IMC CANSAS - Page 193

Measurement modes 193
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
Setting the number of pulses:
IncrementalEncoder0x > Index card "Inputs" > Combo box "No. of encoder pulses"
The number of encoder pulses must be between 1 and 999999.
The input range selected states the input range end value. The highest frequency/RPM-value/
velocity contained in the measured signal may not exceed this end value. The sampling interval can
take discrete values between 1 ms and 1 min and states the rate at which result values are returned.
Setting the sampling interval:
IncrementalEncoder0x > Index card "Inputs" > Combo box "Sampling interval"
Behavior in response to missing signal pulses
If a sequence of signal pulses is slowing down and then one sampling interval elapses without any pulse,
no calculation can be performed for that sampling interval. In that case, the system assumes that the
rotation speed is simply decreasing and an attenuating signal course is extrapolated. This "estimated"
measurement value is then closer to the true value than the value determined from the preceding
sampling interval. This technique has demonstrated its validity in practice.
Note
In extreme cases, the sensor does not return any more pulses, e.g. in case of a sudden outage. Then the
algorithm generates an attenuation curve, meaning values > 0, even if the measurement object is
actually no longer moving.
5.1.3.1.2 Measurement procedures
Differential measurement procedures
The quantities derived from event-counting, Events, Distance and Angle denoted by the annotation
(diff.) are "differential" measurements. The quantity measured is the respective change of
displacement or angle within the last sampling interval. (positive or, for dual track encoders, negative
also) or the newly occurred events (always positive).
If, for instance, the total displacement is desired, it must be calculated by integration of the
differential measurements using Online FAMOS functions.
Cumulative measurements
The quantities derived from event-counting, Events, Distance and Angle appearing with the
annotation (sum) are "cumulative" measurements. In cumulative measurement, the return value is
the sum of all displacement or angle changes, or of all event which occurred.