Agilent Technologies Agilent 35670A manual AGILENT 35670A Supplemental Operator’s Guide

AGILENT 35670A

Supplemental Operator’s Guide

Section 12 : Hammer Test Setup Without a Force Transducer

Hammer testing for modal analysis without a force transducer can yield usable results if an accelerometer is placed on the hammer and used to trigger the measurement. Although frequency response functions acquired with this technique will be affected by the dynamic characteristics of the hammer assembly and also its mass-loading effects, approximate mode frequencies and mode shapes can still be computed using modal analysis software.

On the other hand, power spectra obtained by measuring the single-channel response to a non-instrumented hammer strike may also provide information regarding modal frequencies and shapes, but success is too dependent on the consistency of the hammer strike, and therefore this technique is not recommended.

Setting Up the Hammer Test Without a Force Transducer

Attach an accelerometer to the hammer using cement or wax, and connect this transducer to Channel 1. Attach the response accelerometer to the desired location on the structure, and connect it to Channel 2. Preset the analyzer and set up transducer parameters as described in the section “Measuring with Transducers.” Then proceed with the test in accordance with the proceeding section on “Modal Testing with a Hammer and Accelerometer.”

Avg	Type: RMS	Number: 5
[FFT]	Update Rt: 5	Overlap: 0 %

Date: 10-02-96 Time: 09:24:00 PM
A: Freq Resp2/1	X:656	Hz			Y:444.409
1
e+3
LogMag
5
decades
10
e-3
0Hz			AVG:	5	3.2kHz
B: Coherence2/1	X:656	Hz			Y:939.573 e-3
1
Real
100
e-3
/div
0
0Hz			AVG:	5	3.2kHz

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