16 Limit value signalling and limiting
16.1 ALLP ( alarm and limiting with fixed limits )
Signal limiting:
Parameter L1 determines the minimum, H1 the maxi
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mum limiting. y1 is limited to the range between L1
and H1. (L1 ß y1 ß H1).
With parameter H1 smaller than L1, a higher priority is
allocated with H1. This means that y1 is ß H1.
Limit signaller:
The limit signaller has two 2 low and high alarms (L1, L2, H1 and H2). Configuration parameter Select can be used
to select the variable to be monitored (x1, dx1/dt, x1 - x0).
The limit values are freely adjustable as parameters and have an adjustable hysteresis of ? 0.
The smallest separation between a minimum and a maximum limit value is 0.
When an alarm is triggered, the corresponding output (L1, L2, H1 and H2) is logic “1".
D -alarm (dx1/dt)
Value x1(t-1) measured one sampling interval before is subtracted from instantaneous value x1(t). This difference is di
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vided by calculation cycle time Tr (100, 200, 400, 800ms).
Thus input variable x1 can be monitored for its rate of change.
Alarm with offset (x1-x0):
x1 can be shifted by means of x0. This corresponds to the offset of the adjusted alarm limits (L1, L2, H1 and H2) in par
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allel to the x-axis
.
9499 040 50611 Limit value signalling and limiting
97 ALLP ( alarm and limiting with fixed limits )
Limiting at H1
Offset of the alarm limits Switching hysteresis and alarm limits:
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