Mitsubishi Electric MELSEC Q Series User Manual page 59

3 SPECIFICATIONS
Process value (PV)
Temperature
set value (SV)
Alert set value
Alert status
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(c) Wait alert
Choosing the wait alert ignores the alert status if the process value
(PV)/deviation is in that status when the setting mode is changed to the
operation mode, and makes the alert function invalid until the process value
comes out of the alert status once.
Example: Selecting the lower limit deviation alert with wait makes the alert
[Lower deviation alert]
Process value (PV)
Non-alert status
POINT
When the system has reached the non-alert status even once after an alert
judgment start following the setting of the alert mode, the alert function with wait will
be invalid if you choose the mode with wait.
(d) Re-wait alert
The re-wait alert is a wait alert-based feature which has the additional
function to make the alert function invalid again when the set value (SV) is
changed.
For set value changing control, choosing the re-wait alert avoids the alarm
status reached when the set value is changed.
Example: If the process value (PV) is at the position as shown below before
Before temperature
set value (SV) change
After temperature
set value (SV) change
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function invalid until the process value exceeds the alert set value.
Process value (PV)
Temperature
set value (SV)
Alert set value
Time
Alert status Alert status
the setting is changed, changing the temperature set value (SV) for
deviation alert will put the process value in the alert region and turn
on the alert. To prevent this, the function makes the alert wait
operation valid and the alert output to wait.
Process value (PV)
Alert region
Alert set value
Process value (PV)
Alert region
MELSEC-Q
[Lower deviation alert with wait]
Process value (PV)
Wait operation region
Temperature set value (SV)
Temperature
set value (SV) change
Alert set value Temperature set value (SV)
Time
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