This capacitive sensor that operates with a high frequency oscillator was found in Radio Electronics from the 90's. The circuit operates around 300 kHz.
This circuit consists of a single Hartley oscillator using a bipolar transistor that can generate...
We found this circuit in a documentation about SCRs from the 70s. The circuit can be implemented with a...
This circuit was obtained in an old documentation, making use of an operational amplifier of the...