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10-2 PLC Mode Description

MN766

A and B are deﬁ ned as follows:

A = (Value of Parameter P3431) / (Max of Parameter P3431)
B = (Value of Parameter P3433) / (Max of Parameter P3433)
Then, A & B are signals with the following properties: -1≤ A ≤1 and -1≤ B ≤1.
A and B are normalized signals derived from parameters pointed to by P3431 and P3433.

Comparator A

Comparator A is used in Condition 76 and checks the following relationship for true or false:
If | A - P3435/100 | ≤ P3432/100
Alternatively, another way of writing the same relation is as follows:
If (P3435 - P3432)/100 ≤ A ≤ (P3432 + P3435)/100
Thus, Comparator A provides a way to determine if a parameter is within a specifi c range. For example, if P3431=5 (Motor
Volts with Max=230V) and P3432=20% and P3435=0% then Comparator A would be true so long as |P5| ≤ 46V or |A| ≤ 0.20.
That is, motor voltage is monitored and so long as it remains below 46 Volts, the outcome of Comparator A would be True,
but if it were to go above 46 Volts, the output of Comparator A would be False.

Comparator B

Comparator B is used in Condition 77 and checks the following relationship for true or false:
If | B - P3436/100 | ≤ P3434/100
Alternatively, another way of writing the same relation is as follows:
If (P3436 - P3434)/100 ≤ B ≤ (P3436 + P3434)/100
Thus, Comparator B provides a way to determine if a parameter is within a specifi c range. For example, if P3433=6 (Motor
Current with Max=10Amps) and P3434=10% and P3436=50% then Comparator B would be true so long as:
4 Amps ≤ P6 ≤ 6 Amps
OR
0.4 ≤ B ≤ 0.60.
That is, motor current is monitored and so long as it remains within 1 Amp of 5 Amps the outcome of Comparator B would
be True, but if it were to go above 6 Amps or below 4 Amps the output of Comparator B would be False.

Less than

Less than, Condition 88, uses the following equation: If A<B then True else False For example, if P3431=103 (Analog Input 1
Reference with Max=100%) and P3433=104 (Analog Input 2 Reference with Max=100%) then Condition 88 would be true so
long as P103<P104 or so long as Analog Input 1 Reference is less than Analog Input 2 Reference.

Equal

Equal, Condition 89, uses the following equation: If A=B then True else False For example, if P3431=103 (Analog Input 1
Reference with Max=100%) and P3433=104 (Analog Input 2 Reference with Max=100%) then Condition 89 would be true so
long as P103=P104 or so long as Analog Input 1 Reference is equal to Analog Input 2 Reference.

Greater than

Greater than, Condition 90, uses the following equation: If A>B then True else False For example, if P3431=103 (Analog
Input 1 Reference with Max=100%) and P3433=104 (Analog Input 2 Reference with Max=100%) then
Condition 90 would be true so long as P103>P104 or so long as Analog Input 1 Reference is greater than Analog Input 2
Reference.

10.4 Timers

The PLC Mode uses four general purpose timers: Timer A (P3440), B (P3441), C (P3442) and D (P3443) with units of
seconds and resolution of 10ms or 100 counts/sec. They may be used in PLC control and logic statements as defi ned in
the Conditions and Actions Tables. In general there are actions to start and stop the timers as well as conditions to test their
contents.
P113, P114, P117 and P118 are read/write monitor parameters that refl ect the current state of timers A through D. Since
they may be written, they can be used to start a timer by writing zero to it or to stop a timer by writing max counts.
For example, set P3440 to 1.5 sec then upon Timer A timeout,
P113 = 150 counts = (1.5 sec) x (100 counts/sec)
Starting timer A also starts P113 ramping from 0 to 150 in 1.5 seconds.
Set P3441 to 10 seconds and start Timer B, P114 then ramps from 0 to 1000 in 10 sec.
These monitor parameters may also be inputs to the Composite Reference block to generate timed ramps or other complex
reference signals.