Humidity - Relative

Humidity is one of the most important measured parameters next to temperature. Humidity is water molecules in the air, and many chemical reactions, drying processes, meteorological conditions, and indoor comfort, are influenced by it.

We have to distinguish between absolute and relative air humidity.

Absolute humidity is the weight of the water content in the air, the water density. The unit of measurement is g/m3.

Relative Humidity represents the percentage of the maximum possible quantity of water vapour in the air with a referance to the temperature at the time of measurement. The unit of measurement is % RH.

There are various methods to measure relative humidity. Sigma`s sensors use the capacitive method.

Compact analogue transmitter for humidity and temperature

The compact analogue sensor is particularly suitable for stationary humidity measurement in heating and air conditioning ducts. The output signal 0 to 10 V corresponds to 0 to 100%RH. The humidity reading is temperature-compensated over the entire range.


  • Splash-proof plastic housing (IP54)
  • Easy and fast installation on the wall or in a duct with pipe clamp screws
  • For continuous high humidity applications, please select the heated version (see below)
  • Temperature output (Pt100) connected

Technical data

  • Meas. range 0 to+100 %RH
  • Accuracy ±2 %RH(+2 to+98 %RH)
  • Oper. temp. -20 to+70 °C
  • Storage temp. -40 to+80 °C
  • Accuracy/Humidity: at rated temperature of +25°C
  • Temperature compensation: 0.03%RH/°C
  • Output/Humidity: 0 to 10 V/0 to 1 V
  • Power supply: 18 to 28 V DC,
  • 1.6 m cable for clamping
  • A Pt100, DIN IEC 751, Cl. B in 4-wire version (connected), is available to measure temperature

Pipe clamp connection for wall mounting
Teflon sintered filter, Ø 21 mm, for corrosive substances, high flow velocities