SHAKER VIBRATION TESTING

shaker under test

Quality is the watchword of modern manufacturers and testing feedback is the way they achieve it. Vibration testing on electrodynamic or hydraulic vertical shakers (and on shaker-driven horizontal slip tables) is done for a broad range of reasons. These include demonstration of compliance with standards, new design qualification, stress screening, fatigue life evaluation, shock and earthquake survivability demonstration and various product pre-shipment audit and burn-in tests. Automotive, aerospace, avionic, telephonic, consumer electronic and military equipment providers use shakers to prove and sustain the quality of their wares. Shakers are used to subject a Device Under Test (DUT) to random, swept-sine and transient shocks.

A controller (more properly a Vibration Control System or VCS) is required to force the moving shaker table to impose the desired acceleration profile to the DUT. Crystal Instruments offers a broad range of VCS, offering more models than any other manufacturer. Our fourth-generation hardware is absolutely state-of-the-art; employing fast floating-point DSPs, our patent-protected dual-ADC input circuitry providing 150 dB dynamic range (simultaneously discerning ±600 nV in the presence of ±20 Volt) and robust IEEE 1588v2 Ethernet® communication providing less than 50 nS sample-time difference between system modules separated by hundreds of meters. This precision hardware is supported by a complete range of testing software to accomplish virtually any type of test your enterprise requires.

A complete testing system consists of a VCS, a shaker, a power amplifier to drive the shaker and an accelerometer mounted on the shaker’s vibrating table. The VCS is programmed with the desired PROFILE of the test (either an acceleration-versus-frequency spectrum or an acceleration-versus-time history). It provides a low-voltage DRIVE signal to the power amplifier which echoes a high power version of this signal to the shaker. The response motion of the shaker’s table is monitored by the accelerometer which returns the CONTROL signal to the VCS. Sophisticated real-time algorithms and circuitry within the VCS function to refine the DRIVE signal with time, forcing the CONTROL response to match the desired PROFILE. The VCS also performs a myriad of related functions including pre-test feasibility analysis (can this shaker/amplifier perform this test on this DUT and its mounting fixtures?), test-result report generation, and network communication. 

Crystal Instruments’ sister company, Sentek Dynamics, provides permanent magnet and electrodynamic shakers, slip tables and power amplifiers. They offer air and water-cooled shakers with maximum force ratings from 20 N (4.5 lb) to 400 kN (88,000 lb) with strokes ranging from ± 4 mm (± 0.16 in) to ±100 mm (±3.9 in). Visit their website (www.sentekdynamics.com) for more detailed information.