A device that converts a continuous direct current signal into a pulsating alternating current signal using a light source and a photoresistor or photodiode. By physically or electronically pulsing the light, the resistance of the receiving element changes rapidly, modulating the DC signal so it can be amplified by AC-coupled circuits without suffering from DC drift.
Heard on the job
The old lock-in amplifier uses a mechanical photochopper to modulate the sensor output before the first gain stage.
Also heard as
- optical chopper