| 摘要 |
<p>A flame detection circuit has means (1) for producing a flame signal indicative of the presence of a flame. The flame signal is converted to binary, two level, form by an inverting Schmitt trigger 2 whereby a logic "1" level indicates nominal flame failure. The binary flame signal is sampled at a sampling rate set by a clock pulse generator (30) and four successive samples stored in a shift register (31) of a flame signal filter (3). The filter filters out spurious indications of flame failure. An AND gate (32) produces a flame failure signal only if all four samples in the shift register have logic value "1". In this way individual "1"s do not produce spurious flame failure indications. An ignition circuit (9) responds to the flame failure signal to reignite the flame. <IMAGE></p> |
