Vaisala HMP1 Humidity & Temperature Probe


  • Probe for wall mounting when combined with Indigo series transmitters.
  • RH accuracy up to ±1 %RH and temperature accuracy up to 0.2 °C (0.36 °F).
  • Temperature measurement range -40 … +60 °C (-40 … +140 °F).
  • Chemical purge provides superior chemical resistance.
  • Modbus RTU over RS-485 for flexible connectivity.
  • Includes a traceable calibration certificate: 6 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.

Vaisala HMP1 is made for indoor ambient measurement. It connects directly to Indigo200 series transmitters, creating a single wall-mounted unit. With its integrated probe head and body, it uses a miniature 5 mm HUMICAP sensor for stability and quick response. Vaisala HMP1 is part of the Indigo product family and compatible with Indigo200 and Indigo500 Series Transmitters. HMP1 can also be used with the Vaisala Insight PC Software for data visualization, easy probe configuration, and self-calibration.​


Key Benefits

Wall Mounting With Indigo Series Transmitters

Vaisala  HMP1 is part of the Vaisala Indigo family, so it can also be used with the Vaisala Indigo500 and Indigo200 transmitters to create a wall-mounted transmitter setup. The transmitters offer various additional benefits, such as display for data visualization and easy access to probe configuration, as well as more connectivity options, supply voltage choices, and wiring flexibility. Whether using Vaisala HMP1 standalone or with an Indigo transmitter, it can be connected to the Vaisala Insight PC software for easy field calibration, probe setup, and device analysis.

Fast response time and excellent measurement performance

The probe head and body of HMP1 are integrated into a single unit. Vaisala HMP1 uses the same miniature HUMICAP® sensor and probe head as Vaisala HMP9. This compact probe ensures fast response time and excellent measurement performance – even in rapidly changing environments.

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. The chemical purge involves heating the sensor to remove harmful chemicals. The function can be initiated manually or programmed to occur at set intervals.


Measurement Performance
Relative Humidity
Measurement range 0 … 100 %RH
Accuracy at +23 °C (+73.4 °F) 1) 2) ±1.0 %RH (0 … 90 %RH)
Factory calibration uncertainty 3) ±0.7 %RH (0 … 40 %RH)
±1 %RH (40 … 95 %RH)
Measurement range −40 … +60 °C (−40 … +140 °F)
Accuracy at +23 °C (+73.4 °F) 1) 2) ±0.2 °C (±0.36 °F)
Factory calibration uncertainty 3) ±0.1 °C (±0.18 °F) at +23 °C (+73.4 °F)
1) Defined against calibration reference. Including non-linearity, hysteresis, and repeatability.
2) In typical room conditions.
3) Defined as ±2 standard deviation limits. Small variations possible; see calibration certificate.
Operating Environment
Operating temperature −40 … +60 °C (−40 … +140 °F)
Storage temperature −40 … +60 °C (−40 … +140 °F)
Measurement environment For air, nitrogen, hydrogen, argon, helium, and oxygen 1)
IP rating IP50
1) Consult Vaisala if other chemicals are present. Consider safety regulations with flammable gases.
Inputs and Outputs
Operating voltage 15 … 30 V DC
Current consumption 2 mA typical, 200 mA max.
Digital output RS-485, non-isolated
Protocol 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
Compliance marks CE, China RoHS, RCM, WEEE
Mechanical specifications
Connector M12 5-pin A-coded male
Weight 38 g (1.34 oz)
Probe AISI 316L
Probe body PBT
Indigo USB adapter 1) USB2
1) Vaisala Insight software for Windows available at


Vaisala HMP1 Series Humidity & Temperature Probe_DpstarGroup