Timing is an immensely important and difficult matter in distributed multi sensor systems.

From the created signal to the storage, the data package with the measured values passes through several software blocks and systems, such as measurement adapters or Ethernet switches. In the process, propagation and transmission delays (e.g. store and forward) and process-related clock jitter occur.

Due to these phenomena, the collected measurement data will not arrive and be processed chronologically with respect to their origin at the data recorder unit, which is responsible for recording and storage.

However, an exact temporal correlation of the data packets forms the basis for a meaningful fusion of sensor values. Without it, the values are not correctly assigned and cannot represent a system in its complete model. A reliable and safe statement beyond one measured value is therefore not possible.

Clock synchronization and time stamps as a solution

To compensate for the effects mentioned above, it is important to time stamp each data package with the creation time in order to be able to assign it later. The timestamp has to be applied to the data package as early as possible in order to be able to consider transmission delays at the same time.

Taking the individual time stamps and the underlying time into account, the clocks in the complete system must run on a time basis and be continuously synchronized to form a time domain.

This forms the basis for demanding safety-critical applications and provides the basis for safety certification of this multi sensor system.