The sensor of this circuit is a photodiode. Equivalent operations can be used, and the instrument can be replaced by the lower current range of a standard multimeter.
This circuit was found in an American documentation from the 80's. The components are from that...
The circuit shown is from the Texas Instruments optoelectronics manual. It is intended for audio...
This circuit drive an LED with constant current determined by the values of the resistors of 10...