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6.4 Ratio Calibration Notes
1. The two Conductivity sensors MUST be calibrated in separate containers, as they interfere with
each other.
2. The
smart
CHEM
-C
checks that the sensors have the same k factor, and that a suitable k factor
is being used for the conductivity level of the solutions being measured whenever Ratio mode
is selected and before every Ratio calibration. The following table details the acceptable limits
of Conductivity for k=0.1, k=1.0 and k=10 sensors. All of these sensors will work to zero
Conductivity, but accuracy below the recommended minimum Conductivities listed will be
diminished.
Sensor k Factor
Recommended
Minimum Conductivity
Maximum Limit of
Conductivity
k=0.1
0.1 uS/cm
10 mS/cm
k=1.0
1 uS/cm
100 mS/cm
k=10
10 uS/cm
1000 mS/cm
3. A Ratio calibration should be performed at least weekly. Of course, more frequent calibration
will result in greater confidence in results.
7. Conductivity, TDS, Resistivity and Ratio calibration data is stored separately in memory.
Ensure that the
smart
CHEM
-C
has been correctly calibrated for the mode in which it will be
used. The
smart
CHEM
-C
does not require re-calibration when alternating between modes,
providing the instrument has been correctly calibrated for each mode on the k factor sensor to
be used.
8. All calibration information is retained in memory when the
smart
CHEM
-C
is switched off.
This information can be recalled or printed later using the GLP function (see section 10).
9. For Ratio mode, only one calibration setting is stored. If the k factor of the sensors is changed,
this mode must be re-calibrated.
6.5 Ratio Calibration Messages
1. If a Ratio Calibration has been successfully performed, the
smart
CHEM
-C
will display the
following message…
Calibrate OK
Delta Span = 1.010
2. If a Ratio Calibration has failed, the
smart
CHEM
-C
will display the following message and
the calculated difference between the outputs of the sensors. For example…
Calibrate Failed.
Delta GAIN = 150.0%
Check Cells, Ensure
Identical Standards
Notes
1. The allowable difference in k factor between the two sensors is 50% to 200%. This range is
ample to allow for correctly functioning Conductivity sensors. If calibration fails due to the k
factor being outside these limits, then please consult the Troubleshooting guide (section 18.3)
for possible remedies.