Motrona MM 640, Operating Instructions Manual

Page: 37 / 44

MM64003a_e.doc / Feb-09 Page 37 / 44
8.2. Standstill Definition (Wait-Time)
This definition is related to the input frequency only and does not depend on any other scaling
parameters. It is necessary to set the period time of the minimum frequency that the unit still
should consider as “motion”.
Where e.g. we set „Wait Time1“ to 0.1 sec., the unit will declare all encoder1 frequencies
lower than 10 Hz for “Motion” and all frequencies higher than 10 Hz for “Standstill”.
8.3. Scaling of the Position Counters
8.3.1. Direct impulse counting
When you like the counters (Counter 1 and Counter 2) to count just the encoder increments
without any scaling, please set the associated impulse scaling factors (F06.76 respectively
F07.091) to 1,00000, and set the associated impulse multiplier (F06.007 respectively F07.092)
to „1“. All positional and differential counts as well as the attached setpoints (Setpoint Position
und Differential Setpoint) will then be straight incremental.*)
8.3.2.
Differential evaluation
When the two encoders provide different ppr numbers, or when a gearbox is installed between
encoder1 and encoder2, any differential evaluation requires adaptation of both encoders by
proper scaling.**)
You must know the accurate number of impulses generated by both encoders in one cycle or on
a defined distance (e.g. one full revolution of the slower encoder or a traveling distance of
1000 mm). The following formula applies:
Impulse count encoder1 x Factor Counter1 = Impulse count encoder2 x Factor Counter2
!
A simple solution exists by using the figures of the impulse count on one side as a factor
setting on the other side. If e.g. on a fixed traveling distance encoder1 would generate 20 000
impulses whereas encoder2 would generate only 300 impulses, use 0.03000 for the Factor
Counter1 and 2.00000 for the Factor Counter2. For precision applications it may be important to
avoid cumulating errors caused by ratios with more than 5 decimal positions.
8.3.3.
Scaling to customer engineering units
The parameters „Factor Counter“ and „Multi Counter“ are used the same way for scaling of the
position counters to customer units. If e.g. you like to receive a 0.1 mm scaling with an existing
resolution of 20 000 increments per meter, just set the corresponding factor to 0.50000
(20 000 x 0.5 = 10 000, which appears as 1000.0 mm when you switch the decimal point on)
*) under consideration of the selected edge-counting mode (F06.088 respectively F07.103)
**) only important for differential evaluations (encoder 1 – encoder 2)