| 摘要 |
<p>An automatic power turn-on circuit for a battery-powered measurement instrument. Instrument power is normally off, and when the instrument is connected to a voltage to be measured, the voltage that is sensed activates an electronic switch that in turn connects an internal battery to the processing and display circuits of the instrument. The voltage sense circuitry includes circuits for sensing either a positive or a negative voltage, and basing a driver transistor into conduction. The driver transistor in turn activates the switch to connect the battery voltage to a power supply output node. An RC network holds the switch in the "on" position for a short period of time after the voltage to be measured is removed from the inputs of the instrument. <IMAGE></p> |
