No matter how many catalogs you peruse, sales pitches you endure or product demonstrations you attend, selecting the right vibration test equipment for your application can be a challenging assignment. Should you purchase a complete turnkey vibration test system or buy the individual components–the controller, the amplifier, the shaker, the software–and assemble the system yourself? Well, it depends–depends on your company’s business practices, core competencies and business practices, and your own expertise.
Finding the system that is both configured for your needs and easy to use requires a thorough investigation of the available equipment. Vibration test systems often are configured for each application and customized for each user, said John Raymond of Unholtz-Dickie. The manufacturer must know your application to help you find the best fit.
It is misleading if a system is simple and easy to use but offers few choices, is intuitive but does not perform in a manner you need, said Susan Brooksbank of Data Physics Corp. For example, if your test requires 100 breakpoints and your system offers only five, your job is actually much more difficult.
You can be misled by looking only at the specifications, because some ratings are applicable for special operating conditions, added Mr. Raymond. Looking just at specifications does not tell you how the equipment will perform for your particular application. For best results, look deeper to see under what conditions the specifications apply.
After researching the appropriate equipment, the next step is to find the products that will make the job easier. But what are the functions that can make your job easier?
A turnkey, customized vibration system including fixturing and test-data management capabilities is one option sure to meet your needs. Many companies offer a service to analyze your requirements and provide all the hardware and software needed to complete the task quickly and easily.
At the other extreme, to configure your own system, it is best to work closely with various equipment vendors because they have the experience and expertise to help you choose the appropriate products. The amplifier, for example, is an essential component that provides power to the vibrator’s armature coil. But how do you know if your amplifier is supplying the appropriate amount of power?
One way is to specify equipment that continuously monitors the operating conditions of the amplifier and vibration components. This would allow you to check for proper system operation and correct malfunctions without leaving the control room.
Fixtures are important for keeping products securely connected to the table. They facilitate the mechanical coupling of a test item with the shaker. Magnesium is the material most often selected because it is lightweight yet provides a more rigid fixture. The more rigid the fixture, the better the performance.
The vibration controller ensures that the shaker performs as programmed and monitors the results of the product on the table. Enhancements such as safety controls, automated tests, analysis display and test integration are important features to look for, said Nitin Shroff of GenRad. Superior controllers provide signal-processing hardware to attain shorter test-loop times and allow quick adaptation of tests to the application.
The choice of a shaker is determined by many aspects, such as product type, size and application. Shaker types include the inexpensive mechanical type; the versatile electromagnetic unit; and the hydraulic version, which offers a longer stroke displacement.
The checklist for shakers should include the payload limit, multiple operation capabilities (including the number of movement axes), and the capability for sine, random and shock tests. Cooling, safety, suspension and isolation also must be verified.
The right software can help make your job easier. A menu-driven program, a graphical interface and an intuitive layout of parameters help you navigate easily and quickly through test programs. The capability to automatically store test parameters and store data with the appropriate test parameters is also useful.
You must be able to visualize the data during and after a test, observed Ms. Brooksbank. If a system is configured with 16 control and measurement channels, you should be able to see all 16 channels.
Custom report generation and a comprehensive test data- handling capability are important system requirements. The report could include information on job cost, work flow and control; project scheduling, maintenance of calibration records, and storage of commonly used specifications.
Look for the most cost-effective implementation and integration of your testing needs, said Richard McCormick, President of MB Dynamics. Equipment is only part of the equation. Applications, information, education and consultation are your principal sources of value.
Copyright 1995 Nelson Publishing Inc.
January 1995
