A Technical Guide to Selecting the Right Shaker System for Your Application
Introduction
Selecting the appropriate vibration shaker system is a critical decision that impacts testing accuracy, product reliability, and operational efficiency. This comprehensive guide walks you through the essential considerations when acquiring a shaker system, from understanding fundamental specifications to evaluating control system requirements.
Whether you're conducting production screening, R&D prototype testing, or compliance verification for aerospace, automotive, defense, or electronics applications, understanding these key parameters will help you make an informed purchasing decision that aligns with your testing requirements and budget constraints.
1. Understanding Shaker Types
The first critical decision in your acquisition process is selecting the appropriate shaker technology for your testing requirements. Each type offers distinct advantages and is optimized for specific applications.
Electrodynamic (ED) Shakers
Electrodynamic shakers are the most common type used for vibration testing. They operate on electromagnetic principles, using a voice coil within a magnetic field to generate controlled vibration.
Best Applications:
• Sine vibration testing (swept sine, resonance search)
• Random vibration testing (broadband and narrowband)
• Shock and shock synthesis waveforms
• Complex multi-axis testing with slip tables
Key Advantages:
• Wide frequency range (typically 2 Hz to 2000 Hz or higher)
• Precise control with closed-loop servo systems
• Clean, reproducible test waveforms
• Compatible with advanced digital control systems like PANTHER
Hydraulic Shakers
Hydraulic shakers use hydraulic actuators to generate vibration forces. They excel in applications requiring very large displacements or extremely high force levels at low frequencies.
Best Applications:
• Large displacement testing (building, bridge, automotive suspension)
• Low-frequency, high-force applications (0.1 Hz to 100 Hz typical)
• Seismic simulation and earthquake testing
• Full-scale structural testing
Modal Shakers
Modal shakers are specialized systems designed for modal analysis and structural dynamics testing. They're typically smaller, portable units optimized for impact testing and frequency response function (FRF) measurements.
Best Applications:
• Experimental modal analysis (EMA)
• Operating deflection shape (ODS) measurements
• Structural health monitoring
• Product development and validation
Shock and Drop Test Systems
Shock test systems generate high-amplitude, short-duration pulses to simulate impacts, drops, and crash scenarios. These can be pneumatic drop tables, mechanical shock machines, or specialized shock synthesis capabilities within electrodynamic systems.
Best Applications:
• Package and shipping container testing
• Munitions and ordnance qualification
• Automotive crash pulse simulation
• MIL-STD-810 shock testing
2. Critical Performance Specifications
Understanding and properly specifying performance parameters ensures your shaker system meets both current and future testing requirements. These specifications directly impact what tests you can perform and the quality of your test results.
Force Rating
The force rating is the most fundamental specification, typically expressed in pounds-force (lbf) or Newtons (N). Account for fixture weight, test specimen weight, and safety margin (typically 1.5x to 2x total mass).
Sizing Formula:
Required Force = (Specimen Weight + Fixture Weight) × Max Acceleration × Safety Factor
Acceleration, Velocity, and Displacement
These three interrelated parameters define the shaker's performance envelope. Modern control systems like PANTHER continuously monitor all three limits and automatically prevent over-testing by monitoring over a dozen critical safety parameters up to 25 times per second.
Frequency Range
The usable frequency range must cover your required test standards with adequate margin. Typical electrodynamic shakers operate from 2 Hz to 2000 Hz or higher, while hydraulic systems excel at lower frequencies (0.1-100 Hz).
3. Size and Physical Configuration
Table Size
Select table size based on current and anticipated test specimen dimensions. Remember that larger tables add moving mass, reducing effective acceleration capability.
Cooling: Air vs. Water
Air-cooled systems offer simpler installation and lower maintenance, while water-cooled systems provide superior cooling for continuous operation and high-duty-cycle applications.
Installation Orientation
Vertical configurations are most common and require less floor space. Horizontal installations ease specimen loading but require more laboratory area.
4. Slip Tables and Multi-Axis Testing
Slip tables enable horizontal axis testing with vertical shakers, providing flexibility for testing specimens in multiple orientations. They use precision air or oil bearings to provide low-friction motion transfer.
When You Need a Slip Table
• Three-axis qualification testing requirements
• Horizontal testing without reconfiguring shaker
• Simplified specimen mounting for certain orientations
• Comprehensive product qualification programs
Hydrostatic (oil) bearings offer higher load capacity, while aerostatic (air) bearings provide cleaner operation and extremely low friction. Choose based on load requirements and maintenance preferences.
5. Fixtures and Mounting Considerations
Proper fixturing is essential for accurate testing. Ideal fixtures have high stiffness, low mass, and first resonance well above maximum test frequency.
Fixture Design Principles
• First resonance should be at least 2x higher than maximum test frequency
• Minimize mass using lightweight materials (aluminum, magnesium, carbon fiber)
• Maintain symmetric mass distribution
• Include provisions for control accelerometer mounting
6. Vibration Control System Requirements
The control system is the intelligence behind your vibration testing. Modern digital systems like PANTHER provide sophisticated closed-loop control, comprehensive safety monitoring, and advanced test capabilities.
Why Servo Control is Essential
Closed-loop servo control automatically compensates for shaker dynamics, maintains precise amplitude control, and provides real-time safety monitoring. Systems like PANTHER monitor over a dozen critical parameters up to 25 times per second.
Essential Control System Features
• Multiple control modes: Sine, Random, Shock, Mixed-Mode
• Multi-channel capability (8+ channels minimum, expandable to 32)
• High dynamic range (>110 dB input, >100 dB output)
• 24-bit ADC with 20-bit DAC for optimal closed-loop control
• System identification and automatic equalization
• Comprehensive alarm and abort limits
Advanced Control Algorithms
PANTHER employs patented adaptive digital vibration control methods optimized for each test type, including true Gaussian random generation, optimal adaptive tracking filters for sine control, and specific linear phase filters for shock waveforms.
7. Supporting Equipment
Power Amplifiers
Power amplifiers must match shaker electrical requirements for continuous and peak power, frequency response, and cooling method.
Cooling Blowers
Supplemental cooling extends duty cycle for air-cooled shakers, especially important for continuous random testing or high-level applications.
Accelerometers and Sensors
High-quality accelerometers for control, response monitoring, and limit channels are essential for accurate closed-loop operation.
8. Facility Requirements
Foundation and Seismic Mass
Seismic mass should be 10-20x the combined weight of shaker, amplifier, and maximum test load. Proper isolation prevents vibration transmission to building structure.
Electrical Power
Dedicated circuits with adequate capacity (often 60-200+ amps). Larger systems typically require 208V or 480V three-phase power.
Cooling Water and Compressed Air
Water-cooled systems require 2-10 GPM clean water at 40-60 PSI. Air-bearing slip tables need clean, dry, oil-free compressed air at 80-100 PSI.
Environmental Conditions
Maintain laboratory temperature 15-30°C (60-85°F) and humidity 20-80% RH with adequate ventilation for heat dissipation.
9. Performance Verification
Factory and Site Acceptance Testing
Comprehensive testing verifies performance before shipment and after installation. This includes mechanical inspection, bare table acceleration verification, displacement/velocity limits, and reference test execution.
Performance Documentation
Document frequency response, cross-axis motion, control system calibration, and accelerometer certificates to establish baseline performance for future verification.
10. Budget and Total Cost of Ownership
Initial Capital Investment
Include shaker, amplifier, control system, slip table, accelerometers, fixtures, seismic mass, installation, training, and spare parts in your capital budget.
Facility Preparation Costs
Account for foundation construction, electrical upgrades, cooling water, compressed air, HVAC modifications, and safety barriers.
Operating Costs
Annual expenses include electrical power, cooling utilities, maintenance, calibration, replacement parts, and software support.
11. Vendor Selection Criteria
Company Experience
Select vendors with decades of vibration testing experience, extensive installed base, and proven track record. Spectral Dynamics has over 60 years of experience in closed-loop digital vibration control.
Technical Support
Evaluate pre-sale consultation, installation support, training programs, ongoing technical support, and test method development assistance.
Control System Technology
Honest engineering specifications matter more than marketing claims. PANTHER provides realistic 110 dB input and 100 dB output dynamic range versus competitors' theoretical claims that cannot be achieved in real-world testing.
Spare Parts Availability
Verify stock of critical components, shipping times, parts availability for older systems, and field service technician availability.
12. Requirements Checklist
Use this comprehensive checklist to ensure all critical factors have been considered in your shaker acquisition decision.
Requirement
☐ Shaker type selected (ED, Hydraulic, Modal, Shock)
☐ Force rating specified (sine and random)
☐ Maximum acceleration requirement defined
☐ Displacement limits calculated
☐ Frequency range requirements established
☐ Table size and configuration determined
☐ Cooling method selected (air vs. water)
☐ Slip table requirement evaluated
☐ Fixture strategy developed
☐ Control system capabilities specified
☐ Channel count requirements defined
☐ Foundation design completed
☐ Electrical power requirements verified
☐ Cooling water / compressed air planned
☐ Environmental chamber integration evaluated
☐ Accelerometer and sensor requirements specified
☐ Budget approved (including facility costs)
☐ Vendor evaluation completed
☐ Service and support agreement reviewed
☐ Acceptance test protocol defined
☐Training plan established
☐ Installation timeline coordinated
Conclusion
Acquiring a vibration shaker system represents a significant investment in your organization's testing capabilities. By carefully considering each factor outlined in this guide—from fundamental shaker type selection through control system requirements, facility preparation, and long-term support—you can make an informed decision that serves your testing needs for decades.
The most successful installations result from early planning, realistic budgeting, and close collaboration between testing engineers, facility managers, and equipment vendors. Companies like Spectral Dynamics, with over 60 years of vibration testing experience, provide the technical expertise and comprehensive support that transforms equipment purchases into long-term partnerships.
Remember that honest engineering specifications matter more than marketing claims. Systems like PANTHER, which provide realistic dynamic range figures and proven adaptive control algorithms, deliver superior real-world performance compared to competitors making theoretical claims that cannot be achieved in actual vibration testing environments.
About Spectral Dynamics
Spectral Dynamics is a leading manufacturer of vibration testing equipment and control systems with over 60 years of experience in closed-loop digital vibration control. Our PANTHER vibration control system represents the culmination of decades of engineering innovation, combining extraordinary accuracy, optimum dynamics control, unparalleled adjustability, and expandability in both hardware and software.
PANTHER is designed for both production screening and R&D prototype testing, offering a user-friendly graphical interface alongside the sophisticated control algorithms required for the most stringent test requirements. With superior control capabilities including patented adaptive digital vibration control methods, comprehensive safety monitoring, and industry-leading technical support, Spectral Dynamics helps testing engineers worldwide achieve accurate, repeatable results.
For more information about Spectral Dynamics products and services, please visit www.spectraldynamics.com or contact our applications engineering team at 1-800-778-8755.
