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Vaisala MMT330 Moisture in Oil Transmitter

Vaisala MMT330 are a series of moisture in oil transmitters for hydraulic and lubrication systems and transformer oil monitoring.  Unlike a “water cut” meter, Vaisala’s range of moisture in oil devices detect the unsaturated moisture in oil.  This offers improved condition monitoring of your oil, alerting problems before they occur.  Vaisala MMT330 is compliant with DNV GL 2.4 type approval (Class B) and also approved for installation in MAN Diesel & Turbo Two-Stroke Diesel Engines lubrication systems.


Efficient monitoring saves both oil and the environment. Vaisala MMT330 makes it simple and economical to monitor the changes of moisture in oil.   The instrument is compatible with Vaisala MM70 Handheld Moisture in Oil Meter for calibration.

There are three instruments in the types to enable various types of installations:

  • Vaisala MMT332 for high pressure installations
  • Vaisala MMT337 for tight spaces with a thread connection
  • Vaisala MMT338 for pipeline installations


As of 2021, Vaisala have introduced an Indigo series of transmitters that will eventually replace much of the 330 product family, including the MMT330 range.  Have a look HERE and please consult Fluidic for probe options.


Vaisala MMT330 features…
  • Continuous online measurement of moisture in oil
  • Installation through ball valve. No need to shut down the process.
  • Proven Vaisala HUMICAP® sensor, used for over 15 years in oil application
  • Easy field calibration and maintenance – compatible with Vaisala HUMICAP® Hand-Held Moisture Meter for Oil MM70
  • Online, real-time detection of moisture in oil without sampling.
  • Integrated data logging, with over four years of measurement history
  • Traceable calibration to national standards (certificate included)
  • Multi-year Calibration Care agreement option to ensure as-good-as new accuracy for years


Fluidic are a recognised partner of Vaisala CEN (Industrial division) for Scotland and the North of England. Our instrumentation engineers are product trained and able to help with instrument selection within the full range of Vaisala relative humidity and dewpoint transmitters.  Please call either office for more information (Glasgow 0141 641 5920,  Warrington 01925 572401).


  • Download Vaisala MMT330 Datasheet
  • Download Vaisala MMT330 User Guide
  • Download Moisture in Oil Application Note - Power Transformers
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