IMC CANSAS - Tips

330 Properties of the Modules
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
6.11.5 Tips
Rotation speed or ignition angle not readable
The numerical values are only clearly visible to the human eye if the same value remains visible
sufficiently long. A display refresh interval of 500ms is recommended in order to be able to even read
rapidly changing numerical values.
As well, a longer averaging period can contribute to making the readout more stabile. It is especially
helpful to make the averaging period and the display refresh rate match.
If the values do not change as rapidly, it is also possible to set both to 200ms.
Readout of rotation speed shows "---" in the Display
Either no signal or an implausible value, i.e. the currently calculated RPM is higher than the value
configured for the parameter "Maximum rotation rate". In such a case, the LED for the crankshaft will
not necessarily flash rapidly. It only flashes rapidly if the RPM is significantly too high, but not for
minor range violations. To perform a test, it is possible to set the parameter "Maximum rotation rate"
to the highest permitted value 20000, since the RPMs may actually be higher than expected. But later
be sure to reset the limit as low as possible for purposes of interference suppression.
If the value calculated is incorrect for the rotation speed, then the number of teeth per revolution can
be checked, or the threshold/hysteresis. This is because the module may be detecting too many signal
edges.
Ignition angle shows "---" in the display
If the rotation speed is 0 or invalid, ten it is not even possible to calculated a value for the ignition
angle. However, if the RPM value is valid, then there is a variety of possible causes. The LED for the
ignition signal must shine constant green or else the ignition signal must be checked. The LED for the
reference signal must shine constant green if an incremental counter with zero-output is used. If it
does not shine constant green, the reference signal should be checked.
If the input signals are in order, then it is worth extending the permitted ignition angle range as a test:
temporarily set a lower value for the "Minimum ignition angle". The value should be as low as
possible (see table for the description of the parameters Minimum, Maximum ignition angles). For
instance, if measuring a 4-cylinder 4-stroke engine, the difference between the two may be 180
degrees. So, if the maximum value is set to 70 degrees, the minimum may be set to -110 degrees. For
interpreting the values, note that all angles measured are brought to the range -110..+70 degrees by
adding or subtracting multiples of 180 degrees. Thus, if 77 degrees were measured, then 77-180
degrees = -10 degrees are shown. You must take this ambiguity into account.
The value for the crankshaft's zero-marking can be checked. An incorrect value there leads to an
offset of the angle display.
Ignition angle shows random numbers
The display of the ignition angle is not stable but shows apparently random numbers. If at the same
time the RPM is incorrect, then the RPM should first be checked. If the RPM is correct and stabile,
then the number of "Ignition pulses per work cycle" should be checked. Further, the settings for the
threshold value and the hysteresis of the ignition signal should be checked. When working with an
incremental counter having a zero-output, also check the reference signal.
If no Logic Level Signal is provided by the control electronics for capturing the ignition time, but it is
instead captured by a clamp ignition sensor, then the pre-conditioning of the signals as well as the
threshold value and hysteresis must be given special attention.