Robust humidity sensor helps keep trains moving in cold weather.

A manufacturer of safety equipment for railways relies on Michell’s Humidity and Temperature sensor, PF72-Series, to monitor and control its range of railway switch-point heating systems. ‘Points’ are the sections of track that move to switch the trains from one track to another. Because of their moving parts and exposed conditions, they are susceptible to freezing in cold weather if not heated. The heating system measures the temperature and humidity around the point so the systems can automatically react to changes in temperature and prevent the point from freezing. As with any railway application, the measurement equipment must not only be robust it also has to be extremely reliable. In addition to its primary safety function the sensor helps the customer to save energy as the heating system is only switched on when necessary and does not over-heat the area. The stainless steel PFMini72 relative humidity probes are based on the I7000 Hygrosmart relative humidity module. This interchangeable module has miniaturized electronics and does not require recalibration, instead the module is simply replaced, which can be done without specialised equipment. Because the I7000 is small, engineers can carry a supply with them and exchange them on the spot to ensure the heating system continues to operate. • Michell products are marketed in Ireland by Instrument Technology.