PCC-IV Instruction Manual (Rev. 0.1)
Page 6-39
Section 6
– Blockware Functions
Technical Reference
Deadband or Hysteresis (Parameter 2): When Deadband (DB)=
0.0: Output = 1, if PV > SP; or 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.
Internal vs External Setpoint (Parameters 1 and 3, and Input 2):
By default, Parameter 1 = 2, and
HIALM
uses the INTERNAL
SETPOINT stored in Parameter 3 as the SP. Changing
Parameter 1 to "1", causes
HIALM
to use the EXT SP (External
Setpoint) Input (Input 2) as the SP.
In EXT SP mode: A
FPCON
(F55) Input to EXT SP allows the
Operator to adjust an alarm setpoint from the front panel
Process mode display channels, and
FPCON
's Min/Max
parameters can limit the range of adjustment. If the
PID
setpoint
FPCON
Block feeds a
WSUM
(F52) Block, and
WSUM
connects
to the EXT SP, the
HIALM
setpoint can be a constant
percentage above the Operator adjusted
PID
setpoint.
Alarm Time Delay (Parameter 5): PV must be continuously greater than SP for (Parameter 5) seconds before the
HIALM
Block Output will change to a "1". See bottom figure at right.
Alarm Disable (Parameter 4, and Input 3): By default,
HIALM
is Enabled and responds to alarms because the
defaults are: Input 3 is Block 2 (
D0
or Low), and Alarm Disable is ACTIVE HI (Parameter 4 = 1). However, Blockware
can use the Disable Input (Input 3) to selectively Disable individual alarm Blocks, that is force the alarm Block Output
to be a "0". Parameter 4 determines if the Disable signal is "Active HI", or "Active LO" as follows:
Parameter 4
Disable Input
Mode
1 (Active HI)
0
Enabled
1 (Active HI)
1
Disabled
0 (Active LO)
0
Disabled
0 (Active LO)
1
Enabled
---------------------------------------------------------------------------------------------
NAME: HIALM SINGLE USE FUNCTION: N OUTPUT TYPE: D
---------------------------------------------------------------------------------------------
Input Type Description Notes
_____________________________________________________________________________________________
1 A PV INPUT
2 A EXT SP INPUT (Optional) 1
3 D DISABLE INPUT 2
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 % INTERNAL SETPOINT 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" above.
2. See "Alarm Disable" above.
3. See "Deadband" above.
4. See "Alarm Time Delay" above.
0
20
40
60
80
100
0
5
10
15
P
e
rc
e
n
t
Seconds
HIALM: SP=50, DB=10, DELAY=4
