Xylem FDO 925/STM, Руководство по эксплуатации, Страница: 6 / 11

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Measuring 2.3
Minimum depth of
immersion
Observe the required minimum immersion depth
(

chapter „Technical Data“).
Incident flow The FDO
®
925 D.O. sensor enables precise measurements without any
incident flow.
However, an incident flow of the sensor membrane improves the responding
behavior of the sensor (

chapter „Technical Data“).The incident flow can
be provided in different ways, e. g.:

The flow of the water to be measured is sufficient (aeration tank, water
pipe, stream)

Slowly pull the sensor through the water by hand (lake, container), or

Use a flow aid such as a magnetic stirrer with stirring device.
Function check and user calibration 2.4
Factory calibration The FDO
®
925/STM is factory calibrated. In the recommended application
(

chapter 1.2), the measuring characteristics of the sensor cap remain
stable for the specified service life. Thus, a use
r
calibration is not usually
required.
When does a check
or user calibration
make sense?
A function check or user calibration can be useful in the following special
cases:

If the measured values appear to be implausible and it is assumed
that the service life of the sensor cap is over.

Routinely within the framework of the company quality assurance.
Check- or
calibration medium
The check and user calibration take place in water vapor-saturated air. The
suitable conditions are easily provided with the aid of the check and
calibration vessel, FDO
®
Check. For this purpose, moisten the sponge inside
the vessel. Then insert the sensor in the vessel as far as it will go. The
sensor membrane must be clean and dry for this.
1 2
Moisten the sponge:

Remove the cap (1).

Take out the sponge (2), wet it, then slightly squeeze it out.

Insert the sponge again and close the calibration and storage vessel
with the lid.
After inserting the sensor, wait for the temperatures of the sensor and
calibration vessel to adjust.
The steps of the check or user calibration are described in detail in the
operating manual of the meter.