Preferred Instruments PCC-IV, Instruction Manual

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PCC-IV Instruction Manual (Rev. 0.1) Page 6-40 Section 6
– Blockware Functions
Technical Reference
F102 [LOALM] Low Alarm
Function LOALM compares the PV (Process Variable) Input to
the SP (Setpoint) and changes the Block Output to a "1" when
PV < SP. If
LOALM is connected to a Panel Data Screen Tag,
or directly to an ROUT , DOUT , or TOUT Block, it can trigger
audible/visual alarms for the Operator. LOALM can also be
used as a trigger in Blockware to automate a control strategy.
See figure.
Deadband or Hysteresis (Parameter 2): When Deadband (DB)=
0.0: Output = 1, if PV < SP; Output = 0, if PV >= SP. When
Deadband > 0: Output = 1, if PV < SP; and once the Output
becomes a 1, it remains a 1 until PV > (SP + DB) and then it
resets to 0. See figure at right.
See
HIALM (F101) above for details on Inputs 2-3, and
Parameters 1, and 3-5.
---------------------------------------------------------------------------------------------
NAME: LOALM SINGLE USE FUNCTION: N OUTPUT TYPE: D
---------------------------------------------------------------------------------------------
Input Type Description Notes
_____________________________________________________________________________________________
1 A PV INPUT
2 A EXT SP INPUT 1
3 D DISABLE INPUT 1
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 SP MODE 1=EXT 2=INT 2 2 1 2 1
2 % DEADBAND 0.20 100.00 0.00 1 3
3 % INT SP 50.00 199.99 -199.99 1 1
4 ALARM DISABLE ACTIVE LO/HI
0=LO, 1=HI 1 1 0 2 2
5 ALARM DELAY SECONDS 0 600 0 1 4
Notes:
1. See "Internal vs External Setpoint" in HIALM (F101) above.
2. See "Alarm Disable" in HIALM (F101) above.
3. See "Deadband" above.
4. See "Alarm Time Delay" in HIALM (F101) above.
F103 [DEVALM] Deviation Alarm
Function DEVALM subtracts the PV (Process Variable) Input
from the SP (Setpoint) and changes the Block Output to a "1" if
the absolute value of the difference is greater than the allowable
Deviation (Parameter 2). Or, in equation form:
If |(PV-SP)| > Deviation Then Block Output = "1"
Note: "|(PV-SP)|
” means:
If (PV-SP) is negative, multiply by -1
If
DEVALM is connected to a Panel Data Screen Tag, or directly
to an ROUT , DOUT , or TOUT Block, it can trigger audible/visual
alarms for the Operator. DEVALM can also be used as a trigger
in Blockware to automate a control strategy.
Inputs 2-3, and Parameters 1, and 3-7 modify the basic behavior
as follows:
0
20
40
60
80
100
0 5 10
P
e
rc
e
n
t
Seconds
LOALM: SP=40, DB=10,DELAY=0
PV
SP
SP+DB
Output
0
20
40
60
80
100
0 5 10
P
e
rc
e
n
t
Figure xx Seconds
DEVALM: DEV SP=10, DB=5, Delay=0