This article outlines the process of configuring an event-based data logger to capture snapshots.
Sections
Snapshot logger with a trigger variable
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Create a new logger on the controller or within the GI.bench project. Select the variables to include in the logger, assign a unique name, and choose Event-based from the Logger type drop-down list.
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Set the Event Length to 1 dataset. This means that for each event, one sample of all selected variables will be added to the data file.
Set the File Length to the number of events to be included in a single data file. For example, if the File Length is set to 100 events, then 100 samples per variable will be stored in one data file. Once 100 events have occurred, a new data file will be created for the next 100 events.
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In the Trigger tab, set up an Event Trigger function, for example, when a digital input variable > 0.5. Leave the Mode set to Single Slope. This ensures that the variable must reset to 0 before the trigger condition can be re-enabled.
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In the Storage tab, select the desired file format for the data file, such as binary UDBF or CSV. By default, logger files are saved in:
C:\Users\Public\Documents\Gantner Instruments\GI.bench\data\records. -
In the Enhanced Settings, set Init State to Enabled. This ensures that the logger is automatically activated when data acquisition starts, requiring no manual action.
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Save the GI.bench project and switch to the Data Acquisition tab to activate the snapshot logger. The snapshot logger status will show "armed", indicating that it is ready to receive a trigger to take a snapshot.
If you have completed your measurement but the latest logger file has not reached the specified file length (e.g., 100 datasets), it remains a temporary file. To close the temporary file, manually stop the logger.
Snapshot logger with a dashboard button
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Add a virtual setpoint variable on the controller. Give the variable a name and write the configuration to the controller. Ensure that this setpoint variable is included in the project's system stream.
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Follow the steps explained in the above section to create an event-based logger. Use the virtual setpoint variable as the event trigger. Since we will use this setpoint variable as a on/off switch (Boolean), set the trigger condition to > 0.5.
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In the dashboard, add a Button (SingleStat element) and assign the virtual setpoint variable to the button. In the variable conditions settings, ensure that Mouseup is set to 0 and Mousedown is set to 1. Optionally, enter text to display on the button.
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Each time you press the button, the virtual variable changes to 1, triggering the addition of a new dataset (snapshot) to the logger file.
Case example: peak-valley logging triggered by a Moog system
Snapshot logging, also known as peak-valley logging, is a data reduction technique commonly used in aerospace fatigue and endurance testing. It condenses time history data into a sequence of peak (tensile) and valley (compressive) data points, reducing the amount of stored data while preserving essential information.
Using the Ethernet communication interface between the Q.series DAQ system and the Moog Aerospace Test Controller, peak-valley data logging can be configured in GI.bench.
Theory of operation
The Moog Aerospace Test Controller can send a STEP% variable over Ethernet to the Q.station controller. The STEP% variable ramps from 0% to 100% for each instruction step of the loading spectrum. When the instruction step reaches its endpoint, the STEP% variable equals 100%. In other words, the STEP% variable reaches 100% at each peak or valley of the loading spectrum.
Using an event-based logger in GI.bench, a snapshot can be written to the file each time the STEP% variable reaches 100%.
Event-based logger configuration
Follow the steps explained in the Snapshot logger with a trigger variable section to create an event-based logger. Use the Shared Memory channel from the Moog system that contains the STEP% variable as the event trigger. Set the trigger condition to == 100.
Example of peak-valley data file (*.CSV format)
