摘要 |
<p>The system uses alternate flame on/flame off periods in which the gas supply is automatically turned on or off with automatic spark ignition. A rectified supply drives a ramp generator which, in conjunction with a voltage comparator generates a saw tooth voltage wave form at an input of a second comparator where the sawtooth is compared against a DC threshold level set by the operator. When the sawtooth crosses the threshold a thyristor circuit operates a valve to supply gas to the burner, the gas being ignited by a spark plug. The spark generator is triggered by the same signal as operates the gas valve. When the sawtooth waveform returns across the threshold the gas is turned off. The relative ON/OFF times are determined by the threshold level in relation to the sawtooth waveform.</p> |