Calibrating concentration measurement - PR-33 - PR-33-S

PR-33-S User Guide

Document code
IM-EN-PR33S
Revision
B
Language
English
Product
PR-33
PR-33-S
Document type
User guide

The concentration calibration of the in‑line refractometer PR-33 is organized in 6 layers.

Figure 1. Calibration layers
1
The information from the CCD element and the Pt- 1000 temperature element. The position of the shadow edge is described by a number called CCD and scaled from 0 to 100 %.
2
The refractometer calibration: The actual refractive index nD is calculated from the CCD value. The process temperature is calculated from the Pt‑1000 resistance. The refractometer output is nD and temperature TEMP in Centigrade.

The calibration process ensures same nD measurement performance for all PR‑33‑S refractometers, making them interchangeable. The calibration of each refractometer can be verified using standard refractive index liquids.

3
The chemical curve: The refractometer calculates the Brix value based on nD and TEMP. The result is a temperature compensated calculated concentration value CALC.
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.
5
Damping.
6
Output signal: The output signal is transmitted through the Ethernet connection.

The calibration of each refractometer can be verified using standard refractive index liquids.

Field calibration 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.

For more information on damping, see Signal damping.

By adding an optional mA output unit, the Ethernet signal can be converted into mA output.