Data logging without gaps

July 29, 2011 // By Jochen Neuffer, Vector Informatik
In order to simulate real situations for the communication networks in a vehicle it is necessary to perform extensive test drives in a real environment. Large amounts of data need to be acquired, recorded and, afterwards, accessed. Here is how this can be achieved.

In vehicles often different bus systems are used which significantly increases the effort for troubleshooting and analysis. In order to simulate real situations for the communication networks in a vehicle it is no longer sufficient to perform tests in the laboratory only. Therefore it is necessary to perform extensive test drives in a real environment. The test fleet is typically equipped with dedicated data loggers, the tool of choice for recording data traffic of all busses as well as selected I/O lines. So this data can accessed at any time during quality assurance tasks.

Shortly before production maturity, in-depth testing in vehicles is typically conducted in the context of test drives. To achieve the greatest possible test coverage, some of these tests are performed under extreme environmental conditions. Whether they are winter tests in Finland at -30° C, hot weather tests in Death Valley at over 50° C or week-long drives through the Brazilian rainforest at high humidity and on rough roads, in the end the vehicle and all of its components must operate smoothly. The installed data loggers must be able to withstand these harsh conditions as well. This means that they must be mechanically rugged and operate reliably over a broad range of temperatures.

Various bus systems are used in motor vehicles or commercial vehicles: CAN, LIN and FlexRay. One technical requirement is that the data of all of these buses needs to be logged simultaneously, i.e. time synchronously. The logger must not influence the bus traffic here; it may only observe it. Since the loggers are often permanently installed in test fleet vehicles, and a test series may take several weeks, they must exhibit very low current draw in their quiescent states – another requirement of data loggers. Furthermore, the devices must be ready for operation as quickly as possible, so that the first occurring message can be logged too.

Not only are the loggers typically permanently

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