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Vaisala HMT370EX ATEX RH&T Transmitters

Vaisala HMT370EX is an intrinsically safe RH&T transmitter for use in hazardous areas up to zone 0 and 20. The primary measurement of Vaisala HMT370EX is relative humidity and temperature, however other humidity variables are available including: dew point temperature, wet-bulb temperature, absolute humidity, mixing ratio, water concentration, water mass fraction, water vapor pressure, and enthalpy. Special models for moisture in oil and jet fuel measurements are available, please contact Fluidic for help with product selection.  Like its predecessor, the HMT370EX offers a number of probe options.  Probes are connected securely and simply using a unique locking wheel feature. Again, Fluidic have trained and experienced engineers able to help you select the right probe option for your application.

Vaisala HMT370EX is released early 2021 to replace the Vaisala HMT360 EExia RH&T Transmitters.  These offer a straight in/out replacement and the same barriers/ isolators can be used (contact Fluidic for ATEX isolator options).  There is also a low cost adapter plate option to utilise existing HMT360 bracketry for upgrade installs.

Typical applications include fuel storage tanks, manufacturing of chemicals, pharmaceuticals and food, biogas production’ paint booths and any other industry or process where intrinsically safe humidity or moisture in oil measurement is required.


Vaisala HMT370EX probe options:

  • HMP371 – for wall mounting
  • HMP373 – for confined spaces
  • HMP374 – for pressurized spaces
  • HMP375 – for high temperature
  • HMP377 – for high humidity
  • HMP378 – for pressurized pipelines

Plus models for measuring moisture in oil and jet fuel:

  • HMP378F – for moisture in oil
  • HMP378H – for JET A-1 fuel


Vaisala HMT370EX Specifications

  • Intrinsically safe ATEX II 1 G Ex ia IIC T4 Ga (Gas) and II 1 D Ex ia IIIC T200 85 °C Da (Dust)
    • IECEx qualifications also available
  • 2 wire, loop powered design.  4-20mA
  • Interchangeable probes with detachable probe module
  • Graphical LCD display and non-display model
  • Environmental conditions -40 … +60 °C
  • Proven Vaisala HUMICAP® sensor technology for long term stability
  • Compatible with Vaisala Insight PC software
  • Machined, aluminium housing with anodized surface (EN AW-6082), IP66
  • The transmitter body is mounted directly on the wall and no extra bracket required.
    • If you are replacing an HMT360 instrument, there is a mounting plate to utilise your existing bracket.
  • Traceable calibration from the factory as standard (certificate included)
  • Extended measurement outputs with selections from RH&T (primary), dew point temperature, wet-bulb temperature, absolute humidity, mixing ratio, water concentration, water mass fraction, water vapor pressure, enthalpy


Output configuration and measurement calibration and adjustment can be carried out directly on the local display interface. For additional configuration and monitoring options, you can connect the transmitter to Vaisala Insight PC software with an accessory USB cable (part number 219690).  The probe and transmitter body can be connected to Insight for configuration either together as one unit or separately.


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 HMT370EX datasheet
  • Download Vaisala HMT370EX Installation & Safety Guide
  • Download Vaisala HMT370EX ATEX Cert
  • Download Vaisala Application Note on Intrinsically Safe Installs
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