Analytical Technology Unit 1 & 2 Gatehead business PK, OL3 5DE
Phone +44 145 783 2800
Fax +44 145 783 9500
[email protected]
Q45H Training Handout 4.05
Page 4 of 11
Chlorine Span Cal
“1 Ref”
Span calibration of the system must be done against known value of chlorine in the sample ‘at the point in which you
are calibrating the unit and no longer than a couple of minutes to prevent an alteration in the process that could lead
to an incorrect cal’. A sample should be collected from the inlet line feeding the flow cell and quickly analyzed for
free chlorine. The chlorine monitor should be calibrated while operating on a chlorinated sample stream in the flow
cell assembly.
IS YOUR SAMPLE WATER > 8 PH AND VARIABLE OF +/- 0.2 (i.e. 8.3 today and 8.5 tomorrow) PLEASE
CONTACT ATI FOR ASSISTANCE WITH CONFIGURATION OF THE INTERNAL CURVE CORRECTION!
ATi uses a DPD colorimetric method to measure the free chlorine. Calibrate system as follows:
1.
Once the sensor has been in the flow cell long enough for polarization (8 hours on a new sensor, 15-20 minutes
on an already ‘polarized’ sensor) you can begin the calibration. If the sensor is on-line the user may want to set
the output HOLD feature prior to calibration to lock out any output fluctuations.
2.
Scroll to the CAL menu section using the MENU key and press ENTER or the UP arrow key.
Cal Cl
2
will then be
displayed.
3.
Press the ENTER key. The screen will display a flashing
1-Ref
for span calibration or a
2-Zer
for zero
calibration. Using the UP arrow key, set for a
1-Ref
span calibration and press ENTER. AT THIS POINT CARRY
OUT THE DPD TEST AND WAIT FOR AT LEAST 20 SECONDS PER DPD TABLET AND CARRY OUT 2 TO 3 TO GET
THE CORRECT AVERAGE!
4.
The system now begins acquiring data for the calibration value. As data is gathered, the units for ppm and
temperature may flash. Flashing units indicate that this parameter is unstable. The calibration data point
acquisition will stop only when the data remains stable for a pre-determined amount of time. This can be
overridden by pressing ENTER twice. If the data remains unstable for 10 minutes, the calibration will fail and the
message
Cal
Unstable
will be displayed.
5.
The screen will display the last measured ppm value and a message will be displayed prompting the user for the
DPD value. The user must then modify the screen value with the arrow keys and press ENTER. The system then
performs the proper checks.
6.
If accepted, the screen will display the message
PASS
with the new sensor slope reading, and then it will return
to the main measurement display. If the calibration fails, a message indicating the cause of the failure will be
displayed and the FAIL icon will be turned on. The range of acceptable values for sensor slope is 20% to 600%.
It may be necessary to rebuild the sensor as described on page 2, Chlorine Sensor Assembly. Should the slope
value remain out of range and result in calibration failures, review the Service Section of this manual, then
contact the service dept. at ATI for further assistance.
The sensor offset value in % from the last span calibration is displayed on the lower line of the Default Menus for
information purposes. Once the % goes to <25% THE NEXT TIME YOU CAL CHANGE MEMBRANE &
ELECTROLYTE AS THE SLOPE IS AT ITS MINIMUM BEFORE FAILING.
