| 摘要 |
The detector element (R) is a spiral of fine Pt alloy wire in a bridge network comprising two fixed resistors (R1,R2) and two variable resistors (P1,P2) one (P1) of which is first set in the absence of gas to give the experimentally optimum voltage across the detector (R). The other variable resistor (P2) is then adjusted to set the cathode of a first diode (DS1) below its threshold voltage for a predetermined concn., with two further diodes (DS2,DS3) holding two transistors (TR1,TR2) cut off so that a relay (RL) is de-energised. Gas concn. above the preset level then provokes a voltage variation for rapid switching of the transistors and relay. |
