How to Set Up a Snapshot Logger

This guide outlines the process of configuring an event-based data logger to capture snapshots. It covers setting up triggers based on conditions or using a software button for manual operation.

Sections

1. Snapshot logger with a trigger variable

2. Snapshot logger with a dashboard button

3. Case example: peak-valley logging triggered by a Moog system

Snapshot logger with a trigger variable

1. Create a new logger on the controller or in the GI.bench project. Select the variables to be added to the logger, give the logger a unique name, and select Event based from the Logger type drop-down list.

   

2. Set the Event length to 1 data sets. This means that for each event one sample for all selected variables will be added to the data file. Set the File length to the number of events that should include in one data file. For example, if the File length is set to 100 events then for each variable 100 samples will be added into one data file. After 100 events have passed a new data file will be created for the next 100 events.

3. In the Trigger tab setup an Event trigger function, for example when a digital input variable > 0.5. Leave the Mode at Single slope. This setting specifies that the variable must reset to 0 before the trigger condition is re-enabled.

4. In the Storage tab, configure the desired file format for the data file, such as binary UDBF or CSV. By default, the logger files are saved in 'C:\Users\Public\Documents\Gantner Instruments\GI.bench\data\records\'.

5. In the Enhanced settings set Init state to Single shot enabled. This means that the logger is automatically enabled after starting data acquisition. No manual action is required.
   

6. Save the GI.bench project and switch to the Data acquisition tab in GI.bench to activate the snapshot logger. The snapshot logger status shows 'armed', meaning it is ready to receive the trigger to take a snapshot.

   

Snapshot logger with a dashboard button

1. 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.
2. 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.

   

3. In the dashboard, add a Button (SingleStat element) and assign the virtual setpoint variable to the button. In the element settings, ensure that Mouseup is set to 0 and Mousedown is set to 1. Optionally, enter text to display on the button.

   

4. Every time you press the button, the virtual variable changes to 1, triggering the addition of a new data set (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 tests. It aims to condense time history data into a sequence of peak (tensile) and valley (compressive) data points, thereby minimizing the volume of data stored on disk.

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 file each time the STEP% variable reaches 100%.

Event-based logger configuration

Follow the steps explained in section Snapshot logger with a trigger variable 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)