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Determine Noise Floor

March 29, 2018

A good starting point for Preventative Maintenance (PM) is determining the noise floor of your shaker during acceptance/validation/installation.

Possession of this data will enable test engineers to determine whether there are any issues with ground loops or other environmental noise sources. Decisions can also be made about tests which may be in the level of the background noise and whether they are possible to run, or if there might be problems based on the specified frequency range and amplitude.

The noise floor of your shaker can be determined by varying the following :

  • Blower on/off
  • Amplifier on/off
  • Gain at reset, 25%, 50%, 75%, and 100%.

To take noise floor measurements, prepare (but don’t run) the system. Follow the steps below:

  1. With the blower OFF, amplifier OFF, and gain in the RESET position, take a measurement of the input signal amplitude and frequency using the acceleration waveform and acceleration spectrum graphs of your vibration controller. (This is done in VR’s VibrationVIEW software with System Check). This is going to be the best your shaker will ever be able to do. You can see the environmental baseline and make recommendations on facility changes to minimize the noise.
  2. With the blower ON, amplifier OFF, and gain in the RESET position, take a measurement of the input signal amplitude and frequency
  3. With the blower ON, amplifier ON, and gain in the RESET position, take a measurement of the input signal amplitude and frequency
  4. With the blower ON, amplifier ON, and gain at 25%, take a measurement of the input signal amplitude and frequency.
  5. With the blower ON, amplifier ON, and gain at 50%, take a measurement of the input signal amplitude and frequency.
  6. With the blower ON, amplifier ON, and gain at 75%, take a measurement of the input signal amplitude and frequency.
  7. With the blower ON, amplifier ON, and gain at 100%, take a measurement of the input signal amplitude and frequency.

You can prepare the system on a bare table with an accelerometer on the shaker head or armature, or you can prepare the system in the configuration you intend to test (with head expander and/or fixtures, etc). The point is to determine the noise floor of the system as a baseline for future PM. Your initial recording will be used as a benchmark and compared against all future recordings.

Regularly scheduled shaker validation, including noise floor recordings, should be part of a every laboratory’s PM program.