Rockwell Automation 1441-PEN25-Z Enpac 2500 Data Collector - Manual (Page 288)

288 Rockwell Automation Publication GMSI10-UM002D-EN-E - August 2012
Chapter 11 FRF Frequency Response Function Extension Module
Newtons Law and Apparent
Mass Newtons 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 36 - 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 CH2
2 Hardware being tested
3 Modally tuned hammer fitted with correct tip connected to CH1
4 Foam support to allow free movement
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