Vaisala K-PATENTS PR-43, Руководство пользователя

Страница: 32 / 54

Layer 1: The refractometer calibration : The actual refractive index n
D
is calculated from the
CCD.
Layer 2: The chemical curve : The refractometer calculates the Brix or concentration value
based on n
D
and TEMP. The result is a temperature compensated calculated concentration
value CALC.
Layer3: Field calibration : Adjustment of the calculated concentration value CALC may be
required in order to compensate for some process conditions or to fit the measurement to the
laboratory results. The field calibration procedure determines the appropriate adjustment to
CALC. The adjusted concentration is called CONC.
Output signal: The output signal is transmitted over the 4–20 mA current output or through
the Ethernet connection.
6.2.1 Chemical curve
The chemical curve is the theoretical concentration curve based on n
D
and TEMP. It is defined
by a set of 16 parameters.
A chemical curve is specific to the given process medium, for example sucrose or sodium
hydroxide. The set of parameters is given by Vaisala and should not be altered, except in case
of changing to another process medium.
6.2.2 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 PR-43 refractometer field calibration form (page 46) , also
available by emailing a request to helpdesk@vaisala.com . Email the completed field calibration
form to either helpdesk@vaisala.com or your local Vaisala K-PATENTS® representative. A
computer analysis of the data is made at Vaisala and optimal calibration parameters are sent
to you to be entered in the system.
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 .
• LAB%: Sample concentration determined by the user
• 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 refractometer serial number.
Accurate calibration is only achieved if the sample is taken correctly. Pay special attention to
following details:
PR-43 Series User Guide M212455EN-B
30