This circuit was found in a 90s Electronic Engineering. The quadruple operational amplifier can be replaced by an equivalent. RL determines the tested resistance range.
The source used in this timer is of the type without transformer and regulated by the 7 W zener. The...
This circuit was found in the October 1983 Radio Electronics issue. It is applicable to old analog...
This voltmeter has an input resistance of 200 M ohms (47 M ohms resistors can be used in series to...