IMC CANSAS - Page 326

326 Properties of the Modules
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
The camshaft's pulse sequence shows positive edges at 60, 140, 320 and 600 degrees. The same pulse
sequence shows negative edges at 100, 280, 460 and 640 degrees. The decision whether positive or
negative edges are used is easy to make: the distances between the positive edges are 80 = 140-60,
180 = 320-140, 280 = 600-320, 180 = 60 + 720 - 600. Conversely, the distances between the negative
edges are 180 = 280 - 180, 180 = 460-28, 180 = 640-460, 180 = 100+720-640 degrees. All negative
edges thus have the same distances. So, it is not possible to recognized at which position the camshaft
is located simply by observing the negative edges. But the positive edges have significant differences
in their respective distances. For this reason, the camshaft channel parameter Trigger signal edge is
set to "positive". In the input box for the camshaft pattern, the text 60 140 320 600 (the sequence
of positive edges) is entered.
Alternatively, the sequence -120 60 140 320 can be specified, since -120 and 600 denote the same
position.
It is not necessary to state either the zero-marking or its position exactly. In order to state the ignition
angle exactly, only the crankshaft position is always used. Conversely, the camshaft position is only for
the purpose of determining which cylinder currently is receiving an ignition impulse. A tolerance of
roughly 40 degrees is acceptable. Thus, it is sufficient to state the position to within 40 degrees.
For engines having adjustable camshafts (also variable camshaft control or variable valve control), the
angle between the crankshaft and the camshaft changes within certain limits. The ignition angle
module covers this case.
Note when stating the angle positions for the camshaft that the distances between individual signal
edges, in particular, must be stated precisely. Thus, it is less important whether the sequence
specified is 60, 140, 320 or 70, 150, 330.