APPARATUS FOR DETECTING GAS

摘要

PURPOSE:To make it possible to stably detect the concn. of gas with high accuracy, by providing a stable radiation source in the main body of a sensor for generating gaseous discharge by the application of high voltage and stably forming a negative ion (electron) by the irradiation of radioactive rays. CONSTITUTION:For example, when propane gas with concn. of 2vol% is flowed into a sensor main body 1, the number of times of gaseous discharge in the sensor main body 1 increase corresponding to the increase in the concn. of gas and a count rate detected by a pulse count circuit 12 increase. Therefore, it is discriminated that the count rate of a discharge pulse becomes larger than a reference count rate by a voltage control circuit 13 and a voltage control signal for lowering anode voltage to a high voltage power source 9 is outputted in order to suppress the count rate to the reference count rate. The number of times of discharge in the sensor body 1 are reduced by the lowering in anode voltage and feedback control for obtaining anode voltage imparting the reference count rate is performed and the concn. of gas corresponding to the controlled anode voltage is determined by a gas concn. display circuit 14 and the detected concn. of 2vol% of gas is displayed.