Programming
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permanently in the unit. It means that a pre-adjusted transmitter can be operated directly
with the indicator without any need to previously connect the signal to be measured to the
indicator.
The indicator can be scaled freely according to the physical dimension to be measured.
6.2.2.
Sensor calibration
If, on the other hand, the sensor has not been pre-calibrated, the indicator can be adjusted
and calibrated direct via the measurement together with the sensor path. This can be
selected via the parameter PN0 = 0 and is consequently called
sensor calibration
.
6.2.3.
Sensor linearisation
In addition, non-linear sensors can be linearised with the aid of a characteristic line that can
be saved in the indicator. This is described with the following example: The sensor signal
must be parameterised in a
strictly monotonously manner
, i.e. every new calibration
point (e.g. PN104) must have a higher input signal than the previous one (e.g. PN103) so
that it is taken over by the indicator. Otherwise, no confirmation will be shown. On the other
hand, the relevant indication values do not need to increase constantly. They can also fall
or alternate between rising and falling.
Example:
To program e.g. 5 additional calibration points, 5 must be entered under PN100.
Subsequently, for each of the calibration points, the voltage/current must be applied to
the unit and the respective indication value programmed under the following program
numbers PN101 – PN105.
Linearisation of a pressure transmitter (0 ... 100 mbar) with output 0 … 20 mA.
The indicated value before correction can be either calculated from the known
characteristic line of the transmitter or determined empirically. The non-linear range is
between 0 ... 75 mbar. For calibration point 101, this means:
A pressure of 15 mbar, the transmitter delivers 3.3 mbar instead of the ideal value of
3.0 mbar. Since 20 mA in the display corresponds to 100.0 mbar, 3.3 mA in the
display corresponds to 16.5 mA before the correction.
Setpoint
(PN)
Pressure
[mbar]
Output
transmitter [mA]
Indication
before
correction
(IN)
Desired
indication
(OUT)
2 0
0.5 2.5 0.0
101 15
3.3
16.5
15.0
102 30
6.2
31.0
30.0
103 40
9.2
46.0
40.0
104 60 11.4
57.0
60.0
105 75 14.7
73.5
75.0
1 100 20.0 100.0 100.0
