2408
i Indicator Engineering Manual
3.7
Custom Linearisation
The linearisation uses a 15 point straight line fit.
Figure 3-7 shows an example of a curve to be linearised and is used to illustrate the terminology used in the
parameter list
Figure 3-7: Linearisation Example
3.7.1
Example: To Linearise Input 1
Do This
This Is The Display You Should See
Additional Notes
3.7.2
Compensation for Sensor Non-Linearity’s
The custom linearisation feature can also be used to compensate for errors in the sensor or measurement system,
so that discontinuities in the curve can be calibrated out. Figure 3.8 shows an example of the type of discontinuity
which can occur in the linearisation of a temperature sensor.
Figure 3-8: Sensor Non-linearity’s
VAL.H
VAL.L
VAL.2
to
VAL.14
in L
in H
in 2
( to
14
)
Ignored data
points
Terminated
search
Displayed value
Electrical input
Notes:
1.
The linearisation block works on rising
inputs/rising outputs or rising
inputs/falling outputs. It is not suitable
for outputs which rise and fall on the
same curve.
2.
Input Lo/Output Lo and Input Hi/Output
Hi are entered first to define the low and
high points of the curve. It is not
necessary to define all 15 intermediate
points if the accuracy is not required.
Points not defined will be ignored and a
straight line fit will apply between the
last point defined and the Input
Hi/Output Hi point.
1.
Press
as many times as necessary to
access the
<
CUSt1
>
list header menu
2.
Press
to show
<
in L
>
3.
Press
or
to enter the low
electrical input value
Input 1 is set to +1.0 units
CUSt1
in L
1.0
4.
Press
to show
<
VAL.L
>
5.
Press
or
to enter the low
electrical input value
The display will read 2.0
corresponding to the low electrical
input (+1 unit)
VAL.L
2.0
6.
Repeat steps 2 to 5 for the high end and
then for all intermediate steps
Note:-
The values entered must be
continuously increasing or
decreasing
The calibration of the sensor uses the same
procedure as described above. Adjust the
output (displayed) value against the
corresponding input value to compensate for
any errors in the standard linearisation of the
sensor
Output Hi
eg 1000
o
C
Output Lo
eg 0
o
C
Output
2( to 14)
Input Hi
eg 1000
o
C
Input Lo
eg 0
o
C
Input
2( to 14)
Cal Point 6
Cal Point 5
Cal Point 4
Cal Point 3
Cal Point 2
Cal Point 1
Electrical input
Part Number HA027240 Issue 5.0 Feb 2015
33