CLX-Ex (10/11) Page 19
REV 1.5
7.2 Zero (offset) Calibration Procedure
Generally this calibration is only required if readings are expected to be below 1 mg/L or if
it is required by a regulatory authority. To perform this calibration, the water supply to the
CLX-Ex must be changed to chlorine free water such as de-ionized water. This chlorine free
water must be run through the instrument for at least 5 minutes prior to using the following
procedure.
1. On the CLX-Ex, press the MODE/EXIT
button once. The screen is shown to the right.
2. Press either the or buttons to get the
screen shown to the right.
3. Press to enter the zero calibration screen.
4. The screen will show the current reading on the CLX-Ex. Since there is no
chlorine, the only reading may be a slight offset due to the absorbance of the
reagents. There should be no pink color developed.
5. Press to perform a Zero calibration. When the calibration has completed the
instrument will return to AUTO measurement mode automatically.
There is a limit of ±0.20 mg/L total adjustment available. A ZERO Cal. greater than
this will cause a CAL warning and no calibration will have occurred. Enter SERVICE
mode to clear this error.
7.3 Restore Factory Settings
If the CLX-Ex displays a CAL error or the calibration was incorrectly performed, it may be
desired to restore the factory calibration. All factory defaults including factory
configurations can be reset by holding down the button and then pressing and releasing
the button then releasing the button.