Ados - Model GTR 196 -Gas Transmitter

The TGS sensor contains a semiconductor sensor, which is constructed on SnO2-sintered N-substrate. When combustible or reducing gases are absorbed by the surface of the sensor, the concentration of the test gas is determined by the change in conductivity.

1 = Circuit Voltage
2 = Heating Voltage
3 = Load Resistor

The head of the VQ sensor functions on the principle of heat reaction. When combustible or reducing gases or vapours come in contact with the measuring element, they are subjected to catalytic combustion, which causes a rise in temperature; this rise causes a change in the resistance of the measuring element which is used as a measure of the component of gas being tested.

The inert element is for compensating the temperature and conductivity of the test gas.

1 = Catalyzer pellistor
2 = Electric connections
3 = Inert pellistor
4 = Diffusion filter

The TOX sensor is a measurement system with an electro-chemical cell, where the sampled gas is measured by diffusion. In the case of oxygen measurement the oxygen content is reduced in an electrolyte, thus producing a small flow of current (electro-chemical process). At a constant air pressure, this current is directly proportional to the oxygen concentration in the sampled air.

1 = Anode
2 = Electrolyte
3 = Cathode
4 = Diffusion path
5 = Diffusion filter
6 = Test gas

The GOW sensor functions on the principle of thermal conductivity. Two rhenium-tungsten resistors are used as a measuring element, where the comparison element is subjected to normal ambient air and the measuring element is subjected to the test gas. Any change in the concentration of gas at the measurement element causes a change in temperature, which is due to the variation of conductivity.

The resultant change in resistance is a direct measure of the gas concentration.

1 = Disffusion filter
2 = Test resistor
3 = Comparison resistor

The test gas flows through a measurement chamber that incorporates an IR radiating source and a two-channel infrared detector. The intensity of the infrared radiation is reduced as it passes through the gas molecules. The concentration of the gas can then be calculated by the magnitude of the reduction in intensity. Since only absorption of the wavelength (A) specific to the gas under test in relation to the wavelength (B) not absorbed by a test gas is considered, interference due to dust, ageing etc., is almost fully compensated.

1 = Infrared-radiation source
2 = Test gas
3 = Diffusion filter
4 = Infrared-detector
5 = Measurement chamber