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5.5 TDS Calibration Notes
1.
A Zero calibration should be performed at least monthly. In low TDS applications (where a
zero error is particularly significant), a zero calibration may have to be done weekly.
2.
A Standard calibration should be performed at least weekly. Of course, more frequent
calibration will result in greater confidence in results.
3.
Conductivity and TDS calibration data is stored separately in memory. Ensure that the
90-FL
has been correctly calibrated for the mode in which it will be used. The
90-FL
does not
require re-calibration when alternating between Conductivity and TDS modes, providing the
instrument has been correctly calibrated for each mode on the k factor sensor to be used.
4.
All calibration information is retained in memory when the
90-FL
is switched off. This
information can be recalled or printed later using the GLP function (see section 8).
5.
The
90-FL
displays the value of the standard to which it will attempt to calibrate. Ensure that
the standard value displayed corresponds to the standard that you are using. Alter the Standards
set-up if necessary (see section 5.2).
6.
Calibration settings for k=0.1, k=1 and k=10 sensors are NOT stored separately.
The
90-FL
requires re-calibration when a new k factor sensor is connected.
5.6 TDS Calibration Messages
1.
If a Zero Calibration has been successfully performed, the
90-FL
will display the following
message…
0.00ppM 25.0
o
c
Calibration OK, Zero=0.01ppM
2.
If a Standard Calibration has been successfully performed, the
90-FL
will display the following
message and the calculated k factor of the sensor. For example…
36.00ppK 25.0
o
c
Calibration OK, k=9.90
3.
If a Standard Calibration has failed, the
90-FL
will display the following message and the
calculated k factor of the sensor. For example…
Calibrate Failure. Check STD=36.00ppK
k=15.0, Exceeds Limit
Notes
2.
The allowable k factor range is +/-25% of nominal. This range is ample to allow for correctly
functioning TDS sensors. If calibration fails due to the k factor being outside these limits, then
please consult the Troubleshooting guide (section 16.3) for possible remedies.