Calibration Services

If a sample of moist air is cooled, condensation will eventually occur at a temperature called the dew-point temperature. Knowing the dew-point temperature and the air temperature, the relative humidity of the air can be derived. It is not easy to determine relative humidity by direct measurement. However, dew-point temperature can be measured at high precision. Therefore, measurement of dew-point temperature provides an accurate method to determine relative humidity.

A dew-point generator is a facility capable of continuously supplying an air stream at accurately known dew-point temperature for instrument calibration and evaluation. Dew-point generators are usually based on the "two temperature" or "two pressure" principles.

Standards and Calibration Laboratory is able to provide calibration service for dew-point generators over the range from -60°C to 65°C. The generator is calibrated by measuring the dew-point temperature of its output air stream with a reference dew-point hygrometer.

 

In a dew-point hygrometer, air to be tested is drawn through a chamber containing a clean and highly polished mirror. A beam of light is directed on to the mirror and the reflected beam is monitored electronically in order to detect and control the formation of dew or frost.

To calibrate a dew-point hygrometer, a stream of low flow rate air, generated by a standard humidity generator and at the specified dew-point temperature, is passed through both the UUT and reference dew-point hygrometers which are then compared.