Calibration of humidity instruments - HMK15

HMK15 User Guide

Document code
M210185EN
Revision
E
Language
English (United States)
Product
HMK15
Document type
User guide

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 spotlights, 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 lids and rubber plugs are carefully closed.
Figure 1. Salt chamber
1
Humidity probe
2
O-rings
3
Sensors
4
Max. depth 10 mm (0.39 in)
5
Thermometer
6
Saturated salt solution
7
Undissolved salt