SHAW Superdew 3 Inline Dew Point Hygrometer

A panel-mounted inline hygrometer for dew point in process gases and compressed air

The SHAW Superdew 3 is a single-channel inline hygrometer for measuring dew point in process gases and compressed air, with a DIN-style panel-mount enclosure protected to IP54 at the front. It pairs a SHAW aluminium oxide dew point sensor with digital electronics, and each sensor is calibrated to give a system accuracy better than plus or minus 2 degrees C dew point with a calibration certificate traceable to international standards. A five-character LED display can be set to degrees C, degrees F, ppmV or lb/MMSCF. Two programmable alarm relays and an isolated 4-20 mA output are standard, and the instrument can be sited more than 1,000 metres from the sensor.

Technical specifications

Ordering and package contents

The order code follows Superdew 3 – (R) – (U) – (V) – (F): sensor range letter, display units, supply voltage and fitting size. A Superdew package is configured to the customer specification and consists of the inline analyser, the SHAW dew point sensor, a sensor holder and 2 m of cable. Sensors and ranges are fully interchangeable, and the AutoCal feature allows a span check using a potentiometer on the front panel. The SU4 sample conditioning unit combines a pressure regulator, flow indicator and sensor holder to reduce dryer pressure to a level suitable for measurement.

Selection and documents

Choose the range letter from the lowest dew point expected, and confirm the sample pressure, the alarm settings, the supply and whether the sensor needs a hazardous-area solution, since the Superdew 3 data sheet lists CE and UKCA approvals only. For a hazardous-area transmitter see the SHAW SDT-Ex; related items are under Gas Analyzer Systems. The attached SHAW Superdew 3 data sheet holds the full specification and ordering table.

How the SHAW Superdew 3 works

The dew point is the temperature at which the water vapour in a gas starts to turn into liquid. The SHAW sensor has a thin aluminium oxide layer between two electrodes. Water vapour in the gas enters the pores of the layer and changes its electrical impedance in a way that follows the vapour pressure. The Superdew 3 electronics read this signal and show the dew point on the display, in degrees C, degrees F, ppmV or lb/MMSCF.

Where the SHAW Superdew 3 is used

• Compressed air dryers and air systems
• Natural gas and process gas lines
• Industrial gas production
• Heat treatment and welding gases
• Instrument air and plant air quality checks

Selection checklist for the Superdew 3

• Sensor range: P, S, G, R or B type
• Dew point range needed, down to -100 degrees C
• Operating pressure up to 350 bar
• Sample flow of 2 to 5 litres per minute
• Supply of 90 to 250 VAC or 24 VDC
• Alarm relays and the 4-20 mA output
• Distance between sensor and panel unit
• Cut-out of 138 x 68 mm for the panel

Installation, commissioning and maintenance notes

Fit the sensor in the sample block and take a clean, dry sample from the process line, with the flow set in the stated range. Use short stainless steel tubing, because long or plastic lines hold moisture and slow the reading. Connect the sensor with the coaxial cable and wire the alarm and 4-20 mA signals. Keep the filter clean, and have the sensor re-calibrated at the interval the plant quality system requires.

Requesting a quotation for the SHAW Superdew 3

Please send the sensor range, the gas, the line pressure and the output signals needed. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

Superdew 3 accuracy

The system accuracy is better than plus or minus 2 degrees C dew point, and the repeatability is better than plus or minus 0.3 degrees C.

Superdew 3 response

Moving from wet to dry, from -20 to -60 degrees C, takes under 120 seconds. Moving from dry to wet takes under 20 seconds.

Superdew 3 outputs and alarms

The isolated output is 4-20 mA or 0-20 mA, and two changeover alarm relays are rated 10 A at 240 VAC.

Superdew 3 case

The ABS case measures 144 x 72 x 116 mm and the front panel is rated IP54. The wetted parts are 316 stainless steel with a 50 micron sintered filter.

Dew point records for Superdew 3

Keep the sensor serial number, the alarm settings and the calibration dates with the instrument file.