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January 29, 2009
IMAC XXVII Papers and Presentations

The Modal Shop, Inc. is supporting several technical presentations at the upcoming IMAC (International Modal Analysis Conference) in Orlando on Feb 8th  through Feb 12th – click here for additional conference information.  Here is a brief schedule of our presentations.  For any further requests, please fell free to contact us at

Session 02 | Acoustics/Transducers
(Monday Morning around 11:00a)
277 - Improved Low Frequency Accelerometer Calibration
M.I. Schiefer, R.W. Bono, The Modal Shop, Inc.; R.D. Sill, PCB Piezotronics, Inc.

This paper will discuss a newly developed implementation of low frequency accelerometer calibrations. The goal is an improved low frequency accelerometer calibration system capable of performing quality measurements with low uncertainties while maintaining good throughput and the simplicity of traditional back-to-back calibration techniques. By using an optical encoder as the measurement reference instead of a traditional reference accelerometer, limitations due to shaker stroke length are nearly eliminated, with the practical limitation for a quality calibration measurement at ultra low frequency being the resolution of the sensor under test itself.

Session 07 | Experimental Techniques
(Monday Afternoon 4:00p)
197 - Shaker/Stinger Effects on Measured Frequency Response Functions
D. Cloutier, P. Avitabile, University of Massachusetts, Lowell; R.W. Bono, M. Peres, The Modal Shop, Inc.

Shaker testing is utilized in the development of many experimental modal tests. The setup of the shaker, stinger and transducers can cause difficulties that are often misunderstood. Many times incorrect measurements are obtained and the test engineer may not realize that the measurements are not appropriate.
This paper overviews some of the common problems that are typically encountered. Measurements are made on several structures to better understand some of the common problems observed. These include shaker alignment, stinger arrangement, reciprocity, impedance head difficulties and many other common issues that must be clearly understood in order to make the best possible overall measurements.

Session 19D | Tutorial on Sensors and Instrumentation II
(Tuesday Afternoon 1:30p)
321 - One Hour Tutorial Guidance for Measuring Mechanical Shock and Vibration
P.L. Walter, Texas Christian University

After first clarifying some of the reasons that we measure mechanical shock and vibration, basic requirements are provided for all measurement systems that process these signals. High-frequency and low-frequency dynamic models for the measuring accelerometer are presented and justified. These models are then used to investigate accelerometer responses to mechanical shock and vibration. The results enable “rules of thumb” to be developed for data assessment and accelerometer selection. Other helpful considerations for measuring mechanical shock and vibration are also provided

Session 19D | Tutorial on Sensors and Instrumentation II
(Tuesday Afternoon 2:30p)
322  - Decoding an Accelerometer Specification Sheet – What Sensor Manufacturer’s Don’t Tell You
D. Lally, PCB Piezotronics

Comparing apples to apples isn’t always as easy as it seems… different sensors, different vendors, and different meanings.  Let’s sort it out – A review of noise specifications, transverse resonance, linearity calculations, hermetic sealing, and other issues

Session 19D | Tutorial on Sensors and Instrumentation II
(Tuesday Afternoon 3:00p)
337 - One Hour Tutorial Current Status of IEEE 1451.4
M.I. Schiefer, The Modal Shop, Inc.

Overview and summary of 1451.4 (TEDS) standard. A review of the current vendor offerings and status

Session 19D | Tutorial on Sensors and Instrumentation II
(Tuesday Afternoon 4:00p)
327 - Rigid Body Property Testing Using 6DOF Force Transducers
R.W. Bono, The Modal Shop, Inc.; D. Brown, University of Cincinnati

Discussion of new methodology for measuring the rigid body properties of a test structure.  The technique involves multi-dof force transducers and an array of accelerometers

Session 31F | Tutorial on Sensors and Instrumentation IV
(Wednesday Afternoon 3:30p)
335 - One Hour Tutorial Practical Considerations of Shaker Excitation Thechniques for Modal Analysis
M.A. Peres, The Modal Shop, Inc.; P. Avitabile, University of Massachusetts, Lowell

Discussion includes the benefits and limitations of the variety of common shaker excitation techniques. Types of methodologies include various random, burst random, periodic and sinusoid techniques as applied to different test structures, boundary conditions and digital signal processing considerations