6 Conguraon and calibraon
51
6.4.3 Field calibraon
K-Patents provides a ield calibration service that adapts the calibration to the factory
laboratory determinations based on the data supplied. The ield calibration proce-
dure should be made under normal process conditions using standard laboratory de-
terminations of sample concentration.
Record the calibrating data on the PR-23 ield calibration form (found in the end of
this manual), also available at <http://www.kpatents.com/> and by emailing a request
to <info@kpatents.com>. Fax the completed Field calibration form to either K-Patents
headquarters or your local K-Patents representative. A computer analysis of the data
will be made at K-Patents and optimal calibration parameters will be sent to be en-
tered in the Indicating transmitter DTR.
For a complete report, 10–15 valid data points (see below) are needed. A data point is
of use for calibration only when the diagnostic message is NORMAL OPERATION. If prism
wash is employed, do not take samples during the wash. Each data point consists of:
LAB% Sample concentration determined by the user
From DTR display: (see Figure 6.13)
CALC Calculated concentration value
T Process temperature measurement in Centigrade
nD Actual refractive index n
D
CONC Measurement in concentration units, the large size number
In addition to the calibration data, write down the Indicating transmitter serial num-
ber, the sensor serial number and the sensor position, i.e. whether it is installed as
Sensor A or as Sensor B.
Accurate calibration is only achieved if the sample is taken correctly. Pay special at-
tention to following details:
− The sampling valve and the refractometer should be installed close to each other
in the process.
Warning! Wear protective clothing appropriate to your process when operating the
sampling valve and handling the sample.
− Run the sample before starting to collect data points to avoid sampling old process
liquid that has remained in the sampling valve.
− Read the values CALC, T(emp), nD and CONC in the DTR’s display at exactly the same
time with sampling.
The easiest way of doing this is to use the FIELD SAMPLE soft key available through
the Sensor status display (DTR program version 2.0 or newer). The value of each
sample is the average of 10 consequent measurements to increase accuracy and
reduce possible process noise.
− Use a tight container for the sample to avoid evaporation.
Important: Ofline calibration using process liquid very seldom gives reliable results,
as problems are caused by
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