Slope Process Calibration Procedure - Mettler Toledo thornton Bedienungsanleitung

pureO Dissolved Ozone Sensor
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Slope Process Calibration Procedure

Dissolved ozone sensor output will vary slightly over time
as the electrolyte, membrane and electrodes age. Periodic
calibration to a standard ozone measurement is needed at
intervals based on experience in the particular application.
Slope calibration is recommended every six months. The
calibration cycle may change based on application and
accuracy requirements. A slope calibration is performed by
comparison while measuring a stable ozonated sample.
Use the value of another reference ozone system using the
same water sample.
Colorimeter methods are typically used for ozone measure-
ment. Colorimeters have limited accuracy and are more
accurate at higher concentrations. It is recommended to
perform a slope calibration during sanitization when the
ozone concentration is > 200 ppb and stable. Slope cali-
bration must not be performed at locations where the ozone
has been removed by UV.
Because of the rapid decay of ozone in samples and the
limited repeatability of the ozone colorimetric method, it is
good practice to take at least three colorimeter measure-
ments to establish consistency and to take a fourth one if
a significant deviation is found between the first three. For
calibration, use the average of two measurements that are
consistent (e.g. within 10 ppb of each other).
Colorimeter samples must be taken from the same point
and measured very quickly to limit errors due to the rap-
id natural decay of ozone. Slope calibration will change
the stored slope value. For best accuracy, calibrate at the
normal operating sample temperature.
1. Before calibration, be sure that the instrument and
sensor have been powered for at least 12 hours.
They must also operate at least 12 hour in a sample
with more than 50 ppb of ozone. Please note that
for accurate calibration, the ozone level must be a
minimum of 200 ppb.
2. When ozonation is at steady state and a stable read-
ing is observed, obtain the value of reference dis-
solved ozone system taken from the on-line sensor
flow housing drain if possible.
3. Proceed through the instrument CALIBRATION menu
to perform a slope calibration.
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Printed in Switzerland Dissolved Ozone Sensor
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