We found this circuit in the Radio Electronics Handbook magazine special edition of 1992. The circuit uses an optocoupler as an electronic potentiometer.
This General Electric circuit is from the 80's. The PUTs used in this meter are not common...
This circuit provides a power of the order of 2 W, characterized by high performance. The output...
The sensor can be made using two bare wire or two screen with a piece of tisse between them. One...