Reliably detecting water – with MICROmote® optical sensors from STM

Balluff STM GmbH: Clear liquids such as water cannot be detected by optical means in transparent pipes or containers without further ado. It gets especially difficult if the pipe diameter is very small or if the containers are only semi-transparent.

When using optical sensors for detection of water levels, the effects of light transmission and refraction in water can interfere with one another to such an extent that measurements are actually reversed, especially in the interaction with the container walls.

To solve this problem, the through beam sensors of the MICROmote® “JJ” series were developed by STM. The transmitters work in the upper infrared range. In the absorption spectrum of water there is at this point a maximum and the light of this wavelength is absorbed by the individual molecules.

Water thus becomes “non-transparent” for the optical system and detection is drastically simplified. Depending on the size of the sensor or the effective diameter of the beam, level detection can be attained with particular precision.

Along with high reliability in standard applications, the process demonstrates great versatility in application:

• It even functions with cloudy or milky semi-transparent containers or with varying distances between transmitter and receiver.
• Vapours containing water can also be reliably detected.
• The water content of transparent liquids can thus also be approximately determined by means of the different attenuation.

A special advantage of the optical sensors in the MICROmote® series is the extremely small design. It allows space-saving integration even in places that are difficult to access. The electronic evaluation unit in a separate amplifier with signal strength display allows comfortable setting. Micro-designs for capillaries and micro-channels are also available as special versions.