7.4.3 Field calibration
Vaisala provides a field calibration service that adapts the calibration to the factory
laboratory determinations based on the data supplied. The field calibration procedure
should be made under normal process conditions using standard laboratory determinations
of sample concentration.
Record the calibrating data on the field calibration form found in Field calibration form
(page 261), also available by emailing a request to helpdesk@vaisala.com. Email the
completed field calibration form to your local Vaisala representative. Vaisala makes a
computer analysis of the data and sends optimal calibration parameters 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 40 (page 76).
• 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 number, the
sensor serial number and the sensor position, meaning whether it is installed as Sensor A or
as Sensor B.
Accurate calibration is only achieved if the sample is taken correctly. Pay special attention to
following details:
• The sampling valve and the refractometer should be installed close to each other in the
process.
Wear protective clothing appropriate to your process when
operating the sampling valve and handling the sample.
WARNING!
• Run the sample before starting to collect data points to avoid sampling old process
liquid that has remained in the sampling valve.
Chapter 7 – Configuration and calibration
75
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