a gas detection instrument comprises a combustible gas sensor and associated circuitry , which supplies power to the sensor and measures and displays resulting sensor response . the supplied power is switched between timed pulses of electricity and steady state electricity , with the intermittent electricity being employed only when no significant change in sensor output has been detected . alternatively , timed pulses of electricity are maintained , and predictive software algorithms are used to give readings for gas concentration during interruption of the power supply . the sensor operation enables the instrument to respond to rapid changes in gas concentration while minimizing power consumption of the sensor .