Relative humidity: Using electrical instruments with hygroscopic sensors (NT BUILD 475)

  • Report #: NT BUILD 475
  • Approved: November 1996
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This test method is used for the determination of the relative humidity of ambient air by means of electric instruments with hygroscopic sensors. If the air temperature is also measured, the absolute moisture content can be determined.


Instruments with hygroscopic sensors are used for measurement of the relative humidity of ambient air, e.g. in dwellings, offices, laboratories and factories. They can also be used for measurement in confined spaces, such as drillholes in a concrete slab. The method can also be used for determination of the relative humidity of air in equilibrium with the pores of specimens of building materials stored in a closed air volume. Most instruments have an additional sensor for measurement of the air temperature. Readings of the temperature are necessary if the absolute moisture content is to be calculated. Some instruments have outputs for continuous recording.

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