The main machine of mine vehicle mounted power-off instrument (hereinafter referred to as the main machine) is suitable for the occasion of gas and coal dust explosion in the coal mine. It is connected with the related equipment gjc4 low concentration sensor used in the coal mine to continuously monitor the gas concentration in the wind flow of the controlled area. When the gas concentration reaches or exceeds the alarm value, the sensor will immediately send out an acoustic and optical alarm signal, when the gas concentration reaches or exceeds the alarm value In case of power-off value, the main engine shall be powered off immediately (cut off the power supply of controlled equipment) to ensure production safety. When the gas concentration falls below the unlocking value, the host will automatically unlock (recover the power consumption of the controlled equipment), and continue to monitor. The host adopts intelligent single chip and new electronic devices, digital display, automatic control, stable performance, accurate threshold and quick response. The main engine has the function of automatic protection for the short circuit (fault) of intrinsically safe power supply, which ensures the safety of long-term use. The main engine also has the characteristics of small size, low power consumption, simple operation, convenient use, etc., so as to reach the advanced level of similar products in China. 2、 Technical parameters and performance of mine power-off instrument 1. Operating environment: working temperature (0-40) ℃; relative humidity ≤ 98% RH; air pressure (80-110) kPa; wind speed ≤ 8 m / S; underground coal mine with coal dust explosion risk. 2. Display mode: three digit red digital display, one digit sign display. 3. Working mode: long time continuous working V AC (factory setting at 220 V). (allowable fluctuation range: 75% ～ 115%) 5. Overall dimension: 218mm × 178mm × 102mm 6. Weight: ≤ 7 kg 7. DC output of intrinsic safety power supply of the host: 15V / 400mA DC.