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CMU-212 Cabinet Monitor Unit
Operations Manual
invalid FCS calculation, invalid parameter values, or a Datakey Protocol Version
incompatibility.
The Datakey not present will cause a LFSA and illuminate the DIAGNOSTIC indicator if the
DOOR SWITCH FRONT input is sensed as not active (door closed). The DIAGNOSTIC
indicator will flash at a rate of 2Hz if the Datakey is not present when the DOOR SWITCH
FRONT input is sensed as active (door open).
2.14.4 INTERNAL MPU MONITOR
The CMU-212 will monitor the operation of its microprocessor with an independent circuit.
At a minimum, the monitoring circuit will receive logic state transitions at least once every
50 milliseconds from the microprocessor. When the logic state transition is not received for
500 milliseconds the monitor circuit will force a LFSA-R and illuminate the DIAGNOSTIC
indicator.
2.15 RECURRENT PULSE DETECTION
This error detection function supplements the normal Conflict, Multiple, and Lack of Signal
monitoring algorithms for sensing faults that are intermittent or pulsing in nature. The RMS
signal detection algorithm is designed to filter out short term transients commonly found on
the electrical service and provide noise immunity against false signal detections. The
Recurrent Pulse detection function is designed to respond to fault conditions that are
intermittent in nature and do not meet the continuous timing requirements of the normal
detection algorithms, yet may still produce improper signal displays. These input conditions
are differentiated by their longer time constant and fault response times.
The figure below shows a simple example of a recurrent Conflict fault. Channel 2 Green is
detected active due to a malfunction of the load switch that caused the output to "flicker" On
for 100 ms approximately every 200 ms. Because normal Conflict detection requires a
continuous fault of at least 350 ms duration, this event could go undetected. The Recurrent
Pulse detection algorithm will combine these pulses into one event and trigger a Conflict
fault once the longer recurrent timing threshold is exceeded.
When triggered by a recurrent fault condition, the Signal Monitor will enter the fault mode,
transfer the Output relay contacts to the Fault position, and illuminate the appropriate
CONFLICT, MULTIPLE, or LACK OF SIGNAL indicator. The unit will remain in the fault
mode until reset by the Reset button or the External Reset input. Fault response times will
vary depending on the pulse width and frequency of the recurrent inputs, but will range
from 1000 ms minimum to 10.4 seconds maximum. Recurrent Pulse detection can be
disabled with the SEL1 option jumper, see Section 2.15.1.
2.15.1 RECURRENT PULSE DETECTION DISABLE
The Recurrent Pulse Detection function can be disabled by soldering a 0-ohm jumper into
position SEL1 on the CMU-212 printed circuit board. When the jumper is inserted,
Recurrent Pulse Detection is disabled. When the jumper is removed, Recurrent Pulse
Detection is enabled.
Eberle Design Inc.
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