We found this circuit in the November 1975 issue of Radio Electronics magazine. It uses a digital module from the time with several adjustments. The power supply must have the indicated voltage.
Found in a General Electric documentation from the 1980s, this circuit makes use of a FET...
This circuit is based on an MC1408, an integrated circuit that is not common today. The...
Another way to increase the sensitivity of the circuit with the amplification of the sensor...