Mixed Mode Vibration Testing

Sine-on-Random (SoR) & Random-on-Random (RoR)

  • Sweeping Modes: sine tones can either be individually configured with sweeping speeds and schedules (Free Sweep mode), or jointly defined as harmonics of the first primary tone (Harmonic mode)

  • Number of Sine Tones (SoR): 1 - 12 in free-sweeping mode; 1 - 20 in harmonic mode, up to 32 when RoR is disabled

  • Number of Bands (RoR): 1 - 12, up to 32 when SoR is disabled.

  • Operation Controls (SoR): Tone On and Tone Off controlled by run schedule, external events, or user commands

  • Operation Controls (RoR): Band On and Band Off controlled by run schedule, external events or user commands

  • Supports up to 512 input channels

Mixed Mode Random Vibration Testing

Some vibration environments are characterized by quasi-periodic excitation from reciprocating or rotating machines (e.g. rotor blades, propellers, or pistons). These can be simulated as one or more high-level narrowband or sinusoidal vibration components superimposed on a low-level broadband random profile. These are called mixed-mode random tests.

There are two types of mixed-mode random tests supported in EDM: Sine on Random (SoR) and Random on Random (RoR). In each of these test types, an additional vibration profile is placed on top of the regular broadband random profile. In Sine on Random, this additional profile consists of one or more sine tones that sweep through a specified frequency range. The random profile may represent a base excitation or background noise level, and the sine tones represent strong single-frequency excitations.

A typical profile of SoR described in MIL-STD-810F is shown below. Note that the random broadband profile is defined in units of Power Spectral Density, or g2/Hz, while the sine components are specified as amplitudes in units of g.




When SoR is running, the sine tone or tones are shown superimposed on the broadband random profile:



Up to 32 sine tones can be placed on top of the random profile. Up to 20 sine tones are available if both Sine on Random and Random and Random options are enabled when creating the test.

A Random on Random (RoR) test superposes one or more high-level narrowband random profiles on top of the broadband random test profile. These narrowband profiles can be swept through a specified frequency range.

When RoR is running, the random narrowband profiles are shown superimposed on the broadband random profile.



Continuous Data Recording

During vibration control, all measurement input and drive signals can continuously record to a Spider-NAS or the internal storage residing in each front-end. Users can view and analyze data files with Crystal Instruments Post Analyzer. The variable sampling rate can be enabled to simultaneously record slow-change signals together with high speed vibration data.

Vibration Utilities App

Crystal Instruments in partnership with our sister shaker company Sentek Dynamics provides users with the Vibration Utilities mobile app on iOS and Android. This app provides calculation features for sizing your vibration profile (Random, Sine or Shock) and searches through our catalogue of shakers and controllers for the best fit.



Multi-Resolution Feature

The Spider controller's unique Multi-Resolution feature is a perfect solution for displaying low frequency sine tones that are hard to display due to an inadequate frequency resolution.

Traditionally, providing a better resolution for low frequency sine tones required increasing the block size (also known as "frame size"), resulting in more data collection time and slower reactions to hitting abort limits.

On the other hand, Multi-Resolution applies a custom 8x sharper resolution to only the low frequency part of the spectrum, while running the rest of the spectrum with the original resolution.

SoR profile (MIL-STD-810H) without and with Multi-Resolution

Drive Notching/Limiting for Random

Limiting is applied to control or monitor channels. Three types of limiting are available in Random Control: frequency domain, time domain, and advanced limit. Frequency domain limiting is spectrum limiting. Limit types are notching limit, abort limit, and alarm limit.

Time domain limiting compares raw data or the RMS value of input channels to the high limit. The occurrence of exceeding the high limit is one of the system events to which desirable actions can be added.

Advanced limit includes summed channel notching and vector notching. A summed virtual channel is defined as the weighted average of raw time stream signals from multiple input channels. The notch profile of a summed channel is defined in the frequency domain.

A vector RRS signal is defined as the vector sum of raw time stream signals from 3 input channels. The notch profile of a vector RRS signal is defined in the frequency domain as well.

Supports up to 128 notching/limiting channels out of 512 input channels.

Vibration Testing Hardware

Related Vibration Testing Software Options

Monitoring Through EDM Cloud

All vibration tests in EDM-VCS support status checks through EDM Cloud. With EDM Cloud support, users can set up any VCS test to upload live data or run logs for completed tests to a cloud storage space provided by Crystal Instruments, where data is securely stored in the user’s account.

The EDM Cloud website is located at https://cloud.go-ci.com. Users can access EDM Cloud from anywhere in the world to check the status of past and current tests. A secure login flow ensures the status can only be checked by authorized personnel with proper credentials. Multiple logins for accessing the same Cloud account is available.

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