Electrostatic-detector


Posted on Feb 21, 2013

The heart of the electroscope is the two junction FETs Ql and Q2 connected in a balanced-bridge circuit. The gate input of Ql is connected to the wire pick-up antenna, while Q2`s gate is tied to the circuit`s common ground through R2. That type of bridge circuit offers excellent temperature stability; therefore, Ql is allowed to operate in an open-gate configuration.


Electrostatic-detector
Click here to download the full size of the above Circuit.

Potentiometer R7 is used to balance the bridge circuit, and R6 sets the maximum meter swing. Capacitors Cl and C2 help to reduce the 60-Hz pickup and add to the short-term stability of the circuit.




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