212
8.3.19
Loop disconnection detection function
Using this function detects an error occurring within a control system (control loop) due to reasons such as a load
(heater) disconnection, an externally-operable device (such as a magnetic relay) failure, and input disconnection.
(1) How an error is detected
From the point where the control output has reached upper limit output limiter value or lower limit output limiter
value, the amount of changes in the temperature process value (PV) is monitored every unit time set and
disconnection of a heater and input is detected.
(2) Examples of the errors detected
The following are the examples of the errors detected.
(a) When control output is being performed
The temperature control module detects an error because the temperature does not rise even when control
output is being performed under the following conditions:
• When a heater is disconnected
• When input is disconnected or short-circuited
• When the contact point of an externally-operable device does not turn on
After the control output has reached upper limit output limiter value, if the temperature does not rise by 2
(
)
or more within the loop disconnection detection judgment time set, an alert is output. (The operation is reversed
for forward action. (
(b) When control output is not being performed
The temperature control module detects an error because the temperature rises even when control output is
not being performed under the following conditions:
• When input is disconnected
• When the contact point of an externally-operable device was bonded
After the control output has reached lower limit output limiter value, if the temperature does not drop by 2
(
)
or more within the loop disconnection detection judgment time set, an alert is output. (The operation is reversed
for forward action. (
(3) Setting method
Two settings are available for the loop disconnection detection function.
(a) Setting for the unit time to monitor the amount of changes in the temperature
process value (PV)
1.
Set "Method selection" to "Param write" of the control mode to be used.
"CC IE Field Configuration" window
Select the temperature control module from "List of
stations"
[CC IE Field Configuration]
[Online]
[Parameter Processing of Slave Station]
2.
Set "CH
Loop disconnection detection judgment time".
When not using this function, set "CH
Loop disconnection detection judgment time" to 0.
Standard
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