YSI 600DW-B, Руководство пользователя

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Frequently Asked Questions About YSI Drinking Water Systems Appendix H
YSI Incorporated Drinking Water Monitoring Systems Operations Manual H-7
Can I just make up a free chlorine standard from commercial bleach and use that to calibrate my free chlorine
sensor?
This procedure is not recommended and is likely to result in significant errors in your subsequent readings for three
reasons: (1) The concentration of hypochlorite on the bleach bottle is for new bleach batches and may not be correct if
the bleach has been on the shelf for varying periods of time; (2) Dilute solutions of hypochlorite may be unstable and
change during the calibration procedure; and (3) Because the free chlorine sensor is flow dependent, it needs to be
calibrated in water flowing at the same rate as will be used in the continuous monitoring studies. This flow condition is
almost impossible to meet by immersing the sensors in stagnant or agitated solutions of bleach. It is important to
understand that YSI may not be able to provide customer support for users who do not perform their free chlorine
sensor calibrations by the recommended procedure.
Could I measure total chlorine with my colorimeter kit and then calibrate the YSI Free Chlorine sensor to that
value?
Subject to additional field trials as described above, you might be able to do this if you know that there is a high
percentage of combined chlorine in your water and you are willing to accept qualitative versus quantitative results in
terms of accuracy. Remember, however, that, even if the sensor does respond in some way to combined chlorine, you
would not really be measuring total or combined chlorine – only a qualitative value for the oxidation capability of the
water. In addition, it is likely that you would see calibration errors when using the total chlorine value. Overall, it
should be remembered that the YSI sensor is designed to measure
free chlorine, and, until additional research is
performed, any attempts to correlate the sensor output with other parameters is risky.
What accuracy does free chlorine sensor provide?
Immediately after calibration at any value, the sensor should show an accuracy of +/- 15 % of the reading or 0.05 mg/L,
whichever is greater, over the specified range of the sensor (0-3 mg/L). Subsequent inaccuracy will be determined by
the drift of the sensor, the extent of which can vary with the water being monitored. It is important to remember that
the accuracy specification provided for the free chlorine sensor does not include long term drift even though our
empirical studies in several water monitoring sites show that the specification can be met in extended deployments as
shown in the figures below. Inaccuracy of the sensor from drift (determined from periodic colorimetric analysis) can
easily be removed by recalibration of the sensor at the time of quality checks.
Study 1