The model OLS-C05 optoelectronic level switch is used for monitoring the level of liquids. The optoelectronic sensor consists of an infrared LED and a light receptor.

The light from the LED is directed at a prism which forms the tip of the sensor. So long as the tip is not immersed in liquid, the light is reflected within the prism to the receiver.

When the liquid rises within the vessel and surrounds the tip, the light beam is refracted by the liquid, so that the receiver is no longer or only weakly reached by the light and reacts to this change by triggering a switching operation.

For versions with trimmer, the switching status can be read directly on the sensor (internal red LED).

The model OLS-C05 level switch is designed for use with liquids at high temperatures of up to +170 °C [+338 °F].