Errors during humidity calibration are commonly due to temperature differences. A temperature difference of ±1 °C at +20 °C (+68 °F) between the air in the chamber and the sensor causes an error of ±3 %RH at 50 %RH and an error of ±6 %RH at 97 %RH. The length of the stabilization time depends on how great the difference is between the transportation or process temperature and the calibration site temperature. In laboratory use, the calibrator should be stored where the room temperature is most stable. The calibrator must be kept out of direct sunlight and away from localized heat sources, such as spot lights, heaters, and soldering irons. If the probe or transmitter is checked against several humidity references, the checking must first be made at the dry end. For more information, see the respective transmitter or probe user guide at www.vaisala.com.
Handle the probe as little as possible. Do not hold the salt chamber or other parts of the calibrator in your hand during calibration as they warm up and cause errors in the readings.
|Even the smallest water drop on the probe near the sensor distorts the readings. Make sure that the chamber covers and rubber plugs are carefully closed.|