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Electrochemical Toxic Gas Sensor Technology
Substance-specific electrochemical sensors
- Gas diffusing into sensor reacts at surface of the sensing electrode
- Sensing electrode made to catalyze a specific reaction
- Use of selective external filters further limits cross sensitivity
![substance-specific electrochemical sensors substance-specific electrochemical sensors](https://sep.turbifycdn.com/ty/cdn/yhst-8480297768913/substance-specific-electrochemical-sensors.png)
Three electrode electrochemical toxic sensor
![Three electrode electrochemical toxic sensor Three electrode electrochemical toxic sensor](https://sep.turbifycdn.com/ty/cdn/yhst-8480297768913/Three-electrode-taxic-sensor.png)
Major Components of Electrochemical H2S Sensor
![Major Components of Electrochemical Major Components of Electrochemical](https://sep.turbifycdn.com/ty/cdn/yhst-8480297768913/Major-Components-of-Electrochemical.png)
Electrochemical CO Sensor Detection Mechanism
Carbon monoxide is oxidized at the sensing electrode:
CO + H2O CO2 + 2H+ + 2e-
The counter electrode acts to balance out the reaction at the sensing electrode by reducing oxygen present in the air to water:
1/2O2 + 2H+ + 2e- H2O
And the overall reaction is: CO + ½O2 CO2
4CF Signal Output: 0.07 μ A / ppm CO
Electrochemical H2S Sensor Detection Mechanism
Hydrogen sulfide is oxidized at the sensing electrode:
H2S + 4H2O H2 SO4 + 8H+ + 8e-
The counter electrode acts to balance out the reaction at the sensing electrode by reducing oxygen present in the air to water:
2O2 + 8H+ + 8e- 4H2O
And the overall reaction is: H2S + 2O2 H2 SO4
4HS Signal Output: 0.07 μ A / ppm CO
MicroCel versus 4 Series H2S and CO Sensors
![MicroCel versus 4 Series H2S and CO Sensors MicroCel versus 4 Series H2S and CO Sensors](https://sep.turbifycdn.com/ty/cdn/yhst-8480297768913/MicroCel-versus.png)
- Same "non consuming" chemistry as 4 Series sensors BUT:
- MicroCel CO sensor has better internal filter, less cross sensitivity to VOCs than CO channel of COSH sensor
- MicroCel H2S sensor based on the 4HS-LM "low methanol" electrode system (less cross sensitivity to interfering gases and VOCs)
City Technology 4 COSH Sensor
- Dual channel "COSH" sensor
- Single housing
- Two independent outputs for H2S and CO measurement
- Gas path through H2S first, CO 2nd
![City Technology City Technology](https://sep.turbifycdn.com/ty/cdn/yhst-8480297768913/City-Technology.png)
City Technology 4 COSH Sensor
![City Technology 4 COSH Sensor City Technology 4 COSH Sensor](https://sep.turbifycdn.com/ty/cdn/yhst-8480297768913/City-Technology-cosh-sensor.png)
H2S Gas Reaction:
H2S Sensing Electrode Reaction: H2S + 4H2O H2SO4 + 8H+ + 8e-
H2S Counter Electrode Reaction: 2O2 + 8H+ + 8e- 4H2O
Overall reaction: H2S + 2O2 H2 SO4
CO Gas Reaction:
CO Sensing Electrode Reaction: CO + H2O CO2 + 2H+ + 2e-
CO Counter Electrode Reaction: ½ O2 + 2H+ + 2e- H2O
Overall reaction: CO + ½O2 CO2
H2S signal output: 775 nA / ppm
CO signal output: 80 nA / ppm