IDEC MICROSmart FC6A Series Ladder Programming Manual page 400

19: PID C I
ONTROL NSTRUCTION
Type
Turns ON the alarm output when process variable ≤
(set point + alarm value).
Turns OFF the alarm output when process variable ≥
(set point + alarm value + hysteresis).
When (set point + alarm value) < process variable <
(set point + alarm value + hysteresis), the alarm
output maintains the state of the previous scan.
The gray-colored portion is where the standby
function operates.
Lower Limit Alarm
with Standby
- Alarm action point
Turns ON the alarm output when process variable ≥
(set point + alarm value).
Turns ON the alarm output when process variable ≤
(set point - alarm value).
Turns OFF the alarm output when (set point - alarm
value + hysteresis) ≤ process variable ≤ (set point +
alarm value - hysteresis).
When (set point + alarm value - hysteresis) < process
variable < (set point + alarm value), the alarm output
maintains the state of the previous scan.
When (set point - alarm value) < process variable <
(set point - alarm value + hysteresis), the alarm
Upper/Lower Limit
output maintains the state of the previous scan.
Alarm with Standby
The gray-colored portion is where the standby
function operates.
Alarm action point
Notes:
• Alarm action point
This indicates the point where the alarm output changes from OFF to ON.
• Standby function
This function does not immediately turn ON the alarm output when starting execution of the PIDA instruction, even when the process
variable is in the alarm output ON range.
The standby function is canceled when the process variable enters the alarm output OFF range, and when the process variable enters the
alarm output ON range, the alarm output will turn ON.
If the set point is changed, the standby function will be enabled again.
Process variable
ON
PID instruction input
OFF
ON
Alarm output
OFF
19-10
Action
Alarm value
Hysteresis
ON
OFF
Set point + Alarm action point
Alarm value Alarm value
Hysteresis Hysteresis
ON
Set point Alarm action point
(Alarm output ON range)
Cancel standby
FC6A S MICROS
ERIES
Set point: 200.0°C
Alarm value: -5.0°C
Hysteresis: 2.0°C
When process variable ≤ 195.0°C, the alarm output is turned ON.
When process variable ≥ 197.0°C, the alarm output is turned OFF.
Set point: 200.0°C
Alarm value: 5.0°C
Hysteresis: 2.0°C
When process variable ≥ 205.0°C, the alarm output is turned ON.
When process variable ≤ 195.0°C, the alarm output is turned ON.
When 197.0°C ≤ process variable ≤ 203.0°C, the alarm output is
turned OFF.
(Alarm output OFF range)
L P
MART ADDER ROGRAMMING
Example
2.0°C
ON
OFF
195.0°C 197.0°C 200.0°C
2.0°C
ON
OFF
195.0°C 197.0°C
(Alarm output ON range)
M FC9Y-B1726
ANUAL
5.0°C
5.0°C 5.0°C
2.0°C
200.0°C 203.0°C 205.0°C