This electrochemical circuit monitors the conductivity of the oil indicating when to change it. The circuit is from an 1967 American documentation.
This circuit using components that are still common in our market was found in a 1987...
This circuit was obtained in a 1998 publication, but it can be easily assembled. The circuit...
Found in a 73 magazine for radio amateurs of the 90s, this circuit provides a 2 kV voltage with 7.5...