Practical advice for measuring humidity

The most common source of error when measuring relative humidity is a difference between the temperature of the probe and the temperature of the environment. At a humidity condition of 50 % RH, a temperature difference of 1 °C (1.8 °F) typically results in an error of 3 % RH on relative humidity.  astm a1008

It is good practice to monitor the display of the moisture meter for temperature stability. The probe should be given sufficient time to come to equilibrium with the environment to be measured. The larger the initial temperature difference between the probe and the environment, the more time is required for temperature equilibrium.

In extreme situations, condensation may occur on the sensors when the probe is colder than the environment. As long as the humidity / temperature limits of the humidity sensor are not exceeded, condensation does not alter the calibration of the sensor. However, the sensor has to dry out before it can provide a valid measurement.

  • Step 1: Check the correct functionality of the instrument and probe using the humidity standard tube.
  • Step 2: Concrete floor slab and air space surroundings must be at service temperature / humidity for at least 48 hours.
  • Step 3: Define numbers of test holes
  • Step 4: Define depth of test holes
  • Step 5: Drill and prepare test holes
  • Step 6: Wait 72 hours for moisture equilibrium
  • Step 7: Measure

o Insert in-situ probe into sleeve

o Wait for temperature equilibrium

o Check for stable values

  • Step 8: Report all necessary information