21
Chapter 4
Calibration and Maintenance
The Q-T
RAK
requires very little maintenance to keep it performing well.
The Q-T
RAK
may be calibrated in the field using the instructions below.
Even so, we recommend that you return your Q-T
RAK
to TSI for calibration
annually. For a reasonable fee, we will quickly clean and recalibrate the unit,
update software and firmware, and return it to you in “as new” working
condition along with a Certificate of Calibration and NIST Traceability. The
factory calibration is more precise than can be accomplished with the
procedures below. This “annual checkup” helps ensure that the Q-T
RAK
is
always in good operating condition.
Calibrating the CO
2
Concentration Measurement
TSI recommends calibrating the Q-T
RAK
CO
2
measurement monthly to help
ensure accurate readings. The CO
2
concentration measurement is affected by
changes in atmospheric pressure. Normal day-to-day variations due to local
weather conditions have little effect. However, changes in altitude can cause
more significant errors. For best accuracy, calibrate the Q-T
RAK
CO
2
measurement for your local conditions or if conditions change.
To calibrate the CO
2
sensor, please follow the procedure below. Brief
instructions can also be found on the calibration collar itself. You will need a
cylinder of pure air or nitrogen for the zero calibration and a cylinder of gas
with a known concentration of CO
2
for the span calibration. Contact your
local TSI distributor for available CO
2
calibration kits.
Note
: If using air for calibration, it must be specified to have less than
10 ppm CO
2
. Ambient room air cannot be used.
If necessary, you can select between the factory CO
2
calibration and a user
calibration. Please refer to Appendix B: “Internal DIP Switch Settings.”
The calibration procedure can be aborted at any time by pressing the
CO
2
,
TEMP,
or
HUMIDITY
key.
If an error occurs during the
CO
2
calibration procedure, the Q-T
RAK
displays the message
“ERR.”
Press the
CO
2
,
TEMP,
or
HUMIDITY
key to
abort the calibration. Switching the zero gas with the span gas is an example
of a condition that causes the
“ERR”
message to come on.
