All Software Features

Modal Testing

Identify a structure’s response to excitation with modal analysis. The Modal Testing software collects responses, calculates averages, and generates transfer functions. From there, export the data to a modal analysis software.

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Capture Modal Data

The ObserVIEW Modal Testing software is compatible with a modal impact hammer for excitation. The ObserVR1000 records the impulse via the hammer’s force sensor and the structure’s output via the response accelerometers. It can capture data using the roving hammer or roving accelerometer method.

Modal test settings and data in the ObserVIEW software.

ObserVIEW also employs automatic double-hit detection. If there is a second peak in the input that is a certain percentage of the main peak value, it is considered a double hit and rejected automatically. The user defines the percentage value per their own requirements.

Advanced Feature

The Modal Testing software in version 2023.1 and later includes an advanced project type that allows the user to define the number of response and reference locations and select different response locations/directions for each reference. The user can collect fewer responses and generate mode shapes quicker with the ease of roving the hammer.

Identify Resonant Frequencies

Engineers seek to understand a structure’s natural vibration frequencies and its response to excitation. If an external vibration aligns with the structure’s natural vibration, resonance will occur. If unaccounted for, the natural vibration will be amplified and result in structural fatigue or damage.

When a structure is excited at its natural frequency, the resulting vibration creates different mode shapes that help describe the vibration.

modal testing setup with impact hammer and ObserVR1000

Modal Test Setup

Modal analysis can be experimental or operational. Engineers most often use experimental analysis, where a mechanical device excites the structure, and the response is recorded.

A modal test setup includes a device to generate the excitation, transducer(s), and a data acquisition system. The structure is subject to an impact, the transducers attached to the structure record the response, and the output signal is sent to a dynamic signal analyzer such as the ObserVR1000.

Record Responses & More

Capture transient events with an ObserVIEW/ObserVR1000 system, and access a comprehensive suite of features for additional data recording, editing, and analysis.

ObserVR1000 thumbnail



Modal Testing in ObserVIEW

In ObserVIEW, the Modal Testing software collects responses to excitation with an impact hammer. The program calculates an average response for each hit location and generates a smooth transfer function (FRF). From there, the data can be exported to a modal software such as MEscope for further analysis.

ObserVIEW reads RPC® and RSP time waveform files and supports pasted traces. Organized transfer function data are exported to a UFF or another modal data format.

With Modal Testing in ObserVIEW:

  • Manage table of hits per location and review hits
  • Average multiple data acquisitions
  • Calculate decay rate from transient ring-down events
  • Manage the acquisition channel using a large, interactive display
  • And more

Assess the Stability of a System

Add a Nyquist plot to view transfer function data as a scatter plot.

Nyquist plot of experimental data

Generate an FRF

transfer function in modal testing software

For a linear and time-invariant system, a transfer function defines some ratio of the input force and output response over a set frequency range. Frequency response functions are complex transfer functions with real and imaginary parts, which can be represented by the structure’s magnitude and phase response.

Engineers use the FRF to identify the frequencies most sensitive to excitation. These dominant frequencies are the basis of the structure’s individual modes.

Defining Modal Parameters

An experimental modal project calls for several parameters that the engineer can configure ahead of time or modify after they have created the project.

The configure trigger dialog in the ObserVIEW modal testing software.

Vibration Research found that the standard approach to defining modal parameters was time-consuming, particularly for those running basic modal tests. Rather than manually fine-tuning the parameters, the engineer can define those that represent the test’s purpose, such as maximum frequency of interest, oversample factor, and analysis duration. Learn more.

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