This electrochemical circuit monitors the conductivity of the oil indicating when to change it. The circuit is from an 1967 American documentation.
This circuit is based on a Texas Instruments LinMOS integrated circuit consisting of an...
This sophisticated logic probe for 5 to 12 V circuits (CMOS and TTL) was found in a 1980s...
This 2005 Linear Technology circuit has separate outputs for monitoring the charge and discharge...