Dewpoint Hygrometer for Monitoring Moisture in Industrial Gases

Controlling moisture in industrial gases requires dependable measurement, particularly when processes depend on maintaining dry conditions. Water vapor that appears insignificant under normal circumstances can become important in compressed air, specialty gases, natural gas, pharmaceutical production, power generation, and other applications. Engineers and technicians need clear measurement data to understand whether gas conditions remain within the required range. A suitable hygrometer can provide this information through direct dewpoint measurement and, depending on the instrument, additional moisture units and useful data-management features. Dew-Point develops a range of moisture measurement instruments designed to help industrial users monitor low levels of water vapor in demanding applications.

What Dewpoint Measurement Tells Industrial Users

Dewpoint describes the temperature at which moisture in a gas begins to condense under the relevant pressure conditions. Unlike relative humidity, which changes significantly with temperature, dewpoint provides a practical way to describe the actual moisture condition of a gas.

This makes dewpoint measurement particularly useful when working with compressed air and industrial gases. A lower dewpoint generally indicates a drier gas, while a higher dewpoint indicates greater moisture content. By monitoring this value, operators can identify changes in drying performance and investigate unusual moisture conditions.

Dew-Point offers instruments capable of displaying dewpoint alongside other moisture measurement units, including ppm(V), ppb(V), g/m³, and lb/MMSCF on applicable models. (

Selecting a Dewpoint Hygrometer for the Application

A dewpoint hygrometer should be selected according to the measurement conditions rather than simply choosing an instrument with the widest advertised range. Gas type, pressure, expected moisture level, sampling method, operating environment, and whether measurements need to be portable or continuous all influence the appropriate choice.

Portable hygrometers can be useful for technicians who need to test several sampling points around a facility. Online instruments, meanwhile, are better suited to applications where moisture needs to be monitored continuously. Selecting equipment around the actual process requirements can help users obtain more meaningful and consistent readings.

Dew-Point's range includes portable hygrometers, transmitters, chilled-mirror instruments, sensors, and sample systems, providing different approaches to industrial moisture measurement. 

Portable Hygrometers for Field Testing

Portable instruments provide flexibility when moisture needs to be checked at multiple locations. Instead of permanently installing measurement equipment at every sampling point, maintenance teams can take a suitable handheld instrument directly to the location where testing is required.

The SADPmini2, for example, is designed for portable trace moisture measurement in industrial gases and compressed air. It includes a full-colour LCD, multiple engineering units, real-time graphing, screenshot functionality, and a rechargeable lithium-ion battery capable of more than 150 hours of continuous operation.

The SADPmini2-L adds data logging and Bluetooth/USB connectivity, allowing users to retain large quantities of measurement data for later review. It can store more than 300,000 data points, which can be useful when technicians need to document readings during inspections or maintenance programs. 

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The Importance of Sensor Technology

A moisture instrument is only as useful as the sensing technology behind it. Trace-level applications require a sensor capable of responding to small changes in water vapor while maintaining suitable stability and repeatability.

Dew-Point's portable and transmitter solutions use ultra-high-capacitance aluminium oxide sensing technology. The company's published sensor specifications cover dewpoints from approximately -110°C to +20°C, with accuracy of around ±2°C dewpoint for the listed sensor. The technology is designed for low hysteresis, stability, temperature performance, and minimal maintenance. 

This type of sensing technology is particularly relevant where moisture levels are low and conventional humidity instruments may not provide the information required for industrial process monitoring.

Sampling Can Influence Measurement Results

Obtaining a reliable reading involves more than connecting an instrument to a gas line. Sampling conditions can affect how representative the measurement is, particularly when the gas is pressurized or extremely dry.

Pressure, flow, sample tubing, temperature, and the position of the sampling point should all be considered when designing a measurement arrangement. A suitable sample system can help control these factors before the gas reaches the sensor.

Dew-Point's PSS portable sample system is designed for use with compatible handheld hygrometers. It incorporates a pressure regulator and flow indicator and can handle sample pressures up to 200 barg, helping technicians establish more controlled sampling conditions during field measurements. 

Applications for Industrial Moisture Monitoring

Moisture measurement is relevant to many industries because water vapor can affect different processes in different ways. In natural gas and LNG applications, monitoring moisture can help identify conditions associated with freezing concerns in pipelines and valves. Food and beverage operations may monitor dry gases used during packaging, while pharmaceutical facilities can use moisture measurement in applications involving inert gas blanketing and freeze-drying.

Power generation facilities can monitor gases such as hydrogen, while welding operations may check shielding gas conditions. Aerospace, medical gases, specialty gases, HDPE, and injection moulding are also among the industrial applications associated with Dew-Point's moisture measurement technology. 

Portable and Online Measurement Serve Different Needs

Not every facility requires the same type of moisture monitoring. Portable equipment is useful when measurements are performed periodically or when several locations need to be investigated. Continuous transmitters are more appropriate when operators need ongoing visibility of moisture conditions at a specific process point.

Dew-Point's AMT transmitter is designed for continuous trace moisture measurement in process gases and dry compressed air. It provides a 4–20 mA output and optional Modbus RTU communication, allowing moisture information to be connected to industrial control and monitoring systems. 

Using portable and fixed instruments together can also provide a broader monitoring strategy. A permanent transmitter can track ongoing conditions, while a handheld instrument can be used to investigate additional sampling points when required.

Hygrometers for Hazardous Environments

Industrial facilities may sometimes require moisture measurement in locations where flammable gases or potentially explosive atmospheres are present. In these situations, equipment must be selected according to the applicable hazardous-area requirements.

The SADPmini2-Ex is an intrinsically safe portable hygrometer with IECEx, ATEX, and cULus certifications. It provides trace moisture measurement, data logging, Bluetooth and USB connectivity, and an IP66/NEMA 4X-rated enclosure. 

For continuous monitoring, the AMT-Ex transmitter provides an intrinsically safe option with ATEX and IECEx certification. It is designed for continuous trace moisture measurement and can operate at pressures up to 350 bar. 

Calibration for Consistent Measurements

Calibration plays an important role in maintaining confidence in moisture measurement equipment. Regular verification can help users identify changes in instrument performance and maintain appropriate measurement records.

Dew-Point provides calibration services traceable to National and International Humidity Standards, including NPL-traceable calibration for its moisture sensors. Selected instruments also include automatic calibration or span-correction functions that can support field verification between laboratory calibrations. 

The appropriate calibration interval depends on the instrument, application, operating environment, and quality requirements of the facility. Maintaining a consistent calibration program can help ensure that recorded moisture data remains useful for process and maintenance decisions.

Choosing the Right Measurement Features

When comparing hygrometers, users should consider measurement range, accuracy, response characteristics, display options, data logging, communication interfaces, battery life, sampling accessories, and environmental certifications.

For field technicians, portability and battery life may be particularly important. Facilities requiring historical records may benefit from data logging and USB or Bluetooth connectivity. Continuous applications may instead prioritize industrial outputs such as 4–20 mA and Modbus communication.

The instrument should ultimately be matched to the process rather than selected solely according to a single specification. Understanding the actual gas conditions and measurement objectives can make equipment selection more straightforward.

Supporting Better Moisture Control

Reliable moisture information can help industrial facilities understand gas conditions, investigate unexpected changes, and support routine maintenance. Whether measurements are required during field inspections or continuously within a process, the measurement approach should provide results that are appropriate for the application.

A Dewpoint Hygrometer can provide a practical way to monitor moisture conditions in industrial gases and compressed air. With portable instruments, online transmitters, specialized sampling equipment, and calibration support, Dew-Point offers solutions that can be adapted to different measurement environments and industrial requirements.