| 摘要 |
<p>PURPOSE:To surely and rapidly detect the generation of a noise by converting a DC gas concn. signal to form a mimic AC gas concn. signal and forming the differential signal between this signal and the AC gas concn. signal obtd. after one period thereof. CONSTITUTION:The AC gas concn. signal (a) is obtd. from a detecting section A and is subjected to synchronous current rectification B and synchronous smoothing C at every one period to obtain the DC gas concn. signal (delayed by one period from the signal (a)) (b). A mimic signal forming circuit F forms the mimic AC gas concn. signal (c), i.e. the signal (c) which is delayed by one period from the signal (a) and is superposed with noise component in the smoothed form even when this component is superposed thereon by multiplying 8 the signal (b) by the synchronizing signal inputted from a phase shift circuit 7. The signal (c) and the actual signal (a) are subtracted 10 in a comparing and deciding circuit G. The differential signal (d) obtd. in such a manner is compared 11 with the threshold V. The generation of the noise is decided 11 when the signal (d) exceeds the threshold V. A hold signal (e) is then emitted to open a normally closed switch SW during this time, by which the signal (b) superposed with the noise component is discarded.</p> |
