The sensor used in this circuit is uncommon today, however equivalent types can be tried. The comparator also supports modern equivalents. The circuit is from 80's documentation.
Although it is made for old oscilloscopes up to a few megahertz, this circuit converts your device...
This electrochemical circuit monitors the conductivity of the oil indicating when to change it. The...
This circuit came out in a publication called Electronics Handbook of 1993. The circuit triggers an...