This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even adapted to act as a shield. The circuit has the frequency given by C1 and adjusted in R1.
This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the...
April 2017 - Mouser Electronics is making available this new component for open LED protection...
Found in a 90s Popular Electronics, this circuit provides sinusoidal signals at frequencies given by the...