This circuit is from a July 1970 Radio Electronics magazine. The sensors are metal probes. The 18 V power source must be isolated from the mains.
The frequency of this oscillator depends on R and C (see math section for electronics). The...
This circuit, suggested by the Linear Applications Handbook of National Semiconductor, uses a very...
January 2017 - The new MAX14001 and MAX14002 analog to digital converters from Maxim can now be...