Applications In EMC Testing

What Suits A Diagnosis Tool For EMC Testing?

A diagnosis tool for an automotive ECU should feature some special qualities to make EMC testing easier.
  • Access to all analog values and states that are processed in the ECU
    If you are testing an automotive motor ECU you shurely would monitor the speed of the crankshaft, and if you are testing an alternator ECU you would monitor the battery voltage. Those are things we take for granted, of course.

    But what is about all the other signals, that seem to be non-essential at the first look? Signals like an error counter or the output state of a power driver? On searching for a weak point in an ECU you might find these signals very helpful. So, having complete access to an ECU means: one could do his job faster and save time and money.
  • Monitoring of the raw measurings (i.e. without software filtering)
    A proper judging of EMC impacts is only possible, if the signal could be monitored without any (software) filtering. When monitoring these unfiltered values one could learn something about the way of influence. This means, whether there are sporadic spikes, modulation effects or a DC drift.
  • Graphic display of the monitored signals
    A picture tells more than thousand words! In other words: It is much easier to analyse influences, if you see what is happening. By that meaning an on-line graphic display is a grateful benefit not only for EMC testing.
  • Peak-hold of the acquired data
    Also a fast diagnosis tool won´t become a real-time tool. That means: only a fraction of the data that is acquired in an ECU could be actual monitored - the other data would be lost. But these missing milliseconds could comprise the decidingly event, eg a crash detection and the firing of an airbag.

    A good way to solve this problem is to extract a minimum value and a maximum value already in the ECU. These values are generated in every read cycle. So, instead of eg 100 actual values only the minimium and the maximum value need to be transmitted to the diagnosis tool.
  • Sufficient fast updating of the monitored data
    If the monitoring is updated fast enough it is possible to draw conclusions about the origin of an EMC interference. So, there could be determined whether an interference only occurs sporadically, if there is a DC offset or if there are influences due to the modulation of the RF field.

    For this there should be aspired at least 10 updates per second. A faster update rate is better. For instance, with 500 updates per second one could make out a modulation frequency of 60 Hz very well.
  • Quasi-parallel monitoring of several values
    Meanwhile, in modern automotive ECUs there have to be supervised 100 measurings or more during the EMC test. To keep the checking of these values manageable there should be supervised as many measurings as possible at the same time.

    Based on what is known of pratical experience a monitoring of 30% to 50% of the total signals at the same time is fine. That could be eg 50 signals at the same time.
  • Communication interfaces to other software
    A highly-effective diagnosis tool should be designed to communicate with an other software, such as an EMC control software or also applications for environmental testing, etc.. There are various simple ways for communication, such as the serial interface (RS232),the clipboard, a DLL or the environment variables.

    The advantage is: an influenced signal could be connected to the EMC data, i.e. frequency and fieldstrength. In environmental testing the ECU data could be connected to temperature, humidity, etc..

    This communication interface is the key for the automated measuring of EMC characteristics (i.e., influences), too.

Back to the calling page