Simplex 4007ES Programmer's Manual page 88

Custom Control, Continued
Using a Ladder
Logic Diagram to
Evaluate an
Equation
The example shown above can be interpreted as: If point M2-1 or M2-2 or M2-3 and M2-4 are
in a trouble state, hold on Relay 1. M2-4 is the key here. At least one of the three on the left
(M2-1, M2-2, and M2-3) must be in a trouble state AND M2-4 must also be in a trouble state.
• Use a circle to represent each output statement. Add text within or beside the circle to
describe the output statement. In the following example, the output side of the equation
contains a single output statement, HOLD ON SIG 1. This action only occurs if the
input side of the equation, which monitors point M 2-1 for the presence of a fire
condition, is true.
• Represent the OR logical operator by positioning inputs on top of one another as
shown in the example below. Represent the AND logical operator by positioning the
inputs beside one another.
Vertical, parallel
lines represent input
Solid line
represents the
Point Status
start of the
equation
Point Status
M 2-1 for TBL
Position the
inputs on Point Status
M 2-2 for TBL
top of one
another to
Point Status
represent
M 2-3 for TBL
the OR
logical operator
4007ES Panel Programmer Manual (579-1167)
Dashed line
separates input side
from output side
Hold ON
M 2-1 for
SIG1
FIRE
Point Status
M 2-4 for TBL
Position the inputs beside
one another to represent AND
logical operator
Figure 9-6. Logic Diagram
9-4
Circles represents outputs
Relay