everything that rotates
                        needs to be balanced


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Vibration Information for rotating machinery applications.


Transducer Mounting

Friday, June 10, 2011

A transducer can be mounted in different ways. The way it is mounted can affect the frequency output. Each transducer is calibrated and its frequency response chart is supplied by the transducer manufacturer. The chart shows how linear the output is for a specific input. For example, 10g input across the entire frequency range should yield a linear level of 10g output. At some frequency, the response is not linear. The frequencies outside linear region is not accurate in amplitude. The linear frequency response is the frequency ranges of the transducer (Please see Frequency Response Figure).

Although a good sensor may have linear frequency response up to 30,000 Hz, the way it is mounted will greatly affect that range. Each mounting method has its own resonance issues, which magnify the vibration amplitude that occurs in that range. Resonance is shown in Frequency Response Figure as a high peak. Good transducers should have linear response ranges within  ± 5%. Differences greater than that are typically not acceptable.

There are different types of transducer mounting: probe tip, magnet, adhesive, and stud. Probe tip mounting has the narrowest linear frequency range. The vibration usually begins to be amplified in the range of 500 Hz. Magnet and adhesive mounting give wider range up to 1,000 Hz to 5,000 Hz. Stud mounting has the widest range up to 10,000 Hz or higher.

It is very important to understand the frequency response of a transducer. It will greatly affect the frequencies of interest. For example: If frequencies of interest are in the range of 500 Hz, we do not want to use a probe tip mounting since it amplifies the vibration in that range. Other mounting methods are preferred such as magnet mounting or adhesive mounting.

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