MONITORING OF GAS SENSORS

摘要

A monitor is disclosed for monitoring an atmosphere for the presence of a target gas having: a) a two electrode electrochemical gas sensor (11) having a working (sensing) electrode (11a) and a counter electrode (11b), the sensor providing a current between the electrodes that is indicative of the amount of the target gas in the atmosphere; b) a circuit (24, 25, 28) applying successively a pulse of positive potential between the electrode terminals and a pulse of negative potential to a point (19) causing a change of potential between the electrode terminals; and c) an operational amplifier (12) connected between the sensor electrode terminals to generate an output signal according to the current flowing between the electrodes, including pertubations therein causes by the applied pulses. A detector monitors the output of the amplifier and detects the changes in the current over the course of the pluses and generates an alarm signal when the value of the said change is less than a threshold value.