Analog Output Overrange Behavior
Analog outputs of the GMW80 series transmitters have a defined behavior when
the values measured by the transmitter are outside the scaled analog output
range.
n At the top end of the output range, the output is clipped to the maximum value
of the output. This means that even if the measured parameter rises, the
value does not change anymore.
n At the low end of the output range, the output stays at the minimum value
when the measured parameter falls below the scaled range.
n The output is eventually set to the error state if the measured parameter is far
enough from the scaled output range. The exact limits for this behavior are
parameter dependent;see the figures below.
For more information on the error state, see Error State on page33.
20.0
0
0 2000 6000
Output clipping limit
Error level
CO
2
(ppm)
-100
Output
(mA)
Scaled output range:
4 ... 20 mA
0 ... 2000 ppm
3.6
4.0
Figure 7 Overrange Behavior of CO
2
Measurement with 4...20mA Output
Negative ppm values cannot physically exist but the behavior of the output is
defined to account for cases where a low CO
2
reading, combined with sensor
drift, could cause a negative result.
13
2 Product Overview
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