Automating Manufacturing Systems - Process Control and ...

plc basic functions - 15.18
CMP
expression
N7:03 = N7:02
CMP
expression
N7:03 N7:02
CMP
expression
N7:03 < N7:02
CMP
expression
N7:03 N7:02
CMP
expression
N7:03 >= N7:02
O:012
00
O:012
01
O:012
02
O:012
03
O:012
04
O:012
05
Figure 15.17
Equivalent Statements Using CMP Statements
Expressions can also be used to do more complex comparisons, as shown in Figure
15.18. The expression will determine if F8:1 is between F8:0 and F8:2.
CMP
expression
(F8:1 > F8:0) & (F8:1 < F8:2)
O:012
04
Figure 15.18
A More Complex Comparison Expression
The LIM and MEQ functions are shown in Figure 15.19. The first three functions
will compare a test value to high and low limits. If the high limit is above the low limit and
the test value is between or equal to one limit, then it will be true. If the low limit is above