Optoelectronic switches

Featuring a compact design, high media compatibility

Optoelectronic switches are used for the detection of limit levels in liquids. The detection is widely independent of physical characteristics of the liquids such as density, dielectric constant, conductivity and refractive index. The instruments are notable for their compact design and do not feature any moving components. With a measuring tip from borosilicate or quartz glass, and robust stainless steel cases, they offer a high media compatibility.

Where are optoelectronic sensors used?

The optoelectronic level switch is used for level detection for liquids. Due to the variety in designs, the use of optoelectronic sensors is suitable for many industries. The determination of the level with the cone tip is, across wide ranges, independent of physical characteristics such as refractive index, colour, density, dielectric constant and conductivity. The measurement procedure is thus not influenced by the properties of the liquid and offers high media compatibility. They are mostly used in industrial applications, the food and beverage industry or even the pharmaceutical industry.

Which types of optical sensors are there?

WIKA offers the appropriate optoelectronic level sensor (also known as an optical sensor for short) for every application. The model OLS-C20 optoelectronic level switch is suitable, due to its compact design, for high-pressure designs, whereas the model OLS-F1 is particularly suited to sanitary applications. WIKA also offers suitable optoelectronic sensors for refrigeration technology or the shipbuilding industry. The model OLS-C51 level switch, as an explosion-protected version, is suitable for use in extreme environments.

How does an optoelectronic sensor work?

The most important components of an optoelectronic switch are the glass prism and an LED light source. Inside the glass prism there is a transmitter, a receiver and an infrared light. The light from the LED is shone into the glass prism, causing infrared light to reach the receiver. So long as the tip does not come into contact with the liquid to be measured, the light is reflected within the prism to the receiver. However, if the liquid in the container rises and envelops the tip of the optoelectronic switch, the light is refracted by the glass prism into the liquid and no longer reaches the receiver, or only very weakly. The switch then outputs this change as a modified switching signal and the LED display lights up. If the liquid in the vessel then drops again and the glass prism is no longer covered by liquid, the infrared light is also able to reach the receiver again and the LED display goes out. Learn more about how optoelectronic sensors work in our video “WIKA - Level monitoring with optoelectronic switches”.


What are the benefits of optoelectronic switches in level measurement?

  • Recording of the level with the cone tip is independent to a large extent of the physical characteristics of the liquids such as density, dielectric constant, conductivity, colour and refractive index
  • Detection of interface layers with rounded tip
  • T ...