PCC-IV Instruction Manual (Rev. 0.1)
Page 6-23
Section 6
– Blockware Functions
Technical Reference
F56
[DEV] Deviation Calculation (for Bargraph Displays)
Function
DEV
subtracts the
two Inputs … Process Variable (PV) and Setpoint (SP) …, multiplies the difference by
a gain, and then adds a 50% bias to the result. When used with a Tag to control one of the front panel Bargraphs,
the bargraph will be at 50% when the two signals are equal, will be > 50% when PV > SP, and will be < 50% when
PV < SP.
Parameter 1 is the "Proportional Band", that is the % deviation required to drive the Output from 50% to 100%. The
DEV
formula is:
Block Output = ((PV
– SP) * (50 / Parameter 1)) + 50%
DEV
Examples:
PV
SP
Parm. 1
Output
52
50
2.00
100.00
50
50
2.00
50.00
48
50
2.00
0.00
73
70
5.00
80.00
---------------------------------------------------------------------------------------------
NAME: DEV SINGLE USE FUNCTION: N OUTPUT TYPE: A
---------------------------------------------------------------------------------------------
Input Type Description Notes
_____________________________________________________________________________________________
1 A PV INPUT
2 A SP INPUT
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 % OF PV=MAX DEVIATION 2.00 50.00 0.20 2 1
Notes:
1. PV-SP error is limited to +/- 300% internally.
F58
[COUNT] Pulse Counter
Function
COUNT
adds 0.01% to the Block Output during the first scan that the Pulse Input changes from a 0 to a
1 (i.e. on the rising edge), assuming (Parameter 1) the Pulse Divisor = 1. If the Pulse Divisor = 5, then 5 pulse rising
edges must be received before the Output is incremented by 0.01.
The Block Output rolls over from 99.99% to 0.00% after 10,000 pulses. The Block output is forced to 0.00% when
the Reset Input equals 1.
A typical application would be to count flow totalizer pulses, and then connect the
COUNT
Block Output to a Tag in
a Front Panel Display channel. See the
TOT
function.
At power down, the Block Output is saved in the Retentive Memory area of the NVRAM. During the first scan after
CPU start-up, the
COUNT
Block Output is set to the value stored in the Retentive Memory.
---------------------------------------------------------------------------------------------
NAME: COUNT SINGLE USE FUNCTION: N OUTPUT TYPE: A
---------------------------------------------------------------------------------------------
Input Type Description Notes
_____________________________________________________________________________________________
1 D PULSE INPUT (^1=COUNT) 1
2 D RESET INPUT (1=RESET)
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 PULSE DIVISOR 1 19999 1 2
Notes:
1. Increments Output on the rising edge of the Input
(i.e., the first scan when Input becomes a 1)
