|
Principle of functioning
The sensitive element consists of noble metal wire coil covered with a semiconductor n-type oxide layer 30-100 m thick. The wire acts both as a heater and as a measuring electrode. The OESS operation is based on shunting the resistance of the metal wire heater with the semiconductor layer which changes its conductivity of the analyte gas.
The operation principle of this sensors enables to increase considerably both a long time stability and repeatability sensors features. The modifiing of semiconductor composition are to change sensor sensivity in detection one or another analyte gases.
|
Structure
|
 |
1 - sensitive element;
2 - racks;
3 - protective porous cap;
4 - housing;
5 - connectors;
6 - noble metal wire.
|
| Electric circuit of semiconductor sensors connection |
 |
1 - power source;
2 - ammeter;
3 - sensor;
4 - voltmeter.
|
Main technical data
On feeding the sensor with a stabilized current its output signal (ðU) arises from the difference between the voltage over the OESS element in clean air (Uair) and in the gas atmosphere (Ugas). ðU= Uair- Ugas.
Features
|
Meaning |
| Concentration range of the gases in air, % vol
|
0-100 |
| Operation current, A |
0,11±0,01 |
| Energy consumption, V*А, no more than |
0,18 |
| Responce time, s, no more than |
3 |
Lower detection limit, ppm, no more than:
methan (СН4)
carbon monooxide (СО)
propane (С3Н8)
hydrogen (Н2)
ammonia (NH3)
hydrogen sulfide (Н2S)
|
50
10
10
1
20
1
|
Relative deviation of Uair after mechanical treatment, no more than:
1000 shoks with 750 м/s2 acceleration
vibration at 250 Hz
|
0,2
0,2
|
| Weight, g |
2,5 |
| Dimension, мм |
Ø10х16 |
Semiconductor sensors are widely used in portative indicators of leakage of flammable gases, for monitoring of small concentration of toxic organic substances in ambient air.
|
