Found in a 1980s publication, this circuit can be modified to use modern components and operate at lower voltages. The power supply does not have to be symmetrical.
This simple metal finder uses a 100 uA indicator. The exploration coil must be constructed in a...
This resistance meter has a linear scale, converting resistances to voltage. The operational...
This circuit was found in a 1995 documentation. Its purpose is to indicate voltage levels that are...