Sensor designed for dual purpose

01 September 2007

Omni Sensors and Transmitters, UK agents and distributors for E+E Elektronik, claims the Austrian manufacturer has achieved a world first with its HMC01.

The Coventry based agent said the product is the first true monolithic humidity/temperature sensor. The HMC01 is designed so the temperature and humidity sensors are located, one above the other, on a thin glass substrate.

Conventional combined humidity/temperature sensors usually consist of two substrates glued together, each with one sensor. This can cause practical and technical measurement problems. For example, if the two substrates separate over time the thermal connection between the two elements, very important for accuracy, will be lost.

Because of its monolithic design, the HMC01 combines the properties of the capacitive humidity sensor with the additional function of a temperature sensor on a single substrate, claimed to provide technical advantages.

The product has been designed for stable and accurate humidity and temperature measurements in demanding industrial applications. The monolithic design creates a thermal connection between the humidity and temperature element, allowing for extremely accurate measurements in moderate to high levels of humidity.

For measurement in continuous high humidity the sensor can be operated in a controlled heating mode to prevent high humidity drift. The temperature sensor is used as a heating element and is regulated in such a way that the relative humidity close to the sensor is kept at 76%RH. In this manner the sensor is not subjected to stress caused by high humidity.

The temperature sensor can also be used to regularly heat up the humidity sensor, to high temperatures, for the purpose of regeneration. This function is designed for demanding industrial process applications, where high concentrations of chemicals, solvents or cleaning agents can tarnish the sensor. Heating it up expels foreign molecules. A possible measurement drift will be corrected and the humidity sensor returns to its original calibration and starts to deliver accurate measurements again.

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