Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual - Manual (Page 250)

EAF
Process Control Instructions
Chapter 16
16-39
Figure 16.11
3 Digit Standard Deviation Ladder Diagram
032
005
G
044
EXECUTE AUX
FUNCTION NUMBER:
DATA ADDR:
RESULT ADDR:
07
0047
0040
FUNCTION
15
033
TON
0033
1.0
PR 003
AC 000
15
034
CTU
0034
PR 005
AC 000
15
033
DN
0034
15
FILE TO WORD MOVE
COUNTER ADDR:
POSITION:
FILE LENGTH:
0034
005
005
FILE A: 0201-0205
FILE A: 0036
15
033 035
001
G
^
^
^
Changing Data
Always 1
Number
of Samples
0047
000
G
070
00
0040
000
G
070
00
0041
000
G
THREE DIGIT STANDARD DEVIATION:
036
000
G
0042
000
G
0043
000
G
0044
000
G
0045
000
G
^ ^ ^ ^
RES ULT
Intermediate Results
Indicates that these values need to be reset to zero in between calculations. 1
1 1 1 1 1 1
1
1
15
Here is a description of the ladder diagram. This programming example
calculates the standard deviation of five values and stops.
Rung 1 Contains a free-running timer (033) that allows a different
value to be summed every 3 seconds. The preset of this timer
can be as small as 10 milliseconds.
Rung 2 The Timer Done Bit (03315) increments counter 034 every 3
seconds to externally index the File-to-Word Move in rung 3
that moves each value into the standard deviation instruction.
The preset of the counter must equal the length or number of
samples in word 032 in the EAF rung. The accumulated
value of the counter must start at zero.