Vaisala K-PATENTS PR-23 Series, Instruction Manual, Page: 63 / 246

6 Configuration and calibration 53
6.4.3 Field calibration
Vaisala provides a field calibration service that adapts the calibration to the factory lab-
oratory determinations based on the data supplied. The field calibration procedure
should be made under normal process conditions using standard laboratory determi-
nations of sample concentration.
Record the calibrating data on the PR-23 field calibration form (found in the end of this
manual), also available by emailing a request to
<info@kpatents.com> . Fax or email
the completed Field calibration form to your local Vaisala KPATENTS
®
representa-
tive. A computer analysis of the data will be made at Vaisala and optimal calibration
parameters will be sent to be entered 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: Offline calibration using process liquid very seldom gives reliable results,
as problems are caused by