Mitsubishi Electric MELSEC Q Series User Manual page 58

3 SPECIFICATIONS
Process value (PV)
Alert set value
Alert status
Temperature set value (SV)
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(2) The Q64TC allows the alerts function in (1) to be set with the addition of an alert
dead band, alert delay count or wait/re-wait.
The following table indicates the alerts function which can be used with the
addition of alert dead band, alert delay count and wait/re-wait.
Alerts function
Upper limit alert
Input alert
Lower limit alert
Upper limit
deviation alert
Lower limit
Deviation
deviation alert
alert
Upper/lower limit
deviation alert
Within-range alert
(a) Alert dead band setting
When the process value (PV)/deviation is close to the alert set value, the alert
status may alternate with the non-alert status due to input instability or the like.
Setting the alert dead band prevents the alert status and non-alert status from
alternating with each other due to input instability or the like when the process
value (PV)/deviation is near the alert set value.
Example: When the dead band value is set to the upper limit input alert, the
[When alert dead band value is not set]
Process value (PV)
(b) Alert delay count setting
The system is set in the alert status when the process value (PV) that has
reached the alert set value remains in the alert range until the sampling count
becomes equal to or greater than the preset alert delay count.
Example: When the alert delay count set to the input upper limit alert is 5, the
Process value (PV)
Alert set value
Input sampling
Alert status
search engine
Dead band setting
system is placed in the alert status when the upper limit of the input
rises to or above the alert set value. The system is put in the non-
alert status when the upper limit falls below the alert dead band.
Process value (PV)
Alert set value
Time
Alert status
system is not placed in the alert status if the sampling count is 4 or
less.
Process value (PV)
3 times
MELSEC-Q
Alert delay count Wait
——
[When alert dead band value is set]
Process value (PV)
Non-alert status Alert status
5 times
Re-wait
——
——
——
Dead band
Time
Time
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