Determine Noise Floor

March 29, 2018

A good starting point for preventative maintenance is determining the noise floor of a shaker during acceptance, validation, and installation.

With this data, test engineers can determine if there are any issues with ground loops or other environmental noise sources. Additionally, engineers can evaluate tests near or at the level of the background noise. From there, they can determine if the test is possible to run or if there might be problems based on the specified frequency range and amplitude.

The noise floor of a shaker can be determined by adjusting the following:

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

Taking Noise Floor Measurements

To take noise floor measurements, prepare (but don’t run) the system. The steps are as follows:

  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 performed in the VibrationVIEW software with System Check. This measurement will be the best measurement from your shaker. From this information, you can determine the environmental baseline and make recommendations to minimize 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. You can also prepare the system in the configuration you intend to test (with a head expander and/or fixtures, etc.) The point is to determine the noise floor of the system as a baseline for future preventative maintenance. 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 every laboratory’s preventative maintenance program.