Rotronic shows new range of humidity transmitters with interchangeable parts

Daniel Ritler shows how easy it is to reconfigure one of Rotronic’s new transmitters by changing the probe.

Basel, Switzerland – Daniel Ritler and his colleagues from Rotronic came to the new ”go.automation” trade fair with something new of their own to show: a series of humidity transmitters with interchangeable parts.

The basis for the new transmitters, called M series, was actually laid down four years ago, when Rotronic’s engineers developed a digital ASIC that connects with its capacitive humidity sensor. The ASIC consolidates much of the digital communications and signal conditioning electronics and allows Rotronics to package a self-contained humidity sensor system inside a small probe.

Putting all that electronics inside a probe about the size of a pencil gives more flexibility for humidity measurement, says Mr. Ritler. The probes simplify maintenance and calibration or, by changing the probe, the user can change the instrument’s application.

There are three models in the M series. The top-of-the-line M3 has an onboard microprocessor that can calculate different humidity parameters such as absolute humidity, dew-point, or enthalpy. It can also be networked on an RS-485 bus.

Rotronic developed its Hygromer capacitive polymer humidity sensor over 20 years ago. The measuring principle is based on the change of dielectric properties in the polymer as a function of the ambient relative humidity. One especially rugged version, claims Mr. Ritler, is the only humidity instrument capable of operating at 200 °C.

”We have a customer who uses it in a brick drying application,” he says. ”The temperature reaches 120°. Try doing that with any other humidity sensor!”

The M series transmitters may not go to such temperature extremes but they do have technical advantages in interchangeability and longevity that Mr. Ritler hopes will get the attention of users and systems integrators.

Control Engineering Daily News DeskMichael Babb, editor, Control Engineering Europe mbabb@reedbusiness.com

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