AMCI NEXUS NX2A4E2, User Manual

Page: 9 / 76

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
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NX2A4E2 User Manual
NX2A4E2 I
NTRODUCTION
9
Stop Time Monitoring
If you are using the NX2A4E2 in a press control application, you can use the stop time monitoring feature to
measure the stopping time of the crankshaft. The stop time monitor on the unit measures the time between the
on-to-off transition of the Brake Input and the stopping of the transducer attached to channel one. Note that
channel one must be configured as a single-turn channel to use the stop time monitor. The Stop Time Timer
measures a stopping time of 34 milliseconds to 9.999 seconds with a resolution of 1 millisecond.
The NX2A4E2 also captures the position at which the brake is applied and reports this information, along
with the stopping time, when a brake cycle is completed. This information is reported over the network until
the next brake cycle finishes.
If you are not using the unit in a press control application, you can leave the Brake Input un-wired and the
Stop Time monitor will never be triggered.
Figure R1.2 below shows how the stopping time is measured.
Figure R1.2 Stop Time Measurement
1) The NX2A4E2 captures the Brake Applied Position and starts the Stop Time Timer when the Brake Input
makes a 1

0 (on

off) transition. The Brake Applied Position is not immediately placed in the input data.
It is updated, along with the Stop Time, when the brake cycle completes.

If the Brake Input returns to its normal state for sixteen milliseconds in the next thirty-four, the
input transition is considered noise and the brake cycle is aborted. The next transition on the
Brake Input starts another brake cycle.

If the Brake Trigger Input is not in its active state for twelve of the last sixteen milliseconds of
the thirty-four millisecond debounce time, the input transition is considered noise and the brake
cycle is aborted. If the input is in its active state at the end of the thirty-four milliseconds, the
brake cycle will begin again immediately. If the input is in its normal state, the brake cycle will
start on the next transition.
2) Once the debounce time is exceeded, the state of the brake trigger is ignored until the brake cycle is
complete. From this point on, the Stop Time timer runs until the transducer position stops changing. The
‘

Position’ section of the diagram shows the press coming to a stop.
3) The Stop Time timer stops when the change in position value equals zero. The transducer is considered
stopped when there is less than 1/2,048th of a rotation made in 125 milliseconds. This translates into less
than one turn every 4.2 minutes. Obviously, it takes 125 milliseconds to determine that the position has not
changed for that amount of time. Therefore, the Stop Time timer runs until the transducer does not move
for 125 milliseconds, and it then subtracts 125 milliseconds from the Stop Time value.
The stop time monitor is a monitoring feature only. Any determination of correct brake
operation must be made by the host controller through a user developed program.
Debounce Time
Brake Trigger Input = 33 mSec
Measured Stop Time
Brake Applied Position
Position
P=0
Input State is 'Don't Care' from the end of the
Debounce Time until press has stopped.