The Photohead is the sensor of an EPC (Edge Position Control) system. It uses optical means to detect the edge of a strip (web).
The sensor signal is transmitted to an amplifier, and the amplified output signal is forwarded to a hydraulic jet pipe type controller or a servo valve, controlling the strip edge, so that it remains at the determined position.
If the operating environment of the Photohead is exposed to airborne dust, or if there is the risk that oil or water droplets etc. could fall onto the Photohead projector lens, use a sensor with the air purge specification.