INFRARED THERMOCHEMICAL GAS AND VAPOR DETECTOR STUDY

The results of experimental study of the thermochemical gas and vapor detector (ITCGVD) are given. Functional principle of this detector is based on the measurement of infrared radiation intensity formed during catalytic combustion of flammable gases and vapors on the pellistor surface. The ITCGVD scheme is described. It contains the measuring and the comparing cells equipped with pellistors and infrared diodes working in photogalvanic mode and a counter connected ensuring their signal difference formation, which is registered after amplification by a potentiometer. The dependences of ITCGVD signal on most important parameters were determined as a result of experimental study with use of impulse method of analyzing gases input. These parameters are as follows: analyzing gas concentration in carrier gas (air) flow, a pellistor supply voltage, a distance of a pellistor from infrared photodiode window, carrier gas flow rate. The possibility of ITCGVD use in alerters and analyzers of flammable gasses and vapors micro concentration in air was determined. Experimental correlation of detector signal to hydrogen, methane and propane volume concentration in air was developed. Possibility of ITCGVD application in gas chromatography by using the analysis of calibration gas-air mixture is shown. Basic metrological characteristics of ITCGVD were determined. They are as follows: sensitivity threshold 4 . 10–5 volume percent, maximum concentration within a linear statistical characteristic – 0.4 volume percent; linear dynamic range 1 . 104; the drift of apparent zero signal – 0.6 mV/h; time constant 0.3…1 s (depends on carrier gas flow). Measuring and comparing cell volume was 0.3 ml.