About modal exciters

The input (force) measurement is a critical aspect of successful modal testing. Exciters featuring high force-to-weight ratios, specifically developed to ensure the best possible modal test performance with the fastest setup, are essential for quality experimental modal models and choosing the right one is key.

The quality of any model for experimental modal analysis is directly proportional to the quality of the frequency response functions (FRF) measured between the chosen input and output locations. Contrary to what many experimentalists think, the input (or force) measurement is one of the most critical aspects of a successful modal test.

Not only do errors originating here affect each and every FRF measurement but also, since these errors are typically ‘hidden,’ they are difficult to detect visually – which is not the case with output (or vibration) measurements.

Therefore, obtaining accurate and reliable force measurements is a significant challenge, where several issues must be considered during test setup. For a precision modal test setup in which the natural choice of excitation is one or several exciters, these issues include:

  • Choosing the best location for the exciter
  • Minimizing interaction between the exciter and the device under test (DUT)
  • Distributing and minimizing dynamic-force levels
  • Ensuring that sufficient low-frequency energy input is provided

Based upon years of practical experience in modal testing, Brüel & Kjær modal exciters, all of which feature high force-to-weight ratios, have been specifically developed to address these issues and to ensure the best possible modal test performance with the fastest setup. With sine force ratings of 100 – 1000 N (22 – 225 lbf), displacement of up to 50.8 mm (2 in), magnesium armatures with through-hole design for simplified operation with tension-wire stingers, as well as the incorporation of rare-earth magnet technology in some models, this line of robust exciters can handle even the most demanding of modal test applications. An optional built-in electrical control system for stinger pre-tensioning affords complete freedom of exciter positioning and orientation. It allows the use of superior tension-wire stinger technology without the need for external mechanical pre-tensioning.

A complete range of dedicated accessories is available to provide an unmatched degree of high-precision measurement and effortless setup. Our range includes force transducers, impedance heads, lateral exciter stands for easy horizontal positioning, as well as a selection of stingers. Also available are push-pull steel rods and various tension-wire stingers with different attachment methods, including a novel snap-on accessory for fast mounting and dismounting of push-pull rods.

The Brüel & Kjær line of modal exciters features:

  • Force ratings ranging from 100 –1000 N (22 – 225 lbf)
  • A complete line of heavy-duty, matching power amplifiers
  • Lightweight, high-rigidity moving elements made of magnesium
  • Superior force-to-weight ratios due to a unique design based on rare-earth magnet technology
  • Capacity to easily incorporate tension-wire stingers
  • Peak-to-peak displacement up to 50.8 mm (2 in) for enhanced low-frequency performance
  • A wide selection of accessories to ensure successful modal testing: push-pull rods and tension-wire stingers, trunnions, lateral exciter stands, and electrical control systems for stinger pre-tensioning.

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