Published in a PE Hobbyst Handbook of 1991, this sensor uses an integrated circuit that is unusual today. The circuit is based on a high frequency oscillator.
This circuit uses an LM339 and was found in the July 1995 Electronics Now magazine. The LED lights...
We found this measurement circuit with a logarithmic scale in an Electronics Now from November 1995....
I can be obtained from Mouser Electronics the new TDK inducers SPM-LR series to currents from 1.3...