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Pepperl+Fuchs Blog

Is Environmental Heat Getting the Better of Your Optical Sensors?

Posted by Tom Anderson on Thu, Sep 24, 2015

Ed. Note: This guest blog post is by Tom Anderson, General Manager of PSI Technics, LTD. and is cowritten with Ann Zecha of WordSpark, LLC.

Radiant heat from manufacturing processes in high-temperature environments can present a challenge for optical sensors used in automated production facilities. Excessive heat in melting, pouring, or similarly demanding industrial applications that exceeds a sensor’s temperature specifications can degrade the measurement quality, damage sensor diodes, and cause unwanted disruption to production. Usage statistics show that for every 18 °F (10 °C) increase in temperature, the diode lifespan of optical sensors is reduced by up to 50%.

If you employ optical sensors in high-temperature environments, how can you ensure that the sensors in your production line continue to work reliably without having them replaced or serviced on a regular basis?

Three common options for protecting sensors in high-temperature environments are:

  • Sensor enclosures with air cooling
  • Sensor enclosures with water cooling
  • Sensor enclosures with thermo-electric cooling

Sensor enclosures with air or water cooling

The principles of air and water cooling are similar. The sensor is actively cooled by chilled air or water that flows through the surrounding enclosure. Such a cooling system usually requires a sensor jacket, an air or water supply, a cooling device, supply and discharge lines, a mounting bracket, and heat-resistant cabling. This type of cooling apparatus can be expensive and time-consuming to deploy, and ongoing costs can be high.

Sensor enclosures with Thermo-Electric Cooling (TEC)

Thermo-electric cooling also requires the sensor to be mounted inside a protective housing made of a lightweight, heat-resistant material, a mounting bracket, a power source, and heat-resistant cabling, but uses a closed-circuit cooling method. Thermo-electric cooling relies on thermally conductive components (Peltier elements) for keeping the sensor within the specified operating temperature range.

What is a Peltier element?

Thermo-electric cooling can be inexpensive to operate and this type of cooling system has fewer installation requirements than air- or liquid-cooled enclosures.

Thermo-electric cooling has the advantage that it is lightweight, maintenance-free, and does not include any moving parts or coolant supply lines, which makes the system easier to install.

Distance Sensor Mounted Inside a TEC Enclosure

A VDM100 Laser Distance Sensor Mounted Inside a TEC Enclosure

Air/water and TEC enclosures are generally sealed to IP64 (optionally to IP65) and can be equipped with a tube to eliminate interference from external light sources.

Which enclosure is right for your application?

All three methods are suitable for stabilizing optical sensors above ambient temperature. The solution that is right for you depends on a variety of considerations, such as coolant availability and maintenance cost or needs. Installing a sensor cooling system prevents sensors from malfunctioning and from having to be replaced on a regular basis in high-temperature environments. In addition, the right cooling solution can allow sensors to be used within applications that might otherwise not be possible. Download: Selecting Distance-based Photoelectric Sensors

Topics: Applications, Distance Sensors

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