Liquid level switches support higher supply voltages

23rd January 2018

SST Sensing

Anna Flockett

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As it strengthens its widely-used Optomax portfolio of accurate, cost-effective and reliable infra-red (IR) liquid level switches, SST Sensing is now offering the Optomax Industrial series. These devices offer the same functionality and operational performance as customers have come to expect from standard Optomax switches, but with the added advantage of greater overall electrical robustness and flexibility.

They are capable of accepting supply voltages from 4.5-15.4VDC or 8-30VDC and have built-in protection against over-voltage, reverse polarity, and the presence of voltage transients or electrostatic discharge strikes. Delivering an output current of up to 1A, they can be used to directly activate alarm beacons, relays, pumps and motors within the system - so that reactive measures can be taken. A broad variety of electronic output configurations are available, to meet specific application requirements.

The liquid level switches can deal with pressure levels up to 20bar. In addition, industrial operating temperature ranges are supported - standard models covering -25 to 80°C and extended versions spanning all the way from -40 to 125°C. These devices have compact dimensions, measuring as little as 33.8mm in length, and come in a choice of M12, ½”-20 UNFand 1/4” NPTthread options. They are supplied in two different chemically-resistant, anti-corrosive housing options, with Polysulfone being used for the majority of applications and Trogamid being employed mainly in tasks such as food and beverage processing.

The proprietary Optomax liquid level sensing circuit developed by SST consists of an IR LED and a phototransistor, accompanied by a microcontroller unit. The strength of the IR signal passing between the LED and the phototransistor alters when liquid comes into contact with the sensor tip - thereby providing a rapid and highly precise method to determine the presence of liquid (even in the smallest of quantities) or its or absence.

The switches’ output signals can be set ‘high’ in order to correspond either to a wet or a dry state, as is most appropriate for the application and connected circuitry. As this mechanism is based on a solid-state arrangement, with no moving parts involved, it is much more reliable than alternative solutions (such as float switches). Optomax devices are, as a result, not subject to mechanical wear and tear, nor are they susceptible to jamming issues.