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4.2 Measurement Notes:
1. When taking sample measurements, always ensure that there is
adequate flow of solution past the membrane for accurate, stable
readings. See section 21.6.
2. If salinity-corrected ppM Dissolved Oxygen readings are required, set
the salinity correction value before taking sample measurements. See
section 8.
3. If Altitude or Atmospheric Pressure Correction is selected, set the
correction value before calibrating and taking measurements. See
section 9.
4.3 Calibration Notes
1. A zero calibration should be performed at least monthly, or when the
membrane is replaced. In applications where there is a low level of
dissolved oxygen, a zero calibration may have to be done weekly.
2. An air calibration should be performed at least weekly, or when the
membrane is replaced. Of course, more frequent calibration will result
in greater confidence in results.
3. The salinity correction value is ignored during zero and air calibration.
There is therefore no need to re-set the salinity correction value when
calibrating Dissolved Oxygen.
4. For optimum accuracy, set the altitude of atmospheric pressure
before calibration.
5. All calibration information is retained in memory when the
WP-91
is
switched off, even when the battery is removed. This information can
be recalled or printed later using the GLP function (see section 10).