Vaisala HMT370EX Series Intrinsically Safe Humidity & Temperature Transmitter


  • Intrinsically safe (Exi)
  • Interchangeable probes
  • Detachable probe module
  • Graphical LCD display and non-display model
  • Vaisala HUMICAP sensor
  • Compatible with Vaisala Insight PC software
  • Traceable calibration (certificate included)

Dpstar is a leading supplier of environmental measurement sensors for temperature, relative humidity, pressure, dew point, CO2, and other environmental condition monitoring for industrial process application and research. Since the ’90s, we earned a reputation as a trusted partner to our clients through our commitment and dedication. We are an authorized distributor and supplier of measuring sensors solutions from renowned manufacturers Vaisala. Vaisala is a global leader in environmental and industrial measurement. Building on 80 years of experience, Vaisala provides observations for a better world. Vaisala is a reliable partner for customers around the world, offering a comprehensive range of innovative observation and measurement products and services.

The intrinsically safe HMT370EX is the ideal solution for use in hazardous areas up to zone 0 and 20. In addition to measuring relative humidity and temperature, the transmitter outputs also other humidity parameters: 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. 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. View the current certificates for the HMT370EX:

Dimensions in millimeters & (inches)

The HMT370EX offers several probe options for different applications:

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

Models for measuring moisture in oil and jet fuel:

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

Key Benefits

Intrinsically safe

The entire HMT370EX transmitter can be installed directly in explosive areas. It can withstand continuous exposure to potentially explosive environments that contain flammable liquids, gases or dust. Operation in any of these environments requires no additional protective enclosures.

Detachable probes

Probes can be easily replaced and removed for calibration outside the hazardous area without removing the entire transmitter. Attaching new probes involves minimal reconfiguration, as up-to-date settings can be restored from the transmitter.

Easy to configure

Output configuration and measurement calibration and adjustment can be carried out directly on the optional local display interface. Alternatively, you can connect the transmitter to Vaisala Insight PC software and configure both the transmitter and the probe together or separately.



This next-generation HMT370EX transmitter replaces the long-running HMT360 transmitter series.
Please note that the HMT370EX has been released with IECEx and ATEX certificates for intrinsically safe compliance, but FM and  CSA approval are still pending.


Measurement Performance
Relative Humidity
Measurement range 0 … 100 %RH
Accuracy at +23 °C (+73.4 °F) 1) ±0.8 %RH (0 … 90 %RH)
Factory calibration uncertainty 2) ±0.5 %RH (0 … 40 %RH)
±0.8 %RH (40 … 95 %RH)
T63 response time 15 s
Sensor options HUMICAP R2
Measurement range −70 … +180 °C (−94 … +356 °F)
Accuracy at +23 °C (+73.4 °F) 1) ±0.1 °C (±0.18 °F)
Factory calibration uncertainty 2) ±0.1 °C (±0.18 °F) at +23 °C (+73.4 °F)
Sensor Pt1000 RTD Class F0.1 IEC 60751
Other available measurement parameters 3)
Dew point temperature, wet-bulb temperature, absolute humidity, mixing ratio, water concentration, water mass fraction, water vapor pressure, and enthalpy
1) Defined against calibration reference. Including non-linearity, hysteresis, and repeatability.
2) Defined as ±2 standard deviation limits. Small variations possible; see calibration certificate.
3) For specifications, see HMT370EX User Guide
Operating Environment
Operating temperature for electronics -40 … +60 °C (-40 … +140 °F)
Operating temperature with display -20 … +60 °C (-4 … +140 °F)
Storage temperature -40 … +70 °C (-40 … +158 °F)
Pressure range See probe specifications
EMC compatibility EN 61326 1, industrial environment
Compliance marks RCM, CE, China RoHS
Inputs and Outputs
Operating voltage 12 … 28 V
Analog outputs 2 outputs (two-wire, 4 … 20 mA) Connection via safety barriers
Typical accuracy of analog outputs at +20 °C ±0.0625 % full scale
Typical temperature dependence of analog outputs 0.005 % / °C (0.005 % / °F) full scale
Service port connection USB cable 219690
Display options Graphical LCD display
Model without display
Mechanical Specifications
Connections Screw terminals, 0.33 … 2.0 mm2 wires (AWG 14-22)
Cable glands M20 x 1.5
Conduit fitting NPT 1/2″ and M16
Housing material EN AW-6082
Housing weight LCD transmitter: 1500 g (3.3 lb)
LED transmitter: 1520 g (3.35 lb)
HMP371 fixed probe: 320 g (0.7 lb)
IP rating IP66 (NEMA4)


Vaisala HMT370EX Series Intrinsically Safe Humidity & Temperature Transmitter_DpstarGroup