Shaker Comparison Table
| FACTOR | ELECTRODYNAMIC | REPETITIVE SHOCK (RS) |
|---|---|---|
| Number of Axes per Shaker | One | Six |
| Simultaneous Multiple Axis Capability | One or more shakers per axis (complex control algorithms) or diagonal (skewed) force vector input | Yes |
| Typical Range of Product Mass | Thousands of pounds | Possible: Low hundreds of pounds Practical: Less than 100 lbs |
| Energy Source | Electrical | Pneumatic |
| Typical Frequency Range | Less than 5 to 2,000 Hz | 10 to more than 5,000 Hz |
| Controllable Spectrum | Yes | No |
| Force Limiting Factors | Armature mass, field supply, aplifier cooling capacity. | Piston mass, impact velocity, piston/fixture coupling, distance from impact point, modal characteristics of plate |
| Low Frequency Energy | Yes, controllable | Minimal |
| Can be used for Simulation Testing | Yes | No |
| Can be used for Stimulation Testing | Yes | Yes |
| Input Displacement Range | Inches applied to entire fixture and product | Microinches, applied locally to fixture impact points |
| Spectral Characteristics | Continuous control in each filer band; sine, random, shock, sine-on-random, narrowband-on-broadband vibration | Uncontrolled (open loop) spectrum with periodic "holes" and spikes, "quasi-random" vibration only |
| Spectrum Limiting Factors | Fixture resonances, number of filters, ED armature/test mass resonance (~2500 Hz) | Open-loop control, piston repetition rate, fixture resonances and nodes, GRMs control only |
| Product Characterization | Straight forward analysis | Analysis complicated by untailorable spectrum |
| Uniformity on Table | Very uniform | Not uniform |
| Mechanical Shock Pulses | Classical waveform, shock spectrum, pyrotechnic | No control capability |
| Acoustic Noise | Varies with spectrum, fixture, and product design, and input force level | Very loud (could affect performance of noise-sensitive products) |
| Electromagnetic Fields | Magnetic fields can affect some products; may require degauss coil | No effects |
* Table from "Fundamentals of Accelerated Stress Testing Handbook" offered as download by Thermotron.