Photoelectric sensors �1.The photoelectric sensor �
- Photocathode is made of low work-function material → enables easy emission of electrons.
- Incident light causes electron emission, which are accelerated toward the photoanode due to applied potential difference.
- The resulting current is proportional to light intensity.
- Quantum Efficiency:
- Number of electrons emitted per photon
- Depends on photocathode material
- Materials Used:
- Metals (low efficiency)
- Cesium-based materials (high efficiency, wide spectral response: UV to IR ~1000 nm)
- Construction:
- Enclosed in vacuum or low-pressure noble gas (argon)
- Gas enhances gain via ionization collisions
- Advanced Technology (NEA surfaces):
- Uses cesium-coated semiconductor
- Operates at lower voltage compared to classical sensors
- Note: Traditional sensors require high operating voltage (hundreds of volts).