9
Calibration Procedure
2626-x sensors used with the thermo-hygrometer should be periodically cali-
brated to ensure accuracy. A six-month calibration interval for the first year,
and one-year thereafter, is recommended. The thermo-hygrometer display unit
does not require calibration, and the sensor can be sent to a qualified service
center for calibration without the thermo-hygrometer display unit. Contact a
Hart Scientific Authorized Service Center for return instructions prior to return-
ing the probe for calibration. Ensure that the probe is packaged adequately to
ensure safe transport. It is recommended that you acquire and use the optional
probe case for transport.
For those who wish to perform their own calibration, the calibration procedure
is outlined as follows.
9.1
Equipment
•
Temperature/humidity chamber to use as a relative humidity reference and
a stable-temperature environment (0.37% RH uncertainty or better is
recommended)
•
PRT and associated readout to use as the reference thermometer (0.03°C
uncertainty or better is recommended)
•
1620 Thermo-Hygrometer to use to read the 2626-x sensor
•
An extension cable to connect with the 2626-x sensor placed inside the
temperature/humidity chamber
9.2
Preparation
Allow the 2626-x sensor to “dry out” in air with relative humidity between 20
and 50% and temperature between 16 and 30°C for 24 hours before calibration.
Place the 2626-x sensor inside the temperature/humidity chamber, near the cen-
ter, attached to an extension cable that runs to the 1620 outside the chamber.
Place the PRT inside the chamber with the tip close to the tip of the 2626-x sen-
sor. Run the probe cable to the outside of the chamber and connect it to the
PRT readout.
9.3
Calibration Points
Each measurement parameter, both temperature and relative humidity, is cali-
brated at three points throughout its range with the other parameter held con-
stant at the center of its range. The following tables list the calibration points
for the two sensor models and for both measurement parameters.
1620 the “DewK”
139
9 Calibration Procedure
