Moisture control can be an important part of maintaining reliable industrial processes, especially when gases or compressed air must remain within specific dryness limits. Small quantities of water vapor may not be visible, yet they can influence equipment, process conditions, gas quality, and overall system performance. Reliable measurement gives operators a clearer understanding of moisture conditions and allows changes to be identified before they become more disruptive. For this reason, industrial facilities often require measurement solutions that can detect low levels of moisture with suitable accuracy and repeatability. Dew-Point provides precision-engineered instruments, online systems, sensors, sample systems, and accessories designed for trace moisture measurement in process gases and dry compressed air.
Why Trace Moisture Analysis Matters
Trace moisture measurement is particularly valuable when a process depends on maintaining dry gas conditions. Moisture levels can change because of variations in gas supply, drying equipment, temperature, pressure, or operating conditions. Without appropriate monitoring, these changes may not become apparent until they begin affecting a process or piece of equipment.
Online measurement systems can provide continuous information, while portable instruments allow technicians to perform spot checks at different locations. Using the appropriate approach helps facilities understand whether moisture levels remain within the required operating range and provides useful information for maintenance and process decisions. Dew-Point’s product portfolio includes portable, online, transmitter, sample-system, and chilled-mirror solutions for different measurement requirements.
How a Trace Moisture Analyzer Supports Process Monitoring
A trace moisture analyzer is designed to determine very small quantities of water vapor in gases or compressed air. Depending on the instrument and application, results can be presented as dewpoint temperature or absolute moisture units such as ppm(V), ppb(V), g/m³, and lb/MMSCF.
The measurement method and instrument configuration should be selected according to the gas, required range, pressure, sampling conditions, and whether the application requires intermittent or continuous monitoring. Dewpoint’s online systems are available across dewpoint ranges between approximately -120°C and +20°C, with equivalent measurement units available depending on the system configuration.
Online Measurement for Continuous Visibility
Continuous monitoring can be particularly useful when moisture conditions need to be observed throughout an operating process. Instead of relying exclusively on periodic inspections, an online system can provide real-time information that operators can monitor from a local display or integrate with wider control equipment.
Dew-Point’s online range combines moisture sensing technology with different display and transmitter configurations. Systems can be configured as stand-alone solutions or for simultaneous continuous monitoring at multiple locations, including options using MODBUS RTU communications.
This approach can help make moisture measurement part of an established process-monitoring strategy rather than treating it as an occasional maintenance activity.
Choosing the Right Sensing Technology
The sensing element has a major influence on the performance of a moisture measurement system. For low moisture levels, the sensor needs to provide appropriate sensitivity, response speed, repeatability, and stability.
Dew-Point uses ultra-high-capacitance aluminium oxide sensing technology across several of its trace moisture instruments. Its published sensor specifications cover a dewpoint range from approximately -110°C to +20°C and identify applications involving dry compressed air and process gases. The sensor technology is also available in configurations certified for hazardous environments.
For continuous applications, the AMT transmitter uses the same type of aluminium oxide sensing technology and provides a stated accuracy of ±2°C dewpoint. It is available across various measurement ranges from -120°C to +20°C and can provide 4–20 mA and, on the Modbus version, RS485 communications.
Sampling Conditions Can Influence Results
Reliable analysis depends not only on the instrument but also on the quality of the gas sample reaching the sensor. Pressure, flow, temperature, sample-line materials, and the location of the sampling point can all influence measurement conditions.
A dedicated sample system can help make these conditions more controlled. Dew-Point’s PSS portable sample system is designed to precondition pressurized gas samples for compatible handheld hygrometers. It includes an integrated pressure regulator and flow indicator and is intended for intermittent measurements and spot checks.
For permanently installed systems, optional sensor holders and sample cells can also help establish suitable sampling conditions. The AMT’s optional sensor holder/sample cell is designed to allow the transmitter to be removed for annual calibration without interrupting the process.
Portable Analysis for Maintenance and Spot Checks
Not every moisture measurement requirement calls for permanent installation. Technicians may need to compare different sampling points, investigate an unexpected reading, or verify the performance of a drying system during maintenance.
The SADPmini2 handheld hygrometer is designed for rapid spot checks of dewpoint or trace moisture in gases and compressed air. Its specifications include an ultra-high-capacitance aluminium oxide sensor, a rechargeable battery providing more than 150 hours of continuous use, and accuracy of ±2°C dewpoint within its specified range.
For pressurized samples, the PSS can be paired with compatible handheld instruments to regulate and condition the sample before measurement. This can make field testing more convenient while reducing the need for complicated temporary sampling arrangements.
Applications Across Industrial Gas Systems
Trace moisture measurement has applications across industries where gas quality and dryness are important. Natural gas and LNG systems can use continuous moisture monitoring to help address risks associated with water and freezing in pipelines and valves. Pharmaceutical manufacturing can require accurate moisture determination for applications such as blanketing gases, while power generation facilities may monitor moisture in gas systems used for equipment operation.
Welding gases are another application where moisture can be monitored continuously to help maintain specified shielding-gas conditions. Dew-Point also identifies applications across aerospace, breathing air, food and beverage, medical gases, specialty gases, HDPE, and injection moulding.
The appropriate measurement strategy will vary according to the gas, process conditions, required moisture limit, and consequences of excessive moisture.
Solutions for Hazardous Environments
Some industrial facilities require moisture measurement equipment to operate in potentially hazardous atmospheres. In these situations, instrumentation must have the appropriate certification for the intended area.
Dew-Point offers intrinsically safe options for these environments. The AMT-Ex transmitter is certified to ATEX and IECEx standards and provides continuous trace moisture measurement in process gases and compressed air. It offers a range extending from -120°C to +20°C dewpoint and is specified for pressures up to 350 bar.
Portable testing is also available for hazardous applications through the SADPmini2-Ex and other intrinsically safe instruments, allowing technicians to perform measurements where standard equipment may not be suitable.
Calibration and Measurement Confidence
Calibration is an important consideration whenever moisture readings are used for process control, maintenance, or quality decisions. Documented calibration provides a way to verify instrument performance and maintain confidence in measurements over time.
Dew-Point states that its moisture measurement solutions can be supplied with calibration certificates traceable to National and International Humidity Standards. The online range specifies accuracy of ±2°C dewpoint, while selected transmitters include AutoCal span correction to support field checks between laboratory calibrations.
A suitable calibration schedule should be established according to the instrument, application, operating conditions, and quality requirements of the facility.
Selecting the Right Measurement System
Choosing the appropriate moisture analysis solution starts with understanding the application. Engineers should consider the expected moisture range, gas composition, pressure, temperature, sampling location, required measurement units, communication requirements, and whether the installation is hazardous or non-hazardous.
Portable instruments can provide flexibility for maintenance teams, while online transmitters and displays are better suited to continuous process monitoring. In more demanding applications, dedicated sample systems or customized engineering solutions may also be appropriate. Dew-Point states that it designs customized trace moisture measurement solutions when an off-the-shelf product does not meet a specific application’s requirements.
Building a Reliable Moisture Monitoring Strategy
Effective moisture monitoring is not simply about selecting an instrument with the lowest possible measurement range. The sensor, analyzer, sampling arrangement, calibration process, and data connection all need to work together according to the requirements of the application.
A Trace Moisture Analyzer can provide valuable information for facilities that need to monitor very low levels of water vapor in gases or compressed air. With portable instruments, online systems, transmitters, sampling equipment, and customized solutions, Dew-Point offers different approaches for obtaining reliable moisture data and supporting better control of industrial gas systems.
