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MELSEC-Q
3 SPECIFICATIONS
3.5.30 Loop disconnection detection judgment time
(buffer memory address 59, 91: Un\G59, Un\G91)
(1) The loop disconnection detection function detects errors in the control system
due to a load disconnection, external operation device fault, sensor
disconnection and the like.
No temperature change of greater than 2
for thermocouple input and greater
than 0.2% of full-scale for micro voltage, voltage and current within the loop
disconnection detection judgment time is judged as a loop disconnection.
(2) As the loop disconnection detection judgment time, set a value longer than the
time taken to vary the temperature 2
(2 F) or that of 0.2%.
(3) Performing auto tuning automatically sets a value twice longer than the integral
time as the loop disconnection detection judgment time.
However, if the loop disconnection detection judgment time was set to 0 at the
auto tuning, the loop disconnection detection judgment time is not stored.
(4) The setting range is 0 to 7200 (0 to 7200s)
POINT
If loop disconnection alert occurs frequently despite the normal operation of sensor
and external operation device, confirm whether the capacity of external operation
device (heater, cooling fan, etc) is enough.
If they are deficient, make the setting value of loop disconnection detection
judgment time longer than time required for varying 2
or 0.2% with manipulated
value 100%.
3.5.31 Loop disconnection detection dead band
(buffer memory address 60, 92: Un\G60, Un\G92)
(1) To prevent the false alarm of loop disconnection detection, set the non-alarm
area (width where loop disconnection will not be detected) around the set value.
(2) The setting range is
full-scale
Time
Process value (PV)
Set value (SV)
Loop disconnection detection
dead band setting
Non-alarm area
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