Dynamix UM-S User Manual download pdf (Page 16)

16 Rockwell Automation Publication 1441-UM003A-EN-P - May 2011

Chapter 2 FRF Frequency Response Function Extension Module

Newton’s Law and

Apparent Mass

Newton’s Law states that force equals mass x acceleration:

F = ma

Rearranging this gives:

m = F/a

The units for this are N/m/s2. The definition of a Newton:

N = kg x m/s2

So we can see that:

N/m/s2 = kg

Setting Up an FRF

Measurement

When setting up an FRF measurement, first set up the test hardware before you

configure the parameters for the FRF Module.

Figure 1 - Example FRF Measurement Setup

Test Hardware Setup

When setting an FRF test, you need this equipment:

• Accelerometer

• Hammer

• Object whose FRF measurement you are collecting

• Support for the object that provides free movement when the object is

struck with the hammer, for example, as a foam support

32159-M

1 Accelerometer connected to connector B

2 Hardware being tested

3 Modally tuned hammer fitted with correct tip connected to connector A

4 Foam support to allow free movement

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Dynamix UM-S User Manual Page 16