This circuit was found in an American 1980s documentation. It analyzes the exhaust gas of a vehicle using a special sensor. The indicator is a milliamperimeter.
We found this measurement circuit with a logarithmic scale in an Electronics Now from November 1995....
This circuit assumes that a pulse produced by S1 has a constant duration determined by R1 and C1....
This circuit is used for remote current monitoring. In the original version of the 80s a lamp is...