Crystal Instruments CoCo-80X handheld dynamic signal analyzer allows users to acquire measurements with unparalleled convenience in the field. The rugged design features a compact display for quick, easy, and accurate data recording and analysis. This powerful hardware system is now combined with Crystal Instruments patented GPS time synchronization technology, featuring a time accuracy of 100 ns. Users can now execute Operational Modal Analysis to study the dynamic characteristics of large structures such as bridges and buildings. Testing plans and 3D model geometry created in EDM Modal can be transferred onto multiple CoCo devices to acquire ambient vibration responses. GPS time stamping technology will synchronize the simultaneous measurements acquired from various handheld systems. Users can then use EDM Modal software to post-process and analyze the data to discover the modal parameters of the test structure. The robust workflow described and illustrated here provides a seamless integration of the operational modal analysis process.
Basic steps in the process are briefly highlighted below.
1. Create Geometry
The geometry model of the structure can be created or imported in EDM Modal using the simple yet powerful Geometry Editor.
The built-in component library has default models that can be edited and graphically modified. The editor table can also be used to fine-tune and obtain the desired 3D geometric model of the test structure.
2. Create Testing Plan
Testing Plan in EDM Modal allows users to create, customize, and control the flow of the testing process.
Testing Plan also provides information about the acquisition status. Users can also change or modify the parameter for each individual measurement entry.
3. Upload Testing Plan
The test plan can be uploaded to multiple CoCo devices.
4. Configure Analysis Parameters on CoCo
Various analysis parameters are configured according to the test requirements on the CoCo devices.
5. Set up Other Settings on CoCo
The input channels and trigger setup conditions are set up according to the test requirements
6. Enable Recording and GPS Functionality on CoCo
Raw time stream data for active channels on multiple CoCos is set up for recording.
The GPS functionality for multiple CoCos is enabled for time synchronization.
7. Execute measurements on CoCo
Measurements are executed on multiple CoCo devices and the raw time stream data is recorded.
8. Download Recorded Data to EDM Modal
Recorded measurements from multiple CoCos are downloaded to EDM Modal through Testing Plan.
9. Post process measurements to calculate spectrum data
The raw time stream signals are processed to calculate CPS signals between all response channels
10. Review complete data set in Modal Data Selection
The complete set of CPS signals obtained from processing the raw time data can be reviewed and compared.
The signals can be further smoothed to reduce noise.
11. Use Mode Indicator function to review spectrum data
Modes of the test structure can be identified using the various MIFs in EDM Modal.
This process assists in selecting a suitable band for the next stage of curve-fitting.
12. Curve-fit data to obtain modal parameters
The complete set of CPS signals can be curve-fit using various estimation methods to obtain the natural frequencies, damping ratios, and operational deflection shapes of the test structure.
13. Results
The MAC chart and modal parameters obtained from the OMA test of the structure are displayed in the following figures.
