Loop Disconnection Detection Function - Mitsubishi Electric MELSEC iQ-R Series User Manual

1.29

Loop Disconnection Detection Function

This function detects errors that occurs in a control system (control loop) such as a load (heater) disconnection, an
externallyoperable device (such as a magnetic relay) failure, and input disconnections.
How an error is detected
From the point where the control output has reached the upper limit output limiter value or the lower limit output limiter value,
the variation amount in the temperature process value (PV) is monitored every unit time set and heater and input
disconnections are detected.
Examples of the errors detected
The following shows the examples of the errors detected.
■When control output is executed
The temperature control module detects an error because the temperature does not rise even while control output is being
executed under the following conditions:
• When a heater is disconnected
• When input is disconnected or short-circuited
• When a contact point of an externally-operable device does not turn ON
When the temperature does not rise by 2 () or higher within the set loop disconnection detection judgment time after the
control output has reached the upper limit output limiter value, an alert is output. (The operation is reversed for a forward
action.  Page 54 Direct/reverse Action Selection Function)
■When control output is not being executed
The temperature control module detects an error because the temperature rises even while control output is not being
executed under the following conditions:
• When input is disconnected
• When a contact point of an externally-operable device was welded
When the temperature does not fall by 2 () or lower within the set loop disconnection detection judgment time after the
control output has reached the lower limit output limiter value, an alert is output. (The operation is reversed for a forward
action.  Page 54 Direct/reverse Action Selection Function)
Setting method
Configure two settings to use the loop disconnection detection function.
■Setting the unit time to monitor the variation amount in the temperature process value (PV)
Configure the setting as follows:
[Navigation window]  [Parameter]  Target module  [Application Setting]  [Loop disconnection detection setting] 
[Loop disconnection detection judgment time]
When this function is not necessary, set 0 for "Loop disconnection detection judgment time" of "Loop
disconnection detection setting" in "Application Setting."
1 FUNCTIONS
1.29 Loop Disconnection Detection Function
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