314 Properties of the Modules
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
Monitoring of selected cylinders
imc CANSAS-IGN can monitor selected cylinders by means of the camshaft position. The camshaft signal
is only relevant if this monitoring has been configured. The condition for the monitoring is tat the ignition
signal includes all of the cylinders' ignition pulses.
Snapshot-Mode
To parameterize imc CANSAS-IGN appropriately, a so-called Snapshot-mode can be configured. In that
case, the module takes brief snapshots of the input signal at high data rate in a storage volume. Next, the
storage content is read back at a slower data rate via the CAN-Bus. This provides the user with a very
good view of the signal's course, making it possible to set sensible levels for recognizing signal edges. But
it also becomes possible to check in advance the effects of smoothing filters, AC-circuits, etc..
6.11.1 Interference suppression
The inputs' electrical insulation prevents interference from adjacent channels to be picked up.
An anti-aliasing filter of ca. 500 kHz provides some interference suppression.
Low-pass filters can be parameterized to provide interference suppression.
Parameterized hysteresis filter suppress noise and interference peaks with a lower level than the
hysteresis width.
When pulses follow upon each other rapidly, only the first is taken into consideration. In that case, the
maximum RPMs are dtermined and subsequent pulses are ignored if they are nearer than 50 % of the
expected regular distance.
Further, with the ignition angle an range of at least ca. 10 degrees (but a maximum of 20 ms) is covered,
within which subsequent pulses are ignored. The ignition produces strong oscillations, but only the first
edge of the first pulse determines the ignition time, while the many subsequent oscillations no longer do.
Correct grounding is also important. See Grounding bolt .
315
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