This circuit was found in the July 1978 issue of Radio Electronics magazine. The circuit uses a common digital voltmeter as the indicator. The sensors are integrated circuits of the time.
If the battery is good, the LED flashes. This simple tester uses an LM3909 integrated circuit. We found...
This circuit is from an old publication by A. Fanzeres. To use a unit, it is sometimes necessary to...
An interesting type of sensor for specific applications is the sensor formed by piezoelectric...