2 calibrating the concentration measurement – K-Patents PR-33-S User Manual

Page 27

5 Conﬁguration and calibration

5.2 Calibrating the concentration measurement

ETHERNET

FIELD CALIBRATION

CHEMICAL CURVE

CCD

TEMP

Pt-1000

CONC

CALC

DAMPING

Figure 5.2

The layers of concentration

calibration

The concentration calibration of the

K-Patents inline refractometer PR-33

is organized in six layers.

1. The information from the CCD

element and the Pt-1000 tem-

perature element. The position

of the shadow edge (Figure 1.4,

“Optical image detection”) is de-

scribed by a number called CCD

and scaled from 0-100 %.

2. The sensor calibration: The ac-

tual refractive index n

is calcu-

lated from the CCD value. The

process temperature is calcu-

lated from the Pt-1000 resis-

tance. The sensor output is n

and temperature TEMP in Centi-

grade.

Hence, the calibrations

of all PR-33 sensors are identi-

cal, which makes sensors inter-

changeable.

Furthermore, the

calibration of each sensor can be

veriﬁed using standard refractive

index liquids.

3. The chemical curve: The sensor calculates the concentration value based on n

and

TEMP according to chemical curves derived from available chemical literature and

K-Patents expertise. The result is a temperature compensated calculated concen-

tration 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. The Field calibration procedure determines the appropriate