Vaisala HMP8 Relative Humidity & Temperature Probe


  • RH accuracy up to 0.8 %RH.
  • Temperature accuracy up to 0.1 °C (0.18 °F).
  • Temperature measurement range -70 … +180 °C (-94 … +356 °F).
  • Sensor purge provides superior chemical resistance.
  • Probe installation depth can be freely adjusted and probe can be hot-swapped from pressurized pipelines with an installation valve.
  • Modbus RTU over RS-485.
  • Plug & play compatible with Indigo™ series of transmitters.
  • Traceable calibration certificate: 5 points for humidity, 1 point for temperature.

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 Vaisala Temperature Probe HMP8 and Vaisala HUMICAP Humidity are made for pressurized settings like compressed air systems and refrigerant dryers. They’re easy to insert and remove from pipelines and can be adjusted to fit different depths. The HMP8 belongs to the Indigo product line and works with Indigo500 and Indigo200 series transmitters, as well as the free Insight PC Software.


Key Benefits

Proven Vaisala HUMICAP performance

Vaisala is the original innovator of the thin-film capacitive humidity measurement technology, which has now become the industry standard in humidity measurement.

Chemical purge minimizes effects of contaminants

In environments with high concentrations of chemicals and cleaning agents, the chemical purge option helps to maintain measurement accuracy between calibration intervals.

Flexible connectivity

The probe is plug and play compatible with Vaisala Indigo series transmitters, can be used as a standalone digital Modbus RTU transmitter, or connected to Vaisala Insight™ PC Software.


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 Pt100 RTD Class F0.1 IEC 60751
Operating Environment
Operating temperature of probe body −40 … +80 °C (−40 … +176 °F)
Operating temperature of probe head −70 … +180 °C (−94 … +356 °F)
Operational pressure < 40 bar
Measurement environment For air, nitrogen, hydrogen, argon, helium, oxygen, and vacuum 1)
IP rating of probe body IP66
1) Consult Vaisala if other chemicals are present. Consider safety regulations with flammable gases
Inputs & Outputs
Operating voltage 15 … 30 V DC
Current consumption 10 mA typical, 500 mA max
Digital output RS-485, non-isolated
Protocols Modbus RTU
Output Parameters
Absolute humidity (g/m3) Relative humidity (%RH)
Absolute humidity at NTP (g/m3) Relative humidity (dew/frost) (%RH)
Dew point temperature (°C) Temperature (°C)
Dew/frost point temperature (°C) Water concentration (ppmv)
Dew/frost point temperature at 1 atm (°C) Water concentration (wet basis) (vol %)
Dew point temperature at 1 atm (°C) Water mass fraction (ppmw)
Dew point temperature difference (°C) Water vapor pressure (hPa)
Enthalpy (kJ/kg) Water vapor saturation pressure (hPa)
Mixing ratio (g/kg) Wet-bulb temperature (°C)
EU directives EMC Directive (2014/30/EU)
RoHS Directive (2011/65/EU)
EMC compatibility EN 61326 1, industrial environment
Type approvals DNV GL certificate no. TAA00002YT
Compliance marks CE, China RoHS, RCM, WEEE
Mechanical Specifications
Connector M12 5-pin A-coded male
Probe fitting ISO1/2” and NPT1/2” fittings included
Weight Weight
Probe AISI 316L
Probe body AISI 316L
Cable jacket FEP
Ball valve ISO 1/2″ with welding joint BALLVALVE-1
Indigo USB adapter 1) USB2
1) Vaisala Insight software for Windows available at


Vaisala HMP8 Relative Humidity & Temperature Probe_DpstarGroup