HygroMet4 - HM4

The HygroMet4 is suitable for use wherever high humidity prevails for short or long periods. In such environments condensation could occur on conventional probes, thereby delivering incorrect values. This is particularly the case in meteorology, in cheese cellars, tunnels and caves.

Heating Function
The HygroMet4 is equipped with an automatic sensor heater. It heats the sensor above ambient temperature by 0.1...10 °C depending on the settings. Heating of the sensor prevents the formation of condensation.
The following heating cycles can be selected and are freely programmable:

- Permanent heating
The sensor is constantly heated.

- Interval
The heater can be switched on hourly, daily, weekly or monthly at a definable point in time. The heating period can be set at will.

- Depending on current measured values
The sensor heater can be programmed such that it is only switched on if a certain humidity or temperature value is not reached or is exceeded.

Sensor cleaning
The programmable cleaning function heats the sensor to up to 150 °C. The cleaning function can be switched on daily, weekly or monthly at a definable point in time. The cleaning period can also be set.


  • Allows simultaneous measurement and heating
  • Measures relative humidity and temperature
  • Calculates off all psychrometric parameters
  • Freely programmable RoHumiHeat sensor heating
  • Adjustable RoHumiClean sensor cleaning
  • SMD Thermo sensor element
  • Outstanding accuracy and repeatability
  • Integrated real-time clock
  • Freely scalable analog output signals
  • RS-485 interface


  • Meteorological
Accuracy at 23 ±5 °C Heated: ±1.5 %rh
Probe type Meteorological probe
Operating range -40…85 °C / 0…100 %rh
Power consumption 15...24 VDC /
5...24 VDC (only 0...1 V) With heater: <55 mA @ VDD = 5 VDC / <30 mA @ VDD = 24 VDC Without heater: <35 mA @ VDD = 5 VDC / <20 mA @ VDD = 24 VDC
Long-term stability <1 %rh / year
Heating mode Permanent heating / Interval / Depending on current measured value
Heating period 1...255 min.
Heating element SMD Thermo
Humidity sensor SMD Thermo
Temperature sensor PT100 1/3 DIN Class B
Response time t 63 <25 sec.
Allowed wind speed 20 m/s, with filter
Communication interfaces RS-485
IP protection rating IP65

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