Calibrating The Concentration Measurement - Vaisala K-PATENTS PR-23 Series Instruction Manual

6 Configuration and calibration
NAMUR NE 43 uses the 3.8 to 20.5 mA signal range for measurement information,
with ≥21 mA or ≤3.6 mA to indicate diagnostic failures (see Figure 6.11). With that
information, it is easier to detect a failure condition on a refractometer, for example,
it clearly tells you whether you have an empty pipe or a failed instrument.
failure
0 3.6 4
3.8
Figure 6.11 Default mA output values
– and
6 SEC DEFAULT MODE
for empty pipe (message
that cause the measurement to revert to default mA. By default the secondary mA
output is disabled.
– allows you to set different output values to check the output signal.
8 MANUAL SET
Press the key to return normal output function.
BACK
Note: If you want to 'turn off' the mA output, select

6.4 Calibrating the concentration measurement

The concentration calibration of
the PR-23 refractometer is or-
ganized in six layers.
1. The information from the CCD
element and the Pt-1000 tem-
perature element. The po-
sition of the shadow edge
(Figure 1.4, "Optical image
detection") is described by
a number called CCD and
scaled from 0–100 %.
2. The sensor calibration: The
actual refractive index n
calculated from the CCD value.
The process temperature is
calculated from the Pt-1000
resistance. The sensor out-
put is n and temperature
D
TEMP in Centigrade. Hence,
the calibrations of all PR-23 sensors are identical, which makes sensors inter-
changeable. Furthermore, the calibration of each sensor can be verified using stan-
dard refractive index liquids, see Chapter 13.
Measurement Data
OK
allow you to set a secondary mA output value
7 SEC DEFAULT
) to differentiate it from the other messages
NO SAMPLE
6. mA OUTPUT
DAMPING
5.
4. FIELD CALIBRATION
3. CHEMICAL CURVE
2.
is
D
1.
Figure 6.12 The six layers of
concentration calibration
failure
20 21
20.5
in the Source menu.
NOT DEFINED
CONC
CALC
Indicating
transmitter
DTR
Sensor
n
TEMP
D
CCD Pt-1000
51
mA