Seacom supplies moisture measurement instruments for transformer oil, lubrication oil, hydraulic fluid, paper, cardboard, compressed air, dry process gases and vaporised hydrogen peroxide applications.
Moisture is measured differently in each material. Oil applications commonly use water activity or relative saturation, dry gases are usually assessed by dew point, and paper or cardboard can be screened using a material-specific capacitance meter. Selecting the correct measurement principle is therefore as important as selecting the measurement range.
Moisture Measurement Solutions Available
Online moisture-in-oil probes: Continuously measure water activity, relative saturation, temperature and calculated water concentration in transformer, lubrication and hydraulic oils.
Fixed moisture-in-oil transmitters: Provide a compact permanently installed solution with analogue or digital outputs for monitoring and control.
Portable moisture-in-oil measurement: Supports field spot checks, diagnostics, temporary logging and comparison of installed probes.
Paper and cardboard moisture meters: Provide rapid non-destructive screening of rolls, sheets, stacks, tissue, carton and corrugated board.
Moisture in compressed air and process gases: Uses dew-point measurement to determine dryness in air, nitrogen and compatible industrial gases.
Vaporised hydrogen peroxide measurement: Measures H2O2 vapour concentration and, according to the selected probe, humidity, saturation and temperature during bio-decontamination.
Indigo smart-probe transmitters: Add local display, analogue outputs, relays, Ethernet and other system-integration functions to compatible Vaisala probes.
Practical single-probe platform providing a local display and model-dependent analogue, relay or Modbus RTU outputs.
Understanding Moisture in Oil Measurements
Water activity (aw): Indicates how close the oil is to moisture saturation at its present temperature, from 0 for very dry oil towards 1 at saturation.
Relative saturation (%RS): Expresses the same saturation relationship as a percentage from 0 to 100%RS.
Water concentration (ppmw): Estimates the mass concentration of water and depends on the solubility characteristics of the specific oil.
Temperature: Must be evaluated together with moisture because the amount of water an oil can dissolve changes significantly with temperature.
Water activity and relative saturation directly indicate the risk of free-water formation. A ppm calculation is useful only when the correct oil-specific solubility coefficients are available and configured.
Information Required for Moisture Instrument Selection
Measured material: Identify the exact oil, fuel, gas, paper, cardboard or vapour being measured.
Required parameter: State whether the result is required as water activity, relative saturation, ppm, dew point, percentage moisture or H2O2 concentration.
Expected measurement range: Provide normal and maximum moisture levels together with the required temperature range.
Pressure and process conditions: Specify pressure, temperature, flow, contamination and whether the process can be isolated during installation.
Installation method: Confirm pipe or tank dimensions, process thread, insertion depth, ball-valve requirement and available service clearance.
Fixed or portable measurement: Choose continuous online monitoring, temporary logging, routine spot checks or laboratory screening.
Output and communication: Identify requirements for analogue output, Modbus RTU, Ethernet, Modbus TCP, relays or local display.
Oil-specific ppm calculation: Provide the oil brand and type so the availability of suitable solubility coefficients can be checked.
Calibration: State the required certificate, calibration points, tolerance and recalibration interval.
Common Industrial Moisture Applications
Power transformers: Monitor dissolved moisture and the changing risk of free-water formation in insulating oil.
Lubrication systems: Detect water ingress before it affects lubricant performance, bearings and rotating machinery.
Hydraulic equipment: Track moisture that can contribute to corrosion, fluid degradation and component damage.
Oil dryers and purifiers: Trend inlet and outlet moisture and control treatment cycles according to actual oil condition.
Compressed air and process gases: Verify gas dryness using dew-point measurement under the actual operating pressure.
Paper and packaging: Screen moisture variation in rolls, sheets, cartons and corrugated board during production, storage and incoming inspection.
Bio-decontamination: Monitor vaporised hydrogen peroxide concentration and process humidity during chamber or room decontamination cycles.
Need Help Selecting a Moisture Instrument?
Contact Seacom with the measured material, required moisture parameter, expected range, temperature, pressure, process connection, output signal and calibration requirements. Our team can recommend a suitable moisture-in-oil probe, transmitter, portable meter, dew-point instrument or paper moisture meter.
Vaisala HUMICAP® MMT310 Series provides continuous online measurement of moisture and temperature in transformer, lubrication and hydraulic oils.
The compact transmitter measures water activity (aw) or relative saturation (%RS), showing how close the oil is to forming free water. Optional ppm calculation is available for mineral transformer oil and configured oil types.
Models MMT317 and MMT318
Water activity range: 0 to 1 aw
Temperature range: -40 to +180°C
Two configurable analogue outputs and RS-232C
Up to 40 bar with MMT318 and ball-valve installation
The Vaisala MMT330 Series provided continuous measurement of moisture and temperature in transformer oil, lubrication oil, hydraulic fluid and other liquid hydrocarbons.
Discontinued series; not recommended for new installations
Legacy MMT332, MMT337 and MMT338 probe configurations
Measures water activity, relative saturation, temperature and calculated ppm
Graphical display, data logging and versatile analogue or digital outputs
Used for oil-condition monitoring, dryer control and free-water risk detection
The Vaisala DM70 was a portable meter for dew-point spot checks, process measurements and data logging. It is discontinued and replaced for general dew-point work by the Vaisala Indigo80 handheld indicator with a DMP80A or DMP80B probe.
Legacy DMP74A, DMP74B and SF₆-specific DMP74C probe options
Direct or sampled measurement in pressurised processes
Portable numerical and graphical display with data logging
Current replacement: Indigo80 with DMP80A or DMP80B
DMP80A for moderate dew points down to −40 °C Td/f
The Vaisala MMP8 provides continuous online measurement of dissolved moisture and temperature in transformer oil, lubrication oil, hydraulic fluid and other liquid hydrocarbons.
Measures water activity from 0 to 1 aw, relative saturation, temperature and ppmw
Dry-end accuracy up to ±0.01 aw or ±1%RS
Temperature measurement from −40 to +180 °C
Available in standard 262 mm and long 448 mm probe versions
Adjustable insertion depth with ISO 1/2 or NPT 1/2 process fittings
Standalone Modbus RTU or connection to Vaisala Indigo transmitters
The Vaisala Indigo200 Series is the standard transmitter platform for one interchangeable Indigo-compatible smart probe, providing local display and practical automation-system connectivity.
Indigo201 with three analog outputs and two relays
Indigo202 with Modbus RTU and two relays
Colour display with numerical and graphical views
IP65 enclosure for industrial measurement applications
The Vaisala Indigo500 Series provides flagship industrial measurement integration: choose Indigo510 for a simplified single-probe system or Indigo520 for full dual-probe capability.
Indigo510: one probe and two isolated analog outputs
Indigo520: two probes, four isolated outputs and two relays
Ethernet web interface and Modbus TCP communication
The Vaisala Indigo300 is a rugged industrial transmitter for one Vaisala Indigo-compatible smart probe, providing local measurement display and up to three configurable analog outputs.
Its corrosion-resistant IP66 metal enclosure, flexible probe mounting and interchangeable probe design make Indigo300 suitable for humidity, temperature, dew point, CO2, moisture in oil and other demanding industrial measurements.
The Vaisala DPT145 provides online dew-point, pressure and temperature measurement for SF6-insulated electrical equipment. The model is being discontinued and should not be specified for new projects.
Measures dew point, pressure and temperature
Calculates SF6 density, normalised pressure and moisture in ppm
RS-485 communication with Modbus RTU
Contact Seacom for availability and replacement assessment
This website uses cookies to ensure you get the best experience on our website
