The SDT-Ex is a reliable, accurate dewpoint transmitter suitable for continuous measurement of trace moisture in industrial process gases. This compact, 3 wire, 4-20 mA, loop powered device is certified intrinsically safe to ATEX: Ex II 1 GD Ex ia IIC T4 Ga (-20 °C ≤ Ta ≤ +60 °C) and IECEx: Ex ia IIIC T₂₀₀135 °C Da (-20 °C ≤ Ta ≤ +60 °C) and suitable for use in hazardous areas using a signal isolator. The SDT-Ex dewpoint transmitter is ideal for hydrocarbon, petrochemical and hydrogen applications.

Fully self-contained within a robust housing, the SDT-Ex has been designed to cope with extreme environmental conditions. The stainless steel construction offers weatherproof protection to IP66 (NEMA 4X) with the transmitter electrical connections made via secure industrial type connector.

Utilising the ultra high capacitance SHAW moisture sensing technology and proven over many years, the sensor technology from SHAW offers superior sensitivity, repeatability and speed of response. Various dewpoint ranges are available covering an overall range from -100 °C to +20 °C (-148 °F to +68 °F) dewpoint.

Loop powered by a 7 V to 28 V DC source, the 4-20 mA output is configurable in °C dewpoint, °F dewpoint, ppm(v), g/m³, lb/MMSCF and has an accuracy of ±2 °C (±3.6 °F) dewpoint.

The SDT-Ex also incorporates the SHAW AutoCal function, where the sensor can be exposed to any atmosphere which is wetter than the operating range of the dewpoint sensor. Allowing users to ensure accuracy between annual laboratory calibrations by checking the span of the hygrometer and correcting for any deviation. AutoCal can be carried out in situ and without any special equipment. This useful feature reduces downtime, minimizes calibration costs, gives immediate verification of the dewpoint system and allows users to ensure optimum measurement accuracy between laboratory calibrations.

The transmitter can withstand 35,000 kPa (350 bar) maximum pressure and by employing low resistance cable can be located at significant distances up to 1,000 metres away from the data collection point whilst maintaining signal integrity.

For ideal sampling conditions, the SDT-Ex is compatible with the SU4 sample system, which is designed for continuous inline measurements, reducing process line pressure from the dryer to give a flow suitable for measurement and allowing the sensor to operate at atmospheric pressure. The SU4 combines a pressure regulator, sensor holder and flow meter for up to 10 litres per minute, mounted on a back plate. Other optional items include a loop powered display and signal isolator.