Industrial gases and dry compressed air often need continuous moisture monitoring to maintain consistent process conditions and protect sensitive equipment. Unlike occasional field measurements, online monitoring provides a constant view of moisture levels as conditions change within a process. This can help operators identify unexpected increases in moisture and respond before they affect product quality, equipment performance, or system reliability. A suitable transmitter also needs to operate reliably under pressure and demanding industrial conditions while providing an output that can be integrated with existing control systems. Dew-Point offers moisture measurement technologies designed for continuous monitoring across a variety of industrial gas and compressed-air applications.
How Continuous Moisture Monitoring Supports Industrial Processes
Moisture conditions can change because of variations in gas supply, drying equipment, temperature, pressure, or process operation. Without continuous monitoring, these changes may remain unnoticed until they create a measurable problem. An online measurement system allows operators to observe moisture conditions as they develop rather than relying entirely on periodic inspections.
Dew-Point’s transmitter range is designed for continuous online trace moisture measurement in industrial gases and dry compressed air. The range includes general-purpose and intrinsically safe options, allowing users to select equipment according to their operating environment and measurement requirements.
The Role of a Dewpoint Transmitter in Process Monitoring
A dewpoint transmitter converts moisture measurements into an output signal that can be monitored by a display, PLC, SCADA system, or other process-control equipment. This makes it possible to incorporate moisture information into a wider industrial monitoring strategy.
The AMT model, for example, is a compact 2-wire, 4–20 mA loop-powered transmitter designed for continuous trace moisture measurement. It offers measurement ranges from -120°C to +20°C dewpoint, with stated accuracy of ±2°C dewpoint. The transmitter can also provide Modbus RTU communications over RS485 for digital process connectivity.
Sensing Technology for Trace Moisture Measurement
The sensing element is central to the performance of any moisture transmitter. Industrial applications may require measurements at extremely low moisture levels, so the sensor must provide appropriate sensitivity, repeatability, and stability.
The AMT uses ultra-high-capacitance aluminium oxide sensing technology. According to the manufacturer’s specifications, this technology is designed to provide sensitivity, response speed, accuracy, repeatability, and stability for trace moisture measurement. The transmitter can be configured to display moisture in units such as °C or °F dewpoint, ppm(V), ppb(V), g/m³, and lb/MMSCF.
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Connecting Moisture Data to Control Systems
One of the major advantages of online measurement is the ability to make moisture information part of an existing control or monitoring system. A suitable output can allow operators to view measurements remotely and respond to changes without physically visiting the sampling point.
The AMT provides a linear 4–20 mA output and is also available with Modbus RTU communication. Its digital communication capability can support integration with PLC and SCADA systems, while compatible Dew-Point displays provide options for local or remote viewing.
This type of integration can be useful where moisture levels form part of routine process monitoring. Instead of treating moisture testing as an isolated maintenance task, operators can include the measurement within their broader instrumentation strategy.
Choosing the Appropriate Measurement Range
Different processes operate at different moisture levels, so selecting the correct measurement range is an important part of specifying an instrument. A transmitter intended for very dry gases may require a substantially lower dewpoint range than equipment used for relatively wetter compressed-air applications.
The AMT is available in several configured ranges within an overall capability of -120°C to +20°C dewpoint. Dew-Point also offers the PDT transmitter for applications involving higher or “wetter” dewpoints, with ranges extending down to -60°C depending on the selected configuration.
Selecting the appropriate range can help ensure that the instrument is matched to the actual operating conditions instead of choosing equipment based only on its maximum or minimum specification.
Sampling Conditions Can Affect Measurement Quality
Even a high-quality transmitter needs an appropriate sampling arrangement. Pressure, flow, temperature, sample-point location, and the condition of the gas reaching the sensor can all influence the usefulness of the measurement.
Dew-Point offers an optional sensor holder and sample cell for its AMT transmitter. This arrangement is intended to provide suitable sampling conditions and can allow the transmitter to be removed for annual calibration without interrupting the process.
This can be particularly useful in industrial facilities where continuous operation is important and instrumentation maintenance needs to be planned without unnecessarily disrupting the process.
Applications Where Online Moisture Monitoring Matters
Continuous moisture measurement can support a wide variety of industrial applications. Natural gas and LNG systems may require moisture monitoring because water can contribute to freezing concerns in pipelines and valves. Food and beverage operations can monitor dry gases used during packaging, while pharmaceutical processes may require moisture control in blanketing gases.
Other applications include power generation, welding gases, medical gases, aerospace, HDPE production, and injection moulding. In each case, the reason for monitoring moisture can differ, but reliable online measurement provides operators with ongoing information about gas conditions.
Monitoring in High-Pressure Environments
Industrial gases may be transported or processed at significant pressures, making the mechanical construction of measurement equipment an important consideration. A transmitter needs to be suitable for the pressure and environmental conditions of the installation.
The AMT is designed for operating pressures up to 350 bar and uses a 316 stainless steel body with IP65/NEMA 4 protection. Its published specifications also identify a 316 stainless steel sensor protection filter and wetted probe materials.
These construction features can make the transmitter suitable for demanding industrial installations where both measurement performance and mechanical durability are important.
Options for Hazardous Areas
Not every transmitter is suitable for potentially hazardous environments. When flammable gases or explosive atmospheres may be present, the measurement equipment must have the appropriate certification for the installation.
For these applications, Dew-Point offers the AMT-Ex. It is an intrinsically safe transmitter certified to ATEX and IECEx standards and is designed for continuous trace moisture measurement in process gases and compressed air. The AMT-Ex also provides 4–20 mA output, uses aluminium oxide sensing technology, and can operate at pressures up to 350 bar.
The standard AMT is not certified for hazardous applications, so the appropriate model should always be selected according to the site’s safety requirements.
Calibration and Ongoing Measurement Confidence
Calibration is an important consideration when moisture measurements are used for process decisions or quality monitoring. A documented calibration process helps users verify that the instrument continues to perform within its specified accuracy.
The AMT is supplied with a calibration certificate traceable to National and International Humidity Standards at NPL. It also includes an AutoCal span-correction feature that allows field span checks and corrections between laboratory calibrations.
The AMT-Ex provides similar AutoCal functionality and is supplied with traceable calibration documentation, helping users maintain confidence in measurements in hazardous-area applications.
Selecting the Right Online Moisture Solution
Choosing a transmitter should begin with the application requirements. Engineers should consider the expected dewpoint range, gas type, operating pressure, temperature, required output, sampling arrangement, hazardous-area classification, and preferred measurement units.
A general-purpose transmitter may be appropriate for standard industrial environments, while an intrinsically safe model is required for applicable hazardous areas. Facilities may also need to determine whether a simple 4–20 mA connection is sufficient or whether digital communication such as Modbus RTU would provide greater integration flexibility.
Building a More Reliable Moisture Monitoring Strategy
Continuous moisture measurement can give industrial operators a clearer picture of changing gas conditions and help them identify problems earlier. When the transmitter, sensor, sampling arrangement, calibration process, and control-system connection are properly matched to the application, moisture data can become a useful part of routine process management.
Dew-Point provides transmitter options covering general industrial applications, higher-moisture conditions, and hazardous environments. With suitable sensing technology, multiple measurement ranges, flexible outputs, and calibration support, its solutions can help facilities maintain more consistent oversight of moisture in process gases and dry compressed air.