Vaisala HMP4 Relative Humidity & Temperature Probe



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  • HUMICAP R2 composite RH sensor
    • 0 to 100% RH range
    • Up to 0.8% RH accuracy
  • Pt100 RTD Class F0.1 IEC 60751 temperature sensor
    • -94 to +356°F (-70 to +180°C) range
    • Up to 0.18°F (0.1°C) accuracy
  • 15 to 30 VDC operating voltage
  • RS-485, non-isolated digital output
  • Modbus RTU protocol
  • M12/5 connector
  • IP66 rating
  • Connection cable required & sold separately

What's in the Box

  • M22x1.5 & NPT1/2 in fittings
  • Traceable calibration certificate

The Vaisala HMP4 relative humidity and temperature probe is designed for high-pressure applications, up to 100 bar, such as compressed air systems in maritime, breathing air, and industrial applications, where measurement performance and chemical tolerance are essential. The HMP4's IP66-rated housing makes it suitable for indoor or outdoor use.

With a HUMICAP R2 composite sensor, the HMP4 offers measurement ranges of 0 to 100% relative humidity and temperature from -94 to +356°F (-70 to 180°C). Vaisala's thin-film capacitive technology allows for RH accuracy up to 0.8% and the Pt100 RTD Class F0.1 IEC 60751 temperature sensor provides accuracy up to 0.18°F (0.1°C).

The Vaisala HMP4 is also part of the Indigo product family and compatible with Indigo 201 and 202 transmitters. The HMP4 is plug and play compatible with Vaisala's Indigo series of transmitters, or it can be used as a standalone digital Modbus RTU transmitter over RS-485 serial bus. If analog output is required the probe must be paired with an Indigo 201 transmitter.

Required Components

These additional components are required for the operation of your product. We strongly advise you to purchase these components unless you already own them or own a suitable alternative.

Vaisala Indigo 200 Series Remote Probe Cable
Replacement cable to connect remote probe to Indigo 201 & 202 transmitters


Please consider these optional accessories.

Vaisala Indigo 200 Series Transmitter
Plug-and-play connection for compatible CO2, vaporized hydrogen peroxide, humidity & temperature probes
Vaisala HM47280SP Sintered Filter
SS sintered filter 12mm diameter
Vaisala HM47453SP SS Filter Guard
SS filter guard for vacuum applications
Vaisala DRW010281SP PPS Grid
Vaisala DRW010281SP PPS Grid
Vaisala DRW010276SP Plastic PPS Grid Filter
Plastic PPS Grid Filter for HMP76/77
Vaisala 210696 Mounting Flange
Mounting flange for HMT330 Series Transmitters
Vaisala 242659 Connection Cable
USB cable used to connect Indigo probes to a PC for use with Insight software
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