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Determine Noise Floor

March 29, 2018

Back to: Preventative Maintenance

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, they can evaluate tests at or near the background noise level. From there, they can determine if the test is feasible or if there might be problems at 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%

Measuring Noise Floor

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, measure 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. With 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, measure the input signal amplitude and frequency.
  3. With the blower ON, amplifier ON, and gain in the RESET position, measure the input signal amplitude and frequency.
  4. With the blower ON and amplifier ON, measure the input signal amplitude and frequency with the gain at 25%, 50%, 75%, and 100% (4 measurements total).

You can prepare the system on a bare table with an accelerometer on the shaker head or armature. You can also use the test configuration (with a head expander and/or fixtures, etc.) The point is to determine the system’s noise floor for a baseline for future preventative maintenance. Your initial recordings will be a benchmark used to compare against future recordings.

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