K-Patents PR-03 - Manual (Page 50)

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44 PR-03 instruction manual
Warning! Never try to change bias in a day-to-day manner, or week-to-week. Frequent bias changes will
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increase the measurement variation, not decrease it.
Amplification adjustment: The size of CONC% changes is directly proportional to the calibration constant
Gain. The point, where TEST = 128, is not influenced by Gain. From two measurement points the new
Gain can be estimated by the formula
New Gain = Old Gain * (LAB%1 - LAB%2) / (CONC%1 - CONC%2).
After the change of the Gain, the Bias has to be determined by a new sample.
The constants Square and Cube are linearity corrections that can be provided by K-Patents, see Sec-
tion 5.10.6.
5.10.3 Output current range selection
It is possible to change the concentration range of the output current even after the instrument is installed
and operating. The change is made through the display
Calibrate/Parameters/Output signals/Current output
.
Example: To change 4–20 mA = 15–25 CONC% to 4–20 mA = 10–30 CONC%, key in the sequence
Calibrate / Parameters / Output signals / Current output
and then enter Zero = 10 and Span = 20.
5.10.4 Temperature calibration
Normally the process liquid temperature is considerably higher than the ambient. Then the heat loss through
the refractometer sensor may cause the temperature display to be somewhat lower than the process temper-
ature. This will not impair the measurement, and the difference can be ignored.
If, however, the temperature has to show an absolutely correct value, then a bias in ◦ C can be added to the
temperature reading by giving the following key sequence
Calibrate/Parameters/Temperature/Temp bias
and entering the bias in degrees centigrade.
Note: A change of Temperature bias will cause a small change in the concentration output, due to the
temperature compensation. If necessary, this change can be compensated with a Bias change (see Sec-
tion 5.10.2).
5.10.5 Adjusting damping time
The damping time is the time it takes for the concentration measurement to reach half of its final value at
a step change of the concentration. For example, if concentration changes from 50 % to 60 % and damping
time is 10 s, it takes 10 seconds for the IT-R to show concentration 55 %. Figure 5.14 below shows how the
damping time affects the measurement curve.
The damping time is set in seconds with the key sequence
Calibrate/Parameters/Conc
(R.I.)/Damping time . A damping time of 5–15 seconds
seems to work best in most cases, the factory setting is 5 sec.
Warning! Avoid overdamping, the signal should not be made insensitive.
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