West Control Solutions KS98-1 - Manual (Page 146)

III-8 Limit value signalling and limiting
III-8.1 ALLP ( alarm and limiting with fixed limits(No. 40))
Signal limiting:
Parameter L1 determines the minimum, H1 the maximum 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 -
vided by calculation cycle time Tr (100, 200, 400, 800ms).
Thus input variable x1 can be monitored for its rate of change.
9499-040-82711 Limit value signalling and limiting
ALLP ( alarm and limiting with fixed limits(No. 40)) III-146
Select
H1 H2
L2
L1
x1 Y1
h1
h2
l1
l2
Xsd
x0
_
H2
L1
H1
Fig. 9 Limiting at H1 < L1