frequently accompanied by the electrolyte leaking from the cell. Pressures as reduced as 1 Bar can trigger more than-pressure if improperly used. Care should be taken to prevent above-pressure of the cells as damage of this character is not coated by Systech Illinois’ guarantee.

Temperature Effects Upon Oxygen Analysis Tools
The electrochemical cells are sensitive to temperature, though the impact is relatively small. Modifying the temperature from +20 to –20°C will outcome in about a ten% loss of output signal. To minimise the effects of temperature change on the precision of oxygen gas measurement, the cells for some devices, eg EC900, have temperature payment constructed in. Other devices can have temperature payment fitted.

Linearity of output from Systech Illinois’ Oxygen Analyzers
The signal from a Systech Illinois mobile is:

O/P = consistent * ln[1/(1-C)]

In which C is the fractional concentration of oxygen

In apply, the output from the cells is efficiently linear up to thirty% oxygen. Oxygen concentrations previously mentioned thirty% would present difficulties equally because of to the non-linearity and also because of to reduced lifetime.


Systech Illinois’ Electrochemical Oxygen Analyzers have prolonged-time period steadiness and minimal drift
The style of the cell calls for that the cells velocity of response need to be ample for diffusion by means of the capillary and all other stages in the approach ought to be substantially faster. Systech Illinois cells have very lively electrodes so that the cells have a large exercise reserve. This is a aspect in making sure superb lengthy-phrase stability and lower drift.

Use of Hydrogen Cells in Gasoline Examination
Hydrogen cells are specially developed to have low hydrogen cross interference. They should be utilized in hydrogen and hydrogen that contains fuel streams, like gases this sort of as ethylene.

Hydrogen cells can be utilized on any other fuel streams, e.g. nitrogen, but their reduced signal output requires modification to the instrument to display the correct readings.

Correction for Carrier Gas Molecular Weight
The molecular bodyweight of the carrier or track record gas will influence the charge that oxygen can enter the cell by way of the capillary. This will end result in a diverse current output for the very same oxygen focus dependant on the carrier gasoline. Correction for this big difference will be required if the measurement provider gas is diverse from the calibration carrier gasoline.

For much more information and calculations you should download the complete discussion be aware.

Suitable gases for the oxygen measurement stream
Electrochemical cells are really tolerant of many factors in the gasoline stream requiring measurement. This makes these analyzers specifically appropriate for measurements in hydrocarbons, furnaces and soldering ovens, the place a lot of contaminants can be current. However some compounds interfere with the procedure of the cell and other folks shorten the cell life time by reacting with the parts of the mobile.

Solvents are a particular dilemma, typically they assault the cell resources, creating the capillary to swell and stop the oxygen achieving the cell. Gas streams made up of solvents ought to be prevented.

Acidic gases can interfere with the operation of the electrolyte, again preventing the oxygen from being calculated properly. Gasoline streams containing acidic or corrosive compounds need to also be avoided.

The lists below outline some of the gases that are efficiently calculated making use of Systech Illinois fuel mobile analyzers and some of the recognized difficulty gases.

Appropriate Gases
Nitrogen, Argon, Helium, Hydrogen*, Xenon, SF6, Butadiene*, Ethylene*, Acetylene*
* Use H2 cell

Specific Care Necessary Gases to Avoid
Carbon dioxide (lower concentrations only)
Carbon Monoxide* (Reduces mobile life time)
Chlorine (Cl2), Ammonia, Acetaldehyde*, Ethylene Glycol*, Formaldehyde*, Vinyl Chloride*, Methyl-dioxolane*, Hydrogen sulphide (H2S)
* Acceptable if concentration below 5ppm

For applications involving gases other than those detailed earlier mentioned, make sure you speak to Systech Illinois for tips.

Electrochemical sensors, also known as fuel cells, measure percent or trace (ppm) levels of oxygen in a gas or gas mixture and are used in Systech Illinois’ oxygen analysis equipment.

Optimisation of oxygen analyzers for different applications
Variations to both of these cell types for measuring in hydrogen or hydrogen containing atmospheres are also available. There are a number of cell housing types so the cell can be optimised for the chosen gas analysis application.

The Theory Behind our Electrochemical Oxygen Sensors
All electrochemical oxygen sensors are of the self powered, diffusion limited, metal-air battery type, comprising an anode, a semi-solid electrolyte paste and an air cathode. The cell comprises an enclosure containing two electrodes, a flat PTFE tape with an active catalyst, the cathode and a block of lead (anode). The enclosure is sealed apart from a small capillary that controls the rate at which oxygen can enter the cell.

Oxygen enters the sensor through the capillary where it comes in contact with the cathode, and is immediately reduced to hydroxl ions:

O2 + 2 H2O + 4 e– → 4 OH — (1)

These hydroxyl ions then migrate through the electrolyte to the lead anode. The hydroxyl ions react with the lead anode which is then oxidised to lead oxide.

2 Pb + 4 OH — → 2 PbO + 4 e– + 2 H2O (2)

As these two processes take place a current is generated which can be measured by the instrument. This current is proportional to the oxygen concentration and leads to an accurate determination of oxygen for gas analysis purposes.


Oxygen Analyzer Sensor Lifetime
As the electrochemical reaction results in the oxidation of the lead anode, the electrical/chemical properties of the cell change, requiring periodic calibration. The oxidation of the lead anode also means the oxygen analyzer sensors have a limited life. Once all the available lead has been oxidised the cell will no longer produce an output, and must be replaced. Consequently the lower the oxygen level the sensor is exposed to, the longer it will operate.

Systech Illinois ppm cells measuring low levels of oxygen should have lifetimes in excess of 3 years. Percent cells, measuring air, should have lifetimes around 5 years.

Some components of the gas stream increase the rate of oxidation, or form other lead compounds, thus shortening the life of the sensor. These include CO2 and Cl2. Gas streams containing these gases should be avoided where possible.


Measurement of Oxygen Concentration or Partial Pressure
All Systech Illinois electrochemical cells use capillary diffusion and measure oxygen concentration. Membrane type diffusion barriers measure partial pressure.

Gas Pressure Effects Upon Oxygen Analyzers
The current generated by the cell is proportional to the volume fraction of oxygen and this is independent of the pressure of the gas. If, however the cell is subjected to a small change in the pressure or small pressure pulses, for example by a pump, then a transient current can be generated which will be seen as change in oxygen reading on the analyzer.

When the pressure changes, gas is forced through the capillary barrier (known as bulkflow). This results in an enhanced (or reduced) flux of gas to the cell and hence a transient on the output signal. The transient quickly settles once the pressure pulse is complete and diffusion conditions are re-established. Systech Illinois cells are fitted with an anti-bulkflow mechanism, which damps pressure changes resulting in a considerable reduction of the transient signal, and thus more accurate oxygen gas measurement.

The Effect of Pressure Pulses on Oxygen Measurement

Some pumps can subject the cell to a barrage of pressure pulses, which overcome the anti bulkflow device and result in an enhanced oxygen reading. In these cases it is necessary to design the sample system to minimise the pulses.

If the pressure pulse is sufficiently large the cell barrier will rupture, often accompanied by the electrolyte leaking from the cell. Pressures as low as 1 Bar can cause over-pressure if incorrectly applied. Care must be taken to prevent over-pressure of the cells as damage of this nature is not covered by Systech Illinois’ warranty.

Temperature Effects Upon Oxygen Analysis Equipment
The electrochemical cells are sensitive to temperature, although the effect is relatively small. Changing the temperature from +20 to –20°C will result in approximately a 10% loss of output signal. To minimise the effects of temperature change on the accuracy of oxygen gas measurement, the cells for some instruments, eg EC900, have temperature compensation built in. Other instruments can have temperature compensation fitted.

Linearity of output from Systech Illinois’ Oxygen Analyzers
The signal from a Systech Illinois cell is:

O/P = constant * ln[1/(1-C)]

Where C is the fractional concentration of oxygen

In practice, the output from the cells is effectively linear up to 30% oxygen. Oxygen concentrations above 30% would present difficulties both due to the non-linearity and also due to reduced lifetime.

Systech Illinois’ Electrochemical Oxygen Analyzers have long-term stability and low drift
The design of the cell requires that the cells speed of reaction should be sufficient for diffusion through the capillary and all other stages in the process should be significantly faster. Systech Illinois cells have highly active electrodes so that the cells have a large activity reserve. This is a factor in ensuring excellent long-term stability and low drift.

Use of Hydrogen Cells in Gas Analysis
Hydrogen cells are specially designed to have low hydrogen cross interference. They must be used in hydrogen and hydrogen containing gas streams, including gases such as ethylene.

Hydrogen cells can be used on any other gas streams, e.g. nitrogen, but their lower signal output requires modification to the instrument to display the correct readings.

Correction for Carrier Gas Molecular Weight
The molecular weight of the carrier or background gas will affect the rate that oxygen can enter the cell through the capillary. This will result in a different current output for the same oxygen concentration dependant on the carrier gas. Correction for this difference will be required if the measurement carrier gas is different from the calibration carrier gas.

For more information and calculations please download the full discussion note.

Acceptable gases for the oxygen measurement stream
Electrochemical cells are very tolerant of many components in the gas stream requiring measurement. This makes these analyzers especially suitable for measurements in hydrocarbons, furnaces and soldering ovens, where many contaminants can be present. However some compounds interfere with the operation of the cell and others shorten the cell lifetime by reacting with the components of the cell.

Solvents are a particular problem, often they attack the cell materials, causing the capillary to swell and prevent the oxygen reaching the cell. Gas streams containing solvents should be avoided.

Acidic gases can interfere with the operation of the electrolyte, again preventing the oxygen from being measured correctly. Gas streams containing acidic or corrosive compounds should also be avoided.

The lists below outline some of the gases that are successfully measured using Systech Illinois fuel cell analyzers and some of the known problem gases.

Acceptable Gases
Nitrogen, Argon, Helium, Hydrogen*, Xenon, SF6, Butadiene*, Ethylene*, Acetylene*
* Use H2 cell

Special Care Required Gases to Avoid
Carbon dioxide (low concentrations only)
Carbon Monoxide* (Reduces cell lifetime)
Chlorine (Cl2), Ammonia, Acetaldehyde*, Ethylene Glycol*, Formaldehyde*, Vinyl Chloride*, Methyl-dioxolane*, Hydrogen sulphide (H2S)
* Acceptable if concentration below 5ppm

For applications involving gases other than those listed above, please contact Systech Illinois for advice.

The electrolytic moisture sensor used by Systech Illinois employs the well known phosphorus pentoxide principle for accurate determination of trace levels of moisture in inert gas streams.

Principle of Operation
The method is termed coulometric hygrometry. It is a primary standard and does not need calibration. According to Faradays law of electrolysis the current generated by electrolysis of water can de directly related to its concentration.

The phosphorus pentoxide (P2O5) moisture sensor consists of a dual platinum winding formed around a quartz tube about 8cm long. The bare platinum electrodes are coated with a thin film of P2O5. A constant DC voltage is applied across the windings and the resultant current is monitored. As the gas flows through the cell, the moisture in the gas stream is attracted to the P2O5 coating which is extremely hygroscopic. The moisture migrates through the film to the electrodes (platinum wires) where is it electrolysed. Oxygen is formed at the positive electrode and hydrogen at the negative electrode. The gases diffuse back into the gas stream where they are carried out of the cell. All of the moisture in the gas stream is consumed as it passes through the cell.


This electrolysis current, according to Faraday’s law, is directly proportional to the amount of moisture in the gas stream. Therefore, a knowledge of the gas flow rate through the sensor and the cell current gives an absolute measure of the moisture contained in the sample gas. The mathematical equation for this measurement is:

I = K1 F C + (e + B )

where:

l = Current
K1 = Faraday’s Constant
F = Mass Flow
C = Moisture Content of Gas
e = Electrolytic Background Current
B = Recombination Current

An effect called recombination can occur if the carrier gas contains hydrogen or oxygen. Recombination occurs because the hydrogen or oxygen in the sample gas stream will combine with the hydrogen and oxygen being produced during electrolysis to form another water molecule. This water molecule is attracted again to the electroydes and electrolysed again, producing a falsely high reading.

Systech Illinois analysers have selectable gas factors which allows compensation of the reading for gases causing recombination.

Cell Recoating
The P2O5 coating on the cells slowly deteriorates over time, especially for high moisture concentrations. Ultimately the cell will no longer respond to moisture and will require recoating. The cell needs to be sent back to the factory for cleaning and recoating. For maximum cell lifetime it is recommended that the cells are purged with clean, dry gas when not in use.

Calibration
Because this measurement principle is a primary measurement method, no calibration is required.

However, Vacuum gauge is important to ensure the flow rate of the gas stream remains at the factory setting. Mass Flow Controllers are available for most instruments to ensure the flow rate remains constant.

Applications
Inert gases typically used with this type of instruments include argon, nitrogen, and helium.

The applications for the moisture analyzers fall into two industrial areas:

Gas Producers: for ensuring product quality
Gas Users: process gas monitoring

Typical industries are Semiconductor manufacturing , Medical gases, Nuclear processing and Plastics.

The P2O5 moisture analyzers are not suitable for measurement of moisture in gases or gas mixtures that will react with the phosphorus pentoxide in the detection cell. Such gases include acetylene, butylene, carbon dioxide, hydrogen sulphide, and propylene. In addition, gas mixtures containing compounds which will attack the cell components must be avoided. Systech Illinois can provide special cells with a glass housing which are suitable for measurements in corrosive gases such as chlorine (Cl2) and hydrogen chloride (HCl)

Oxygen and hydrogen cause interference with the moisture measurement. Refer to “Recombination” above for further information regarding moisture measurements in these gases.

The electrolytic moisture sensor used by Systech Illinois employs the well known phosphorus pentoxide principle for accurate determination of trace levels of moisture in inert gas streams.

Trace Oxygen Transmitters of Operation
The method is termed coulometric hygrometry. It is a primary standard and does not need calibration. According to Faradays law of electrolysis the current generated by electrolysis of water can de directly related to its concentration.

The phosphorus pentoxide (P2O5) moisture sensor consists of a dual platinum winding formed around a quartz tube about 8cm long. The bare platinum electrodes are coated with a thin film of P2O5. A constant DC voltage is applied across the windings and the resultant current is monitored. As the gas flows through the cell, the moisture in the gas stream is attracted to the P2O5 coating which is extremely hygroscopic. The moisture migrates through the film to the electrodes (platinum wires) where is it electrolysed. Oxygen is formed at the positive electrode and hydrogen at the negative electrode. The gases diffuse back into the gas stream where they are carried out of the cell. All of the moisture in the gas stream is consumed as it passes through the cell.



This electrolysis current, according to Faraday’s law, is directly proportional to the amount of moisture in the gas stream. Therefore, a knowledge of the gas flow rate through the sensor and the cell current gives an absolute measure of the moisture contained in the sample gas. The mathematical equation for this measurement is:

I = K1 F C + (e + B )

where:

l = Current
K1 = Faraday’s Constant
F = Mass Flow
C = Moisture Content of Gas
e = Electrolytic Background Current
B = Recombination Current

An effect called recombination can occur if the carrier gas contains hydrogen or oxygen. Recombination occurs because the hydrogen or oxygen in the sample gas stream will combine with the hydrogen and oxygen being produced during electrolysis to form another water molecule. This water molecule is attracted again to the electroydes and electrolysed again, producing a falsely high reading.

Systech Illinois analysers have selectable gas factors which allows compensation of the reading for gases causing recombination.

Cell Recoating
The P2O5 coating on the cells slowly deteriorates over time, especially for high moisture concentrations. Ultimately the cell will no longer respond to moisture and will require recoating. The cell needs to be sent back to the factory for cleaning and recoating. For maximum cell lifetime it is recommended that the cells are purged with clean, dry gas when not in use.

Calibration
Because this measurement principle is a primary measurement method, no calibration is required.

However, it is important to ensure the flow rate of the gas stream remains at the factory setting. Mass Flow Controllers are available for most instruments to ensure the flow rate remains constant.

Applications
Inert gases typically used with this type of instruments include argon, nitrogen, and helium.

The applications for the moisture analyzers fall into two industrial areas:

Gas Producers: for ensuring product quality
Gas Users: process gas monitoring
Typical industries are Semiconductor manufacturing , Medical gases, Nuclear processing and Plastics.

The P2O5 moisture analyzers are not suitable for measurement of moisture in gases or gas mixtures that will react with the phosphorus pentoxide in the detection cell. Such gases include acetylene, butylene, carbon dioxide, hydrogen sulphide, and propylene. In addition, gas mixtures containing compounds which will attack the cell components must be avoided. Systech Illinois can provide special cells with a glass housing which are suitable for measurements in corrosive gases such as chlorine (Cl2) and hydrogen chloride (HCl)

Oxygen and hydrogen cause interference with the moisture measurement. Refer to “Recombination” above for further information regarding moisture measurements in these gases.

Avcray’s Trace Oxygen analyzer help to control or monitor oxygen levels in Controlled Atmosphere Applications

Many applications need a system to control or monitor oxygen levels in an enclosed space. To alert to hazardous oxygen levels, to control to selected levels as part of a critical process or prevent the possibility of combustion occurring an accurate and reliable sensor is needed.

That’s where SST comes in with a wide range of oxygen sensing solutions.

A variety of housing styles, cabling and electrical connections are available. Unlike other technologies, their long operating life is due to the non-depleting sensor cell technology. No reference gas is required and easy single point calibration can be performed in fresh air.


Avcray’s Zirconia Oxygen Sensors have the ability to function accurately in extreme environmental conditions result in a rugged, robust and reliable sensor that is RoHS compliant.

These sensors can come standalone or with integrated electronics, offering digital or analogue outputs. They are the Oxygen sensing components to your system. Or, SST can provide an intelligent unit to locally control outputs and transmit to a remote monitoring system.

Applications include alarming to dangerous levels of oxygen when storing or handling gases and chemicals. Sustaining low oxygen levels in fire suppression systems for protecting valuable industry equipment – such as servers and archives.

Prolonging the life of perishable products during transportation and storage within Controlled Atmosphere environments.

Or controlling the optimal oxygen level within processes such as composting.

Avcray can work with the customer on a standard or customised solution for gas monitoring systems.

No matter where you are in the world, get in touch with us and Ask The Expert Today!

What are the Different Types of Oxygen Sensors?
Electrochemical oxygen sensor
Zirconia oxygen sensor
Optical oxygen sensor
Clark oxygen sensor
Infrared oxygen sensor
Ultrasonic oxygen sensor
Laser oxygen sensor
Paramagnetic oxygen sensor
Generally, the majority of oxygen sensors measure oxygen levels in gas or liquid using one of three technologies: optical, electrochemical or zirconia. Other oxygen measurement methods like the Clark-type, infrared, laser, ultrasonic, radioisotope, paramagnetic, magnetic resonance and electron resonance are found in highly specialized industrial, medical and scientific applications.

1. Electrochemical Oxygen Sensor
Electrochemical galvanic oxygen sensors are used, principally, to measure oxygen levels in ambient air. They measure a chemical reaction inside the sensor that generates an electrical output in proportion with the oxygen level.

Some electrochemical sensors can be self-powered since they produce their own analog current. This makes the sensors beneficial for measuring oxygen gas with battery-operated scuba diving and hand-held personal safety.

A major hurdle for electrochemical sensors is that, given time, the chemical reaction ends. This usually takes between one and three years, depending on the design of the sensor. Storing the sensors in an oxygen-free environment will not lengthen the life of the sensor. However, due to their sturdy design, low expense, and self-power electrochemical sensors are used in a great number of devices.

One of the most prevalent manufacturers of electrochemical oxygen sensors is AlphaSense. The company’s sensors are utilized in dozens of 4-gas detectors and portable safety meters used globally.

2. Percent Oxygen Transmitters are a kind of electrochemical sensor. Zirconia dioxide is coated with a fine layer of platinum to form a solid‐state electrochemical fuel cell. If carbon monoxide is present in the test gas, it is oxidized by O2 to form CO2 and triggers a current. The zirconia sensor detects the variation between the concentration of O2 in an exhaust gas and in the normal air, rather than directly sensing the O2.

While zirconia oxygen sensors are typically used in cars to regulate air-fuel ratios, they are also vital in industrial applications. As an example, SST’s Zirconia Oxygen Measurement Sensor System uses this technology to measure the oxygen content in combustion control systems, flue gases, oil, gas, coal, biomass and in oxygen generation systems.



3. Optical Oxygen Sensor
Optical oxygen sensors are optochemical sensors that use the principle of fluorescence quenching by oxygen. They depend on the use of a light source, a light detector, and a light reactive luminescent material. Luminescence‐based oxygen sensors are replacing the Clark electrode in many areas.

The principle behind fluorescence quenching by molecular oxygen has been understood for a long time. When exposed to light some compounds or molecules will fluoresce (i.e. emit light energy). However, if oxygen molecules are present, the light energy is transferred to the oxygen molecule leading to reduced fluorescence. By using a known light source, the quantity of light energy detected is inversely proportional to the amount of oxygen molecules present. Therefore, the less fluoresce detected, the more oxygen molecules that will be found in the sample gas.



Some sensors detect the fluorescence twice at a known time interval. Instead of measuring the overall fluorescence, the fall in luminescence (i.e. fluorescence quenching) over time is measured. This time decay based approach enables simpler sensor design.


The LuninOX LOX-02 is an example of a sensor that uses fluorescence quenching by oxygen to measure ambient oxygen levels. While it has the same footprint as conventional electrochemical sensors, due to the fact it does not absorb oxygen it provides the benefit of a far greater lifespan.

The TecPen Handheld Oxygen Sensor is another example. The TecPen uses a fine coating of luminescent dye on the sensor and a micro pump to pull the air sample past the fluorescing dye. The dye is excited at 507 µm and the subsequent fluorescence event recorded at 650 µm. This fluorescence event’s duration, referred to as the lifetime, relies on the amount of absorbed oxygen in the sensor layer and can therefore be used to establish the oxygen concentration.

Due to the fact it uses the faster optochemical sensing technology it can take a measurement in three seconds.



4. Clark Electrode Oxygen Sensor
The Clark electrode is a kind of electrochemical sensor. It measures oxygen levels in liquid using a cathode and an anode immersed in an electrolyte. It was developed to measure blood oxygen levels during cardiac surgery. Presently, it is frequently used in portable blood glucose monitoring devices that require a drop of blood. The sensor uses a fine layer of glucose oxidase (GOx) on an oxygen electrode. The blood glucose level can be calculated and displayed by measuring the quantity of oxygen GOx consumes during the enzymatic reaction with the glucose.

5. Infrared Oxygen Sensor
Oxygen sensors that use pulse oximetry are most frequently used for earlobe or fingertip medical devices to measure oxygen saturation in the body. Infrared and red light are both pulsed through a thin layer of skin and measured by a photodiode. As the wavelengths of the light vary, the ratio of absorption of light through the skin is in proportion to the quantity of oxygenated haemoglobin in the arteries.



6. Ultrasonic Oxygen Sensor
Ultrasonic oxygen sensors use sound velocity to measure the quantity of oxygen in a liquid or gas sample. In liquid, upstream and downstream sensors measure the speed variation between high frequency sound waves. The variance in speed is in proportion with the quantity of oxygen in the sample. In gases, the sound velocity differs as the gas’ molecular composition differs. This means ultrasonic oxygen sensors are beneficial for oxygen generators or anesthesia ventilators where the output is a known concentration of oxygen gas.

7. Laser Oxygen Sensor
Tunable Diode Laser (TDL) oxygen sensors depend on spectral analysis. A laser beam at the wavelength of oxygen is directed through a gas sample to a photo detector. The light quantity absorbed by the oxygen molecules is in proportion with the amount of the sample’s molecules.

8. Parmagnetic Oxygen Sensor
Paramagnetic oxygen sensors depend on the fact that oxygen molecules are attracted to strong magnetic fields. In a few designs a sample gas is brought into the sensor and passed through a magnetic field. The flow rate alters in proportion to the level of oxygen in the gas.

In a different version of this design the oxygen in the magnetic field generates a physical force on glass spheres that is measured. While not a widespread sensing technology, it can be used when a zirconia oxygen sensor cannot in industrial process control applications.

Nowadays, automobile engines can be controlled using different types of sensors. These sensors control the performance & emissions of an engine. When Trace Oxygen Transmitters doesn’t provide accurate data then a lot of problems will occur like drivability, an increase in fuel usage, and failure of emission. One of the essential sensor used in automobiles are oxygen sensor, and the chemical formula of this is o2. The first oxygen sensor was invented in the year 1976 in Volvo 240 vehicle. In 1980, the automobiles in California used these sensors for lower emissions.

What is an Oxygen Sensor?
An oxygen sensor is one type of sensor and it is available in the exhaust system of an automobile. The size and shape of this sensor look like a spark plug. Based on its arrangement in regard to the catalytic converter, this sensor can be arranged before (upstream) or after (downstream) the converter. Most of the automobiles which are designed after 1990 include upstream & downstream o2 sensors.

The oxygen sensors used in automobiles are one sensor is arranged in front of the catalytic converter & one is arranged in every exhaust manifold of the automobile. But, the maximum number of these sensors in a car mainly depends on the engine, model, year. But, most of the vehicles have 4-sensors


Working Principle
The working principle of the o2 sensor is to check the oxygen amount within the exhaust. Firstly, this oxygen was added to the fuel for good ignition. The communication of this sensor can be done with the help of a voltage signal. So the oxygen status in the exhaust will be decided by the computer of the car.

The computer regulates the mixture of fuel or oxygen delivered to the car engine. The arrangement of the sensor before & after the catalytic converter permits to maintain the hygiene of the exhaust & check the converter’s efficiency.

Types of Oxygen Sensors
Oxygen sensors are classified into two namely binary exhaust gas and universal exhaust gas.

1). Binary Exhaust Gas Oxygen Sensor
The binary sensor gives a transition within electric voltage at 350 °C temperature based on the level of oxygen within the exhaust. It contrasts the remaining oxygen content within the exhaust by the ambient air oxygen level & recognizes the change from a lack of air to an excess air & vice versa.

2). Universal Exhaust Gas
This sensor is very exact when calculating the ratios of lack and excess of air or fuel. It has a better calculating range & is also appropriate for employ in gas &diesel engines.

Signs of Faulty Sensor
The faulty sensor can be found by using the following signs.

Breakdown to exceed the emissions analysis
Fuel mileage can be decreased.
The engine light will be off
Performance is poor, stalling and rough idling.
Code checker recognizing sensor failure
Applications
The applications of oxygen sensors include Marine Respiration, Quick Reaction Monitoring, Benchtop R&D, Monitoring of Fuel Tank, Particular Hydrocarbon Environments, Long-term Procedure Monitoring, Fermentation, Packing of Food & Beverage Packaging, Pharmaceutical & Medical, etc.

Thus, this is all about an overview of the oxygen sensor. These sensors are available in two structures like ginger type sensor and planar sensor. Here is a question for you, what are the advantages of oxygen sensor?

Electrochemical sensors, also known as fuel cells, measure percent or trace (ppm) levels of oxygen in a gas or gas mixture and are used in Systech Illinois’ oxygen analysis equipment.

Optimisation of oxygen analyzers for different applications
Variations to both of these cell types for measuring in hydrogen or hydrogen containing atmospheres are also available. There are a number of cell housing types so the cell can be optimised for the chosen gas analysis application.


The Theory Behind our Electrochemical Oxygen Sensors
All electrochemical oxygen sensors are of the self powered, diffusion limited, metal-air battery type, comprising an anode, a semi-solid electrolyte paste and an air cathode. The cell comprises an enclosure containing two electrodes, a flat PTFE tape with an active catalyst, the cathode and a block of lead (anode). The enclosure is sealed apart from a small capillary that controls the rate at which oxygen can enter the cell.

Oxygen enters the sensor through the capillary where it comes in contact with the cathode, and is immediately reduced to hydroxl ions:

O2 + 2 H2O + 4 e– → 4 OH — (1)

These hydroxyl ions then migrate through the electrolyte to the lead anode. The hydroxyl ions react with the lead anode which is then oxidised to lead oxide.

2 Pb + 4 OH — → 2 PbO + 4 e– + 2 H2O (2)

As these two processes take place a current is generated which can be measured by the instrument. This current is proportional to the oxygen concentration and leads to an accurate determination of oxygen for gas analysis purposes.


Oxygen Analyzer Sensor Lifetime
As the electrochemical reaction results in the oxidation of the lead anode, the electrical/chemical properties of the cell change, requiring periodic calibration. The oxidation of the lead anode also means the oxygen analyzer sensors have a limited life. Once all the available lead has been oxidised the cell will no longer produce an output, and must be replaced. Consequently the lower the oxygen level the sensor is exposed to, the longer it will operate.

Systech Illinois ppm cells measuring low levels of oxygen should have lifetimes in excess of 3 years. Percent cells, measuring air, should have lifetimes around 5 years.

Some components of the gas stream increase the rate of oxidation, or form other lead compounds, thus shortening the life of the sensor. These include CO2 and Cl2. Gas streams containing these gases should be avoided where possible.

Measurement of Oxygen Concentration or Partial Pressure
All Systech Illinois electrochemical cells use capillary diffusion and measure oxygen concentration. Membrane type diffusion barriers measure partial pressure.

Gas Pressure Effects Upon Oxygen Analyzers
The current generated by the cell is proportional to the volume fraction of oxygen and this is independent of the pressure of the gas. If, however the cell is subjected to a small change in the pressure or small pressure pulses, for example by a pump, then a transient current can be generated which will be seen as change in oxygen reading on the analyzer.

When the pressure changes, gas is forced through the capillary barrier (known as bulkflow). This results in an enhanced (or reduced) flux of gas to the cell and hence a transient on the output signal. The transient quickly settles once the pressure pulse is complete and diffusion conditions are re-established. Systech Illinois cells are fitted with an anti-bulkflow mechanism, which damps pressure changes resulting in a considerable reduction of the transient signal, and thus more accurate oxygen gas measurement.

Electrochemical Cells analyzer of Pressure Pulses on Oxygen Measurement

Some pumps can subject the cell to a barrage of pressure pulses, which overcome the anti bulkflow device and result in an enhanced oxygen reading. In these cases it is necessary to design the sample system to minimise the pulses.

If the pressure pulse is sufficiently large the cell barrier will rupture, often accompanied by the electrolyte leaking from the cell. Pressures as low as 1 Bar can cause over-pressure if incorrectly applied. Care must be taken to prevent over-pressure of the cells as damage of this nature is not covered by Systech Illinois’ warranty.

Temperature Effects Upon Oxygen Analysis Equipment
The electrochemical cells are sensitive to temperature, although the effect is relatively small. Changing the temperature from +20 to –20°C will result in approximately a 10% loss of output signal. To minimise the effects of temperature change on the accuracy of oxygen gas measurement, the cells for some instruments, eg EC900, have temperature compensation built in. Other instruments can have temperature compensation fitted.

Linearity of output from Systech Illinois’ Oxygen Analyzers
The signal from a Systech Illinois cell is:

O/P = constant * ln[1/(1-C)]

Where C is the fractional concentration of oxygen

In practice, the output from the cells is effectively linear up to 30% oxygen. Oxygen concentrations above 30% would present difficulties both due to the non-linearity and also due to reduced lifetime.

Systech Illinois’ Electrochemical Oxygen Analyzers have long-term stability and low drift
The design of the cell requires that the cells speed of reaction should be sufficient for diffusion through the capillary and all other stages in the process should be significantly faster. Systech Illinois cells have highly active electrodes so that the cells have a large activity reserve. This is a factor in ensuring excellent long-term stability and low drift.

Use of Hydrogen Cells in Gas Analysis
Hydrogen cells are specially designed to have low hydrogen cross interference. They must be used in hydrogen and hydrogen containing gas streams, including gases such as ethylene.

Hydrogen cells can be used on any other gas streams, e.g. nitrogen, but their lower signal output requires modification to the instrument to display the correct readings.

Correction for Carrier Gas Molecular Weight
The molecular weight of the carrier or background gas will affect the rate that oxygen can enter the cell through the capillary. This will result in a different current output for the same oxygen concentration dependant on the carrier gas. Correction for this difference will be required if the measurement carrier gas is different from the calibration carrier gas.

For more information and calculations please download the full discussion note.

Acceptable gases for the oxygen measurement stream
Electrochemical cells are very tolerant of many components in the gas stream requiring measurement. This makes these analyzers especially suitable for measurements in hydrocarbons, furnaces and soldering ovens, where many contaminants can be present. However some compounds interfere with the operation of the cell and others shorten the cell lifetime by reacting with the components of the cell.

Solvents are a particular problem, often they attack the cell materials, causing the capillary to swell and prevent the oxygen reaching the cell. Gas streams containing solvents should be avoided.

Acidic gases can interfere with the operation of the electrolyte, again preventing the oxygen from being measured correctly. Gas streams containing acidic or corrosive compounds should also be avoided.

The lists below outline some of the gases that are successfully measured using Systech Illinois fuel cell analyzers and some of the known problem gases.

Acceptable Gases
Nitrogen, Argon, Helium, Hydrogen*, Xenon, SF6, Butadiene*, Ethylene*, Acetylene*
* Use H2 cell

Special Care Required Gases to Avoid
Carbon dioxide (low concentrations only)
Carbon Monoxide* (Reduces cell lifetime)
Chlorine (Cl2), Ammonia, Acetaldehyde*, Ethylene Glycol*, Formaldehyde*, Vinyl Chloride*, Methyl-dioxolane*, Hydrogen sulphide (H2S)
* Acceptable if concentration below 5ppm

For applications involving gases other than those listed above, please contact Systech Illinois for advice.

The electrolytic moisture sensor used by Systech Illinois employs the well known phosphorus pentoxide principle for accurate determination of trace levels of moisture in inert gas streams.

Principle of Operation
The method is termed coulometric hygrometry. It is a primary standard and does not need calibration. According to Faradays law of electrolysis the current generated by electrolysis of water can de directly related to its concentration.

The phosphorus pentoxide (P2O5) moisture sensor consists of a dual platinum winding formed around a quartz tube about 8cm long. The bare platinum electrodes are coated with a thin film of P2O5. A constant DC voltage is applied across the windings and the resultant current is monitored. As the gas flows through the cell, the moisture in the gas stream is attracted to the P2O5 coating which is extremely hygroscopic. The moisture migrates through the film to the electrodes (platinum wires) where is it electrolysed. Oxygen is formed at the positive electrode and hydrogen at the negative electrode. The gases diffuse back into the gas stream where they are carried out of the cell. All of the moisture in the gas stream is consumed as it passes through the cell.


This electrolysis current, according to Faraday’s law, is directly proportional to the amount of moisture in the gas stream. Therefore, a knowledge of the gas flow rate through the sensor and the cell current gives an absolute measure of the moisture contained in the sample gas. The mathematical equation for this measurement is:

I = K1 F C + (e + B )

where:

l = Current
K1 = Faraday’s Constant
F = Mass Flow
C = Moisture Content of Gas
e = Electrolytic Background Current
B = Recombination Current

An effect called recombination can occur if the carrier gas contains hydrogen or oxygen. Recombination occurs because the hydrogen or oxygen in the sample gas stream will combine with the hydrogen and oxygen being produced during electrolysis to form another water molecule. This water molecule is attracted again to the electroydes and electrolysed again, producing a falsely high reading.

Systech Illinois analysers have selectable gas factors which allows compensation of the reading for gases causing recombination.

Cell Recoating
The P2O5 coating on the cells slowly deteriorates over time, especially for high moisture concentrations. Ultimately the cell will no longer respond to moisture and will require recoating. The cell needs to be sent back to the factory for cleaning and recoating. For maximum cell lifetime it is recommended that the cells are purged with clean, dry gas when not in use.


Vacuum gauge
Because this measurement principle is a primary measurement method, no calibration is required.

However, it is important to ensure the flow rate of the gas stream remains at the factory setting. Mass Flow Controllers are available for most instruments to ensure the flow rate remains constant.

Applications
Inert gases typically used with this type of instruments include argon, nitrogen, and helium.

The applications for the moisture analyzers fall into two industrial areas:

Gas Producers: for ensuring product quality
Gas Users: process gas monitoring
Typical industries are Semiconductor manufacturing , Medical gases, Nuclear processing and Plastics.

The P2O5 moisture analyzers are not suitable for measurement of moisture in gases or gas mixtures that will react with the phosphorus pentoxide in the detection cell. Such gases include acetylene, butylene, carbon dioxide, hydrogen sulphide, and propylene. In addition, gas mixtures containing compounds which will attack the cell components must be avoided. Systech Illinois can provide special cells with a glass housing which are suitable for measurements in corrosive gases such as chlorine (Cl2) and hydrogen chloride (HCl)

Oxygen and hydrogen cause interference with the moisture measurement. Refer to “Recombination” above for further information regarding moisture measurements in these gases.