K-Patents PR-33-AC - Manual (Page 31)

6 Configuration and calibration 25
© Copyright K-Patents 2014. All rights reserved.
4. Field calibration: Adjustment of the calculated concentration value CALC may be
required to compensate for some process conditions or to fit the measurement to
the laboratory results. The Field calibration procedure, section 6.2.2, determines
the appropriate adjustment to CALC. The adjusted concentration is called CONC. If
there is no adjustment, CALC and CONC are equal. Thus the chemical curve is kept
intact as a firm base for the calculation, the adjustment is merely additional terms.
5. Damping: See Section 6.1.1.
6. Output signal: The output signal is transmitted over the 4–20 mA current output or
through the Ethernet connection (see chapter 9).
6.2.1 The chemical curve
The chemical curve is a model of the refractive index behaviour of the process medium.
It is used in calculating the Brix value from the measured n
D
and TEMP. The curve is
defined by a set of 16 parameters (Table 6.1).
C
00
C
01
C
02
C
03
C
10
C
11
C
12
C
13
C
20
C
21
C
22
C
23
C
30
C
31
C
32
C
33
Table 6.1 The chemical curve parameters
The Sanitary OEM Refractometer is shipped with a chemical curve to show the temper-
ature compensated Brix value of the process medium. The set of parameters is given
by K-Patents and should not be altered, except in case of changing to another process
medium.
6.2.2 Field calibration
K-Patents provides a field calibration service that adapts the calibration to the factory
laboratory determinations based on the data supplied. This field calibration corrects
the instrument reading to show the same values as the laboratory measurements.
The field calibration procedure should be made under normal process conditions using
standard laboratory determinations of sample concentration.