YSI 600DW-B Sonde - Manual (Page 294)

Frequently Asked Questions About YSI Drinking Water Systems Appendix H
TESTING OF PROTOTYPE YS DW SYSTEM RUNNING CONTINUOUSLY ON A 6500 IN WATER
WITH AN AVERAGE pH OF 8.7; RECALIBRATION OF SENSOR AFTER 20 DAYS
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
0 10 20 30 40 50 60 70
TIME, DAYS
FREE CL2,
M
G
/L
QC
YSI
SENSOR CALIBRATION
Is there any difference in the calibration of Drinking Water sonde sensors from standard YSI sondes
for surface- or ground-water?
Only for the free chlorine sensor. Sensors other than free chlorine (typically conductivity, pH, ORP, and
turbidity) are calibrated in the same way in drinking water sondes as for standard YSI 6-series surface- and
ground-water sondes, using the same calibration vessels. As described in the next section, however, the
calibration of the free chlorine sensor is somewhat different.
How is the Free Chlorine Sensor Calibrated?
To calibrate the free chlorine sensor, you must make an independent measurement of the free chlorine in
the flow cell effluent at the time of calibration. This is usually done by collecting a effluent sample,
adding a chemical to it (DPD) which will form a red color which is proportional to the free chlorine in the
sample and then determining the intensity of the color using a commercial colorimeter. The analysis is
very simple and takes only about 2 minutes to perform. Once the true chlorine value has been determined
from the DPD colorimetric analysis, this value is input into the sonde software and the calibration is
confirmed.
Where can I obtain the chemicals and colorimeters which are necessary to calibrate the YSI free
chlorine sensor?
The YSI 9000 and 9100 Photometers and the version of the Hach Pocket Colorimeter
TM
II which is
specific for free and total chlorine are examples of colorimeters which can be purchased for the analysis of
free chlorine in water samples. In addition, you usually will need to purchase the color-forming reagents
in either pill or powder form – YSI Item # YAP 001 for the YSI photometers; Hach Item # 21055-69 for
the Hach colorimeter. The cost of the reagents is nominal.
YSI Incorporated Drinking Water Monitoring Systems Operations Manual H-8