Extract data from vehicle networks

Every over-the-road vehicle sold today contains at least one network-based electronic control unit (ECU) that provides the measured parameters on the vehicle's embedded network. You can use those parameters in conjunction with data from sensors such as thermocouples and accelerometers in automotive tests.

Use data from your own sensors in conjunction with data that a vehicle produces to perform tests.

Many ECUs periodically provide vehicle parameters for all interested network nodes. Some ECUs broadcast data only when another node requests the data. For example, the network PCM typically broadcasts RPM and vehicle speed data. The instrument cluster looks for these messages and updates its gauges. Networks such as SAE J1850VPW update RPM at rates around 10 Hz. Vehicles equipped with the Controller Area Network (CAN) bus get RPM update rates at 100 Hz. (For detailed information about the CAN bus, visit www.can.bosch.com.)

In a vehicle test, attach thermocouples to an engine or accelerometers to a vehicle's frame or body. Connect them to a data-acquisition system and time-correlate the measurements to the vehicle's speed, RPM, load, and throttle position data available through the vehicle's network.

Save the data and timestamp each measurement. Then move the data to a spreadsheet, a plotting software package, or a math package for graphing and analysis.