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Optoelectronic Level Switch - Standard and High Pressure

Models OLS-S, OLS-H

Standard and high-pressure version.

Selected documents


  • Chemical, petrochemical, natural gas, offshore industries
  • Shipbuilding, machine building, refrigerator units
  • Power generating equipment, power plants
  • Process and drinking water treatment
  • Wastewater and environmental engineering

Special features

  • Temperature ranges from -269 … +400 °C
  • Versions for pressure ranges from vacuum to 500 bar
  • Special versions: High pressure, interface measurement
  • Explosion-protected versions
  • Signal processing is made using a separate model OSA-S switching amplifier


The model OLS optoelectronic level switches are used for the detection of limit levels in liquids. This is widely independent of physical characteristics such as refractive index, colour, density, dielectric constant and conductivity. Measurement is also done in small volumes.

The switches consist of an infrared LED and a phototransistor. The light of the LED is directed into a prism. So long as the sensor tip of the prism is in the gas phase, the light is reflected within the prism to the receiver. When the liquid in the vessel rises and wets approximately 2/3 of the glass tip, the infrared lightbeam into the liquid is interrupted and only a small portion reaches the receiver. This difference is evaluated by the electronics and triggers a switching operation.

The model OLS optoelectronic level switch is also available as an explosion-protected version (zone 0 and zone 1). Together with the model OSA-S switching amplifier the sensor can be used as overflow control. The instruments are very robust and designed for rough operating conditions.

The cable to the switching amplifier does not need any shield, enabling easy and economic cabling. The model OSA-S switching amplifier is operated with an intrinsically safe signal circuit. For the 19" plug-in card version, all operating elements, except for the switch for changing the alarm direction and the potentiometers for the time delay, can be accessed from the front. If incorporated in an add-on case, a transparent cover allows seeing the switching statuses.

Data Sheet

OLS-S, OLS-H Data sheet


OLS-S, OLS-H Operating Instructions