Keba Kemro MM 240/A - 6.3 Speed measurement; 6.5 Pulse counter with direction evaluation; 6.6 Zero pulse monitoring; 6.7 Latch function digital input

6.3 Speed measurement
The velocity measurement function can be used to obtain a good accuracy of
the evaluation when using a rotary encoder with a low resolution. This is done
by measuring the period duration between two incremental encoder pulses by
means of an internal time basis. The velocity measurement can be made in
either direction.
The velocity value is measured four times for each period duration. If the di-
rection is changed during an ongoing measurement, the measurement is
started anew. Once the measurement is completed the value is marked as
new. The input pulses are scanned with an internal timing of 50 MHz. At a
maximum input frequency of 250 kHz this will result in a resolution of at least
8 Bit. Frequencies that are smaller than 3 pulses per second are evaluated as
zero velocity.
6.4 Pulse counter without direction evaluation
This function makes the pulse counter at track A available (edgeCount=4). No
direction information is taken into account. Track B and Track Zero are not
evaluated.
6.5 Pulse counter with direction evaluation
This function makes the pulse counter at track A available (edgeCount=5). The
status of track B decides on the direction of counting.
Track B = 0: -> forward, Track B = 1: -> backward.
Track Zero is not evaluated.
6.6 Zero pulse monitoring
When a rotary encoder with Zero pulse is used, the configuration of the number
of pulses per rotation ( incrementsPerRev) will activate the monitoring, which
compares the number of counted pulses with the number of configured pulses.
If the numbers of pulses differs, an error message will be triggered.
This allows monitoring the correct function of the connected transducer.
6.7 Latch function digital input
A latch function is available ( latchEdge) to record the counter status when an
edge occurs at one of the latch inputs (DI0, DI1) of the MM 240/A.
The current counter status is recorded at the first edge. When the counter
status is read out at the next update cycle the trigger will be activated again. If
MM 240/A
Functional description
© KEBA 2010
Project engineering manual V1.08 23