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Calibration Procedure
Introduction 7
7-3
Introduction
5026A-x sensors used with the thermo-hygrometer should be periodically calibrated 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 Fluke Authorized Service Center for return
instructions prior to returning 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.
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)
• 5020A Thermo-Hygrometer to use to read the 5026A-x sensor
• An extension cable to connect with the 5026A-x sensor placed inside the
temperature/humidity chamber
Preparation
Allow the 5026A-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 5026A-x
sensor inside the temperature/humidity chamber, near the center, attached to an extension
cable that runs to the 5020A outside the chamber. Place the PRT inside the chamber with
the tip close to the tip of the 5026A-x sensor. Run the probe cable to the outside of the
chamber and connect it to the PRT readout.
Calibration Points
Each measurement parameter, both temperature and relative humidity, is calibrated at
three points throughout its range with the other parameter held constant at the center of
its range. The following tables list the calibration points for the two sensor models and
for both measurement parameters.
Table 7-1. 5026A-S Temperature Calibration Points
Temperature At Relative Humidity
15 °C 45%
25 °C 45%
35 °C 45%
Table 7-2. 5026A-S Relative Humidity Calibration Points
Relative Humidity at Temperature