HV detector probe using multivibrator and indicating LEDs - detects the presence of AC potentials greater than one thousand and has in built test facilities ensuring it is serviceable before use

摘要

The voltage on the probe needle is amplified and used to hold the state of a multivibrator constant. The non-inverting output is amplified to drive a red light-emitting diode, LED. If no voltage is present, the inverting output drives a green LED via another amplifier. If the needle is not pressed into the body of the probe, an a.c. generator causes the LED's to flash alternately. When, as a test, the needle is pressed in with a finger, the green LED lights. If the finger is then used to short together the needle and an auxiliary electrode, the green LED goes out and the red one lights, due to a signal from another a.c. generator.