Friday 26 July 2013

Reliable RH measurement in ultra-harsh conditions

When a European OEM customer needed a reliable RH and temperature probe that would stand up to highly challenging and corrosive conditions, they contacted Michell Instruments for a solution.

Michell’s PCMini52 RH and temperature probe is designed specifically for harsh environments. Its electronics are potted to provide protection from the surrounding atmosphere which means it can survive for longer in aggressive atmospheres than comparable products. However, the OEM customer wanted to provide extra reliability and low-maintenance for its customers so they asked Michell to adapt the measuring element filter of the PCMini52 to meet its specifications.

While the calibrated performance of a sensor is important, in practical factory-floor applications, mechanical protection and strength of the humidity filter around the measuring elements also play a vital role in successful measurements, and this is what Michell’s team of custom-build engineers focused their attention on. They designed a simple, mechanical protection system to enable the PCMini52 to withstand the ultra-harsh conditions demanded by the OEM.

The application involved high levels of condensate surrounding the probe, so the main challenge was to prevent ingress into the probe at the joint of the filter assembly. The solution was deceptively simple: an alternative filter guard for the sensing head was engineered to reduce the possible points of ingress for condensate and provide extra strength and protection. The filter protection cap was also designed to visually indicate contamination, which acts as an additional fail-safe for the process.

The new filter is now available as an option on the RH probes from Michell Instruments.

• Mitchell Instruments are marketed in Ireland by Instrument Technology.

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