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.
Found in an old Elektor, this circuit uses two 7-segment displays to indicate the volume of an...
This resistance meter has a linear scale, converting resistances to voltage. The operational...
I got this circuit from an English magazine from 1977. It can still be easily assembled, as the...