W
ATLOW
®
EZ-ZONE
®
RMZ4
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33
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E
THER
CAT
®
A
DAPTER
8.3
O
PEN
L
OOP
D
ETECT
RMZ4 has the capability to detect if the control loop is out of control. The loop is detected as being “open” if
the manipulated value of output power is not having an effect on the measure process value. Open loops can
be caused by various issues. Open fuses, heaters or interlock contactors will prevent power from reaching the
load. Sensors that are not in proper contact with the load will not detect changes in temperature correctly.
This will cause thermal runaway. Since loads change at different rates and respond to power differently the
feature is configured with an amount of change expected in a period of time. Typically the process value will
not increase at all in response to 100% output power. Set the value conservatively to prevent false trips. For
example, If the process would normally change 20 degrees per minute at 100% power, the feature could be set
to 5 degrees in 60 seconds. This would trip if the measured process value does not change at less than ¼ its
normal rate.
Configuring
Parameter
ECAT
Index
DNET
Class
Sub
/Attr
Description
Open Loop Detect Enable
0x4nn1
0x68
0x2F
1 = Enables the Open Loop Detect Feature
0 = Disables the feature
Open Loop Detect Time
0x4nn1
0x68
0x30
Sets the amount of time given for the process
value to change by at least the Deviation
amount.
Open Loop Deviation
0x4nn1
0x68
0x31
Sets the amount the process value must change
within the Detection Time or an open loop
error will be set.
Using
Parameter
ECAT
Index
DNET
Class
Sub
/Attr
Description
Open Loop Error Status
0x2nn0
0x65
0x04
0 = Control Loop is operating properly
1 = Control Loop is not closed, output power
set to 0%.
Clear Open Loop Detect Error 0x3nn0
0x66
0x01
Clear the open loop error. The loop will
function again. If the condition has not be
correct the error will occur again after the
power reaches 100% for the detection time.
