Baelz Automatic 6490B - 3.7 Basic alarm type description

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Device manual 6490B / 6490B-y / 6590B
W. Bälz & Sohn GmbH & Co. Koepffstraße 5 D-74076 Heilbronn Telefon (07131) 1500-0 Telefax (07131) 1500-21
3.7 Basic alarm type description
The controller has got three basic types of alarms called type A, type B and type C.
3.7a Alarm type A
Alarm at a limit value based on the setpoint SP.
Alarm at over-temperature if alarm setting A1.A is
positive. Alarm at under-temperature if alarm setting
A1.A is negative. At positive setting the alarm is
triggered if PV is bigger than SP + A1.A . At
negative setting the alarm is triggered if PV is smaller
than SP -A1.A. The algebraic sign of the alarm
value A1.A only indicates the direction of effect
(over- or under-temperature).
The hysteresis defines a span between alarm state and
switching back to normal state. At positive setting of
A1.A returning to normal state is at
SP + A1.A - HY.1 . At negative setting of A1.A
returning to normal state is at SP - A1.A+ HY.1 .
Alarm type A
3.7b Alarm type B
Alarm at a fixed limit value of PV.
If AL.1 = 2, alarm is triggered if the value set at
A1.b is reached or exceeded.
The hysteresis defines a span between alarm state
and switching back to normal state. Returning to
normal state is at A1.b - HY.1 .
If AL.1 = 4, alarm is triggered if the value set at
A1.b is reached or dropped below.
The hysteresis defines a span between alarm state
and switching back to normal state. Returning to
normal state is at A1.b + HY.1 .
Alarm type B
3.7c Alarm type C
Alarm at leaving a band around the setpoint SP.
The lower half of the band is defined by A1.C ,
the higher one by A1.C. .
The value entered at A1.C is always negative
because the process variable PV has to be
smaller than SP -A1.C to trigger the alarm.
The value entered at A1.C. is always positive
because the process variable PV has to be
bigger than SP + A1.C. to trigger the alarm.
The hysteresis defines a span between alarm
state and switching back to normal state. For the
lower band returning to normal state is at
SP -A1.C+ HY.1 . For the higher band
returning to normal state is at
SP + A1.C. - HY.1. .
Alarm type C
At all three types (A, B, C) alarm is always triggered in case of sensor failure.