K-Patents PR-03 - Manual (Page 49)

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5 Startup, configuration and calibration adjustment 43
If the wash is not accepted, the diagnostic message will be Prism wash failure (see Section 9.7
for more information). This message is reset from the keyboard "Reset" or by a successful wash. A Wash
retries
parameter defines how many times wash is tried. The prism wash retries parameter is set with
Calibrate / Parameters / Prism wash / Wash check / Wash retries , the default
value (number of retries) is zero.
5.10 Adjusting concentration calibration
A K-Patents inline refractometer system is always delivered precalibrated according to the information given
by the user. The refractometer does not need any mechanical adjustments, all adjustments or changes of
range are made by keyboard entry only (Sections 5.10.2 and 5.10.3). The final calibration to obtain full
accuracy is made by collecting data from the actual process and sending that data to K-Patents or local
K-Patents representative for calculations and new calibration parameters (Section 5.10.6).
5.10.1 Checking current calibration
Wait until normal process conditions occur. The instrument is precalibrated at delivery, so a correct output
should be obtained automatically. If output is badly off-scale, check your process conditions.
If the diagnostic message is Normal operation but the concentration reading is not what could be
expected based on laboratory determinations, the deviation can be corrected with a calibration constant
bias
, see Section 5.10.2 below.
If the concentration reading is correct, but not the output mA, see Section 5.10.3 below for adjusting the
concentration reading.
The temperature by the refractometer sensor may not be exactly the same as the temperature given by a
separate process temperature sensor. Normally, a constant slight deviation in the temperature by the sensor
is not critical. However, it is possible to calibrate the sensor to give the exact process temperature, see
Section 5.10.4, “Temperature calibration”.
The damping of the concentration measurement may be increased if necessary e.g. to get a smoother
recorder track, see Section 5.10.5.
5.10.2 Concentration calibration from keyboard
The concentration display should be in agreement with laboratory determinations. If the diagnostic message
is Normal operation, deviations can be corrected from keyboard by adding a calibration constant
bias value . A change of the calibration constant bias influences the Conc% reading the same amount.
Key in Calibrate/Parameters/CONC (R.I.)/Parameters/Bias to read and change the Bias.
Example: If the CONC% display is 26% and the laboratory determination is LAB% = 28%, then a
value Bias = 23.456 should be changed to Bias + LAB% - CONC% = 25.456.
Note: The CONC% reading is restricted to positive values even if the mathematical calculation gives a
negative value. For a negative CONC% the display shows "0.0". For BIAS adjustment it is useful to know
the real CONC% value. For this reason the calculated negative CONC% reading is shown in the Calibrate
branch of the Selection tree, Figure 9.5.