--Modal Test--
 
  Test Equipment

Exciting the structure with a measured force is required for carrying out a modal test. The force can be imparted by an electromagnetic shaker or by an impulse hammer. The response of the structure is measured by accelerometers.
What is an accelerometer?
An accelerometer is a device that measures acceleration.

How does it work?
The acclerometer is a transducer commonly used in electronic sensors. The accelerometer generates a signal in accordance to the acceleration experienced by the sensor unit. The signal is then fed into a electronic circuit for processing.

Modal Hammer
The modal hammer is an impact device that excites the structure with a constant force over a frequency range of interest. The different tips determine the width of the input pulse and thus the frequency bandwidth. The harder the tip, the shorter the pulse duration and thus the higher the frequency content.

Modal Impact Hammers and Punches
  Shaker

Electromagnetic Shaker
The force is generated by an alternating current that drives a magnetic coil. The maximum frequency limit varies from approximately 5 kHz to 20 kHz depending on the size of the shaker. The size of the shaker varies with force rating. For example, the smaller the shaker, the lower the force rating.

Typical Modal Test Shaker Excitation
   

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