PCC-IV Instruction Manual (Rev. 0.1)
Page 6-42
Section 6
– Blockware Functions
Technical Reference
F104 [RATE] Rate of Change Alarm
Function
RATE
calculates the % per second (%/sec) rate of
change of the Input signal every scan.
RATE
also saves the
%/sec values from the previous 5 scans in memory.
RATE
then computes the average %/sec rate of change over the
last 5 scans, and compares the average to the two alarm
thresholds in Parameters 1 and 2.
Alarm Time Delay (Parameter 4): If the average %/sec rate
exceeds either threshold continuously for more than
(Parameter 5) seconds, the
RATE
Output changes to a "1".
As soon as the average %/sec rate returns below both
thresholds, the
RATE
Output returns to a "0". See Figure.
Alarm Disable (Parameter 3, and Input 2): By default,
RATE
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 3 = 1). However, Blockware can use the
Disable Input (Input 2) to selectively Disable individual alarm Blocks; that is, force the alarm Block Output to be a
"0". Parameter 3 determines if the Disable signal is "Active HI", or "Active LO" as follows:
Parameter 3
Disable Input
Mode
1 (Active HI)
0
Enabled
1 (Active HI)
1
Disabled
0 (Active LO)
0
Disabled
0 (Active LO)
1
Enabled
---------------------------------------------------------------------------------------------
NAME: RATE SINGLE USE FUNCTION: N OUTPUT TYPE: D
---------------------------------------------------------------------------------------------
Input Type Description Notes
_____________________________________________________________________________________________
1 A INPUT
2 D DISABLE INPUT 1
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 + % /SEC LIMIT 10.0 100.0 0.1 1
2 - % /SEC LIMIT -10.0 -0.1 -100.0 1
3 ALARM DISABLE ACTIVE LO/HI
0=LO, 1=HI 1 1 0 2 1
4 ALARM DELAY SECONDS 0 600 0 1 2
Notes:
1. See "Alarm Disable" above.
2. See "Alarm Time Delay" above.
-10
-5
0
5
10
15
20
25
30
0
5
10
15
%/sec
, %
Input
Seconds
RATE, Limits: +2%/sec, -5%/sec
Input
%/Sec
Output
Output
