SHAW SDHmini-Ex Intrinsically Safe Portable Hygrometer
Overview
The SHAW SDHmini-Ex is a hand-held, intrinsically safe dewpoint meter from Shaw Moisture Meters (UK) Ltd for fast spot-check measurement of dewpoint and trace moisture in gases and compressed air. Certified to ATEX, IECEx and UL standards for hazardous areas, it combines the SHAW ultra high capacitance aluminium oxide sensor, the AutoCal automatic calibration facility and a desiccant dry-down chamber in a robust portable housing weighing less than 1.75 kg. Accuracy is ±2 °C dewpoint, and five sensor ranges cover dewpoints from -100 to +20 °C.
Seven Star LLC supplies the SHAW SDHmini-Ex to gas producers, power utilities, compressed air users and instrument service companies in Oman and the GCC. From Muscat we provide engineering support, including sample connection fittings, service kits and advice on sampling practice for natural gas, nitrogen, instrument air and other dry gases.
Measurement Principle
The SHAW SDHmini-Ex uses an aluminium oxide capacitance sensor. In general, water vapour from the sample gas is adsorbed into the porous oxide layer of such a sensor and changes its capacitance in proportion to the partial pressure of water, which the instrument converts into dewpoint or moisture content. SHAW sensors are manufactured to saturate with water vapour at their design maximum, so when a sensor is exposed to air wetter than its range, it quickly reaches equilibrium and stops responding to further moisture. That saturation point is the basis of AutoCal: by lifting the desiccant chamber and exposing the sensor to room air, the user performs a field calibration or span check in situ without special equipment.
Between tests the sensor sits inside a chamber surrounded by desiccant and isolated from ambient air, so it stays dry and ready. For a reading, the head is raised from the dry-down position to the read position. The chamber design lets the sample gas purge the void space and walls before the sensor is exposed, which SHAW states gives faster, more accurate and reliable spot checks. Response time is less than 120 seconds from -10 to -60 °C (wet to dry) and less than 20 seconds from -100 to -20 °C (dry to wet).
Engineering Design of the SHAW SDHmini-Ex
The SHAW SDHmini-Ex housing contains the signal conditioning circuitry, memory and a full-colour 320 x 240 graphics LCD with a secondary display. Overall dimensions are 97 mm wide, 147 mm deep and 211 mm high (259 mm with the head extended), with an IP66 and NEMA 4X weatherproof rating. A rechargeable lithium-ion battery provides more than 150 hours of use between charges, with a 12-hour full charge. Users can select °C, °F, ppm(V), ppm(w), g/m³ or lb/MMSCF, and an integral calculator displays pressure dewpoint from gauge pressure entered in kPa, kg/cm², bar or psi.
The SHAW SDHmini-Ex data logger stores 300,000 date and time stamped readings across 20 user-defined location IDs, with sampling rates from every five seconds to once a day. Data can be reviewed on the instrument or transferred over USB or Bluetooth to the SHAW SDHmini User Tool software, and a Bluetooth mobile printer is available. The menu supports ten languages. Maximum operating pressure at the SHAW SDHmini-Ex sensor is 0.3 bar (4 psi), the sample flow is ideally 2 to 5 litres per minute, and the sensor is protected by a 50 micron 316 sintered stainless steel filter.
Key Features
Reasons users choose the SHAW SDHmini-Ex:
- Intrinsically safe certification: ATEX and IECEx II 1 G Ex ia IIC T4 Ga, and UL Class I Div 1 Groups A, B, C and D T4.
- AutoCal automatic calibration that can be performed in the field by any user.
- Desiccant dry-down assembly for rapid, repeatable spot checks.
- Accuracy of ±2 °C dewpoint, NPL traceable from -90 to +20 °C, with repeatability better than ±0.3 °C.
- Five sensor ranges between -100 and +20 °C dewpoint, up to 23,000 ppm(V).
- Logging of 300,000 readings with USB and Bluetooth transfer and printing.
- Over 150 hours of battery operation and a weight under 1.75 kg.
- Supplied with a Certificate of Calibration traceable to national and international humidity standards at NPL.
Industrial Applications
The SHAW SDHmini-Ex is used for natural gas dewpoint checks at wellheads, gas processing plants and custody points, for verifying desiccant and refrigerant dryers on instrument air systems, for checking nitrogen purity at generators and in pipelines, and for monitoring hydrogen-cooled generators and SF6-insulated equipment in power plants. Because it is certified intrinsically safe, it can be carried into hazardous areas at oil and gas facilities in the interior of Oman and at refineries and LNG plants on the coast where portable equipment must carry an intrinsically safe rating, subject to the area classification and site rules.
Seven Star LLC supplies the SHAW SDHmini-Ex with sample hoses, fittings and pressure regulators, and also supplies fixed moisture instruments for continuous duty. On this site you can find the SHAW SADP-P automatic dewpoint meter, the Michell Instruments Easidew EA2 dew point transmitter and the Panametrics HygroPro II aluminum oxide moisture transmitter for permanent installations.
Technical Specifications
Specifications for the SHAW SDHmini-Ex below come from the SHAW datasheet SDHmini-Ex Iss1.6:
| Parameter | Specification |
|---|---|
| Model | SDHmini-Ex portable hygrometer |
| Sensing element | SHAW ultra high capacitance aluminium oxide sensor |
| Ranges (dewpoint) | P: -100 to 0 °C; S: -100 to -20 °C; G: -80 to 0 °C; R: -80 to -20 °C; B: -80 to +20 °C |
| Accuracy | ±2 °C dewpoint, NPL traceable -90 to +20 °C |
| Resolution | 0.1 °C / 0.1 °F dewpoint or 0.1 ppm(V) |
| Response time | below 120 s wet to dry (-10 to -60 °C); below 20 s dry to wet (-100 to -20 °C) |
| Sample flow | 2 to 5 l/min ideal, 10 l/min maximum |
| Operating pressure | 0.3 bar (4 psi) maximum |
| Hazardous area certification | ATEX/IECEx II 1 G Ex ia IIC T4 Ga; II 2 D Ex ia IIIB T60°C Db; UL Class I Div 1 Groups A, B, C, D T4 |
| Approvals | CE and UKCA |
| Display | Full-colour graphics LCD, 320 x 240 |
| Data logging | 300,000 readings, 20 location IDs |
| Communication | USB and Bluetooth |
| Battery | Rechargeable Li-ion, over 150 h use; 12 h full charge |
| Operating temperature | -20 to +50 °C |
| Protection | IP66, NEMA 4X |
| Dimensions | 97 x 147 x 211 mm (259 mm head extended) |
| Weight | 1.75 kg |
| Sample connection | 1/4 in, 6 mm or 1/8 in Swagelok compression, or fir tree for 6 mm PTFE tube |
How to Order
To order the SHAW SDHmini-Ex, tell Seven Star LLC the required range code, inlet connection and mains plug type, for example SDHmini-Ex-G-6-UK. You can download the SHAW SDHmini-Ex datasheet from this page. Our Muscat instrumentation team will confirm availability and lead time, arrange calibration documents and support customers across Oman and the GCC.
- Datasheet SHAW SDHmini-Ex Portable Hygrometer Datasheet (Iss 1.6) Download
SHAW dewpoint meters and how they are used
The SADP is a portable hygrometer for spot checks. A small sample flow passes over the sensor in the instrument head, which is kept dry between tests, and the reading is taken at the sample point. Typical checks are instrument air after a dryer, nitrogen and other industrial gases, natural gas, and welding or cryogenic gases. SHAW also makes the hand-held SDHmini and the intrinsically safe SDHmini-Ex, the fixed Superdew 3 hygrometer and the AcuDew and SDT-Ex dewpoint transmitters for continuous measurement.Ordering a SHAW dewpoint meter: what we need
A SHAW meter is defined by its sensor range. State the driest and wettest dewpoint you expect, the gas, the line pressure at the sample point and the display units wanted (°C or °F dewpoint, ppm). For a replacement or a spare sensor, send the model and serial number from the instrument label. We supply to the GCC and provide the manufacturer's documents on request.Browse SHAW Instruments products by category: Gas Analyzer Systems.
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