This 1965 circuit uses a Philips 4068 tube to measure extremely small charges. The circuit has as indicator a micro ammeter and the transistors are of the time.
This circuit is one of many that we have in our section. It was taken from the Electronics...
This is a bridge for the measurement of low value resistances and high values too. The circuit...
This circuit for the two-meter band of radio amateurs was found in 1980s documentation....