DAWN: Data Acquisition With In-Vehicle Networks
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HEM Data eNews

Acquiring In-Vehicle Network Data Is Easy with the Right Tools
DAWN
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SNAP MASTER
Rick Walter Welcome to the first edition of HEM Data eNews, bringing you in-depth perspectives on the aspects, challenges, and vast applications of data acquisition and analysis.

As a leading provider of targeted software and hardware solutions, as well as presenting the SAE seminar Acquiring and Analyzing Data from Sensors & In-Vehicle Networks, HEM Data has a unique and in-depth perspective on this multi-faceted industry. Every two weeks, we’ll explore the latest trends, challenges, and applications of data acquisition and analysis – as well as solutions to meet industry needs.

In this edition, we’ll start by addressing the benefits and challenges of acquiring data from the in-vehicle network compared to the traditional way of acquiring data directly from sensors.

Historically, engineers and technicians needed to mount their own sensors on a vehicle to test it. But today’s vehicles are built with many of the required sensors – making additional sensor mounting redundant and a drag on productivity. While tapping into the pre-existing sensor system saves time and energy, the user needs to be aware of the differences, complications, and limitations of using the in-vehicle network as the source of data.

When measuring data directly from sensors, the parametric data is always there and there are typically no time delays in the measurements. The data can be acquired at whatever sample rate is needed. In contrast, when acquiring network data the results are coded values that are buried inside a cryptic message. There can be significant & unpredictable delays, as your requests for data are designated as the lowest priority on the network.

Whether we are acquiring data directly from sensors or from the network, we need to define the units, labels, zero offset, scaling factor, minimum value, and maximum value.

For network data, there are additional considerations: Do we need to request the data, and if so, how? How do we find responses to our requests? How do we know who sent the message, where the data is within the message, what type of data we are collecting, and which test mode to use for that type of data?

The bottom line is this: A data acquisition user wants to acquire network data as easily as from direct sensors. To accomplish this, we need to think in terms of engineering parameters and be isolated from network messaging details.

To see how HEM Data addresses these issues, click here.

For information on HEM Data’s next SAE seminar on this subject (June 8-9, 2009), click here.

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