Automatic Measurement Selection

Selecting the individual FRF measurements to maximize the overall coherence can be a very time-consuming task. To help you and speed up this step, we have developed Automatic Measurement Selection (AMS). AMS feature selects for you the most coherent FRFs, according to the settings you define.

How to: Work with AMS

You can find AMS in the Measure module. You can only use AMS when you are doing a measurement campaign.

AMS will automatically select the best measurements, checking a metric that we call “measurement similarity”. The similarity considers the coherence of all sensor channels of one excitation location, and picks the best impacts, according to your settings.

Simply speaking, AMS finds and selects the impacts that make a column of the coherence matrix in Analyze “as green as possible”. When you apply AMS to all excitations, it will optimize the entire coherence matrix at once. In the pictures below you can see how the coherence of the entire measurement improves when using AMS.

How to: Create a AMS preset

You can create as many AMS presets as you desire and run them separately, to check the results when using different settings.

To create a new AMS preset, click  . The new AMS preset will appear at the top of the Impact location card.

How to: Choose AMS settings

By default, AMS will always select the two best-matching measurements, no matter which settings are defined. However, you can edit each setting of your AMS preset.

When creating a preset, you can edit the following settings:

• Preset name. You can rename each preset according to your liking.
• Hammer. You can specify if you want AMS to check FRFs of a single or multiple hammers, selecting them from the dropdown. By default, AMS will run for both hammers simultaneously and select at least 2 measurements per hammer.
• Frequency range. You can specify the frequency range of interest where AMS will compare the FRFs. By default, this is the entire frequency range specified in the DAQ settings. If you have multiple hammers selected, AMS will only operate within the limits of the high, low, or band-pass filters that you defined for each hammer in the DAQ settings.
• Minimum similarity. You can definite a minimum similarity threshold, as a percentage. AMS will select the most similar measurements above that predefined preset. If no measurements reach this similarity, the best 2 measurements will be selected anyway.
• Maximum valid measurements. The maximum amount of measurements AMS should select. When this is off, AMS will include all measurements that are above the minimum similarity thresholds.

You can create multiple presets according to your needs. For example, you can create a preset for each hammer you are using in the project, each of them checking similarity in a specific frequency range.

How to: Run AMS after a measurement

You can run AMS per single excitation or for the entire measurement.

To run it for a single excitation point, you have to:

1. Select the excitation from the list.
2. Click on the AMS preset button.

To apply AMS to all excitations in the project, you have to:

1. Open the AMS preset edit mode.
2. Select Run for all.

How to: Use AMS in live mode

You can also use AMS in Live mode, while you are measuring. After every impact, DIRAC will check its similarity with the others and will select the most similar ones automatically. If you are testing by yourself, you can be notified with sound feedback whether the impact meets the similarity requirement or not.

To activate the AMS live mode, double-click on the AMS preset, and it will turn orange.