This circuit was found in an English magazine from 1977. Signal inputs and outputs must be shielded, and the circuit can be powered by battery, since its consumption is low.
This sensor circuit for currents of the order of nanoamperes was found in an American...
The sensor of this circuit is an NTC of 20 to 50 k resistance at room temperature. The circuit is from a...
This circuit is suggested by Texas Instruments in his Optoelectronics Sourcebook. The transistors...