In multistation operation, a basic distinction is made between synchronized and non-synchronized operation.
Synchronized multistation operation
In a multistation network, the master synchronizes all connected slaves via the ibaNet FO connection with regard to the acquisition. The following image shows the processes in synchronized operation schematically.
The multistation master specifies the date, time, and the highly accurate clock for all slaves. Ideally, all computers involved should be connected to an external, accurate time source such as a Grandmaster Clock (GMC) or an equivalent high-precision external time source in order to obtain a relatively accurate time even if the master fails. However, the respective system times are irrelevant with regard to synchronization of the acquisition on the individual slaves.
Only the date and time of the master are used for the acquisition and to time stamp the data files!
The ibaFOB card in the master generates a highly accurate clock signal in the nanosecond accuracy and feeds it into a counter value. This clock signal or running counter value is transmitted via the FO connection to the ibaFOB cards of the slaves in order to synchronize them.
Simultaneously, the counter value and the date and time from the master are distributed to the slaves via the FO synchronization connection. This synchronization mechanism sets the system time of each participating computer, ensuring a consistent time base for data acquisition across all systems.
When a trigger event occurs on one participant, a message containing the trigger name, time stamp, and counter value is sent because all participants share the same time base and counter values, the event can be accurately classified on all systems, even in the presence of transmission latency, for example over long distances.
The receiving participants take the time stamp from the message to start the corresponding data file and select the samples according to the counter reading. The start time of the data file is the time of the trigger event, offset by a pre-trigger, if configured. Nevertheless, the time stamp of the trigger event is applied to the file name, if configured in the data store.
For illustration, see also the example in chapter Trigger configuration.
Non synchronized multistation operation
In non-synchronized operation, all computers operate as independent systems. There is no synchronization via an ibaNet FO connection and therefore no master-controlled acquisition. Each participant runs its data acquisition based on its own local clock. The only interaction between participants is the exchange of trigger information when a trigger event occurs.
The following image shows the processes in non-synchronized operation schematically.
Each non-synchronized participant must therefore be explicitly configured to exchange trigger events with every other participant it is intended to communicate with. Unlike synchronized operation, no central configuration or automatic distribution of trigger connections is possible. All trigger communication relationships must be defined individually.
Only the multistation LAN is available for communication. When a trigger event occurs, the relevant participant sends a message containing the trigger name, its own clock counter reading, and its own date and time.
The receiving participants take the time stamp from the message and assign it according to their own time in order to date the data file and select the appropriate samples. The start time of the data file is the time of the trigger event, offset by a pre-trigger, if configured. Nevertheless, the time stamp of the trigger event is applied to the file name, if configured in the data store.
Accurate time synchronization is critical in non-synchronized operation. Each participant must be connected to a Grandmaster Clock (GMC) or an equivalent high-precision external time source. The timestamp provided by this time source is used to assign and align recorded data during storage and later analysis.
Note |
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To avoid conflicts between Windows time management and ibaPDA time synchronization, also disable the local Windows time service. |
Other documentation |
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Information on configuring time synchronization in ibaPDA can be found in the ibaPDA documentation, part 2 "I/O Manager." |
If a trigger event is received with significant delay and the corresponding data is no longer fully available in the receiving system’s RAM, the receiving participant will still start a recording. In such cases, the resulting data file may miss samples at the beginning. However, the trigger event itself is documented and timestamped according to the trigger information received.