Programming Technique
Chapter 25
25-7
Here is an explanation of each rung:
Rung 1: The Get instruction at address 201 multiplies the value of
100
o
C by 9 and stores 900 at address 203.
Rung 2: The Get instruction at address 204 divides 5 into 900 and
stores the quotient, 180, in address 205.
Rung 3: The Get instruction at address 207 adds 32 to the value
180 which is located at get addresses 205. The sum of 212
is stored at address 210. Thus 100
o
C = 212
o
F.
Rung 4: If the displayed temperature is less than 190
o
F, the timer
initiates timing for three seconds.
Rung 5: If three seconds have elapsed, an output at address 011/15
will energize a heating device which will bring the
temperature back into the desired range.
Rung 6: Counter 034 counts the number of times the value falls
below 190
o
F. Therefore, when rung 4 is true the
counter increments.
Rung 7: When the temperature equals 212
o
F latching 011/16
enables an alarm.
Rung 8: To shut the alarm off, unlatch 011/16. To do this, an
operator would press a pushbutton connected to
address 011/16.
Application Two (
o
C to
o
F Every Five Seconds)
This application is similar to application one, but we are only recording the
converted temperature reading every five seconds (Figure 25.7).
