| 摘要 |
<p>Pulse techniques are used to periodically monitor a desired environmental condition, such as pressure. A solid-state switch (14) is connected between a power source and a load. In the off state of the switch, power from the source drives a timer circuit (16) which supplies a short voltage pulse to a circuit for sensing the environmental condition. At the same time, the pulse is supplied to associated circuitry (18) for temperature compensation, amplification of the resulting sensing circuit signal, and a comparator circuit which determined whether or not a signal of the condition sensed exceeds a predetermined threshold. If such signal exceeds the threshold, the solid-state switch is turned on to connect the voltage source to the load. Turning on the switch results in substantially eliminating the voltage drop between the switch terminals, which previously was used to actuate the timer. Accordingly, a separate timer circuit (22) is provided to periodically open the closed power switch for again evaluating the sensed condition and, if appropriate, turn the power switch off. <IMAGE></p> |
