ED or EH vibration shakers?

Introduction to Vibration Test Systems: Electrodynamic and Electrohydraulic Shakers

Vibration test systems are used extensively in product qualification, research and development, and durability testing. This article introduces and compares two primary technologies:

Electrodynamic (ED) shakers and Electrohydraulic (EH) shakers.

What Is a Vibration Test System?

A vibration test system is designed to apply controlled mechanical vibration to a component or structure, simulating the dynamic loads encountered during transport, operation, or real-world service environments. The goal is to uncover mechanical weaknesses, fatigue points, or resonance-related issues before field deployment.

At its core, the system generates a forced vibration with defined frequency and amplitude. In its simplest form, like a motor with an eccentric cam, the unbalanced mass creates periodic forces. However, modern systems offer far more precision, range, and control.

Electrodynamic Shakers (ED)

Electrodynamic shakers operate on the same Lorentz force principle as loudspeakers. A moving coil (voice coil) is suspended within a static magnetic field generated by permanent magnets or field coils. When an alternating current passes through the coil, a force is generated proportional to the current and the magnetic field. This moves the coil, and the attached armature, back and

forth.

The Audio Speaker and the Electrodynamic Shaker

Key characteristics:

• Frequency range: Typically 5 Hz to 2,500 Hz or higher

• Control: Excellent for sine, random, shock, and classical waveform testing

• Cooling: Air or water-cooled options depending on force rating

• Applications: Electronics, aerospace components, automotive assemblies, small mechanical parts

The armature (analogous to the speaker cone) serves as the mounting platform for the test item. ED shakers are often used with slip tables (for horizontal excitation), head expanders, and guided fixtures to support a wide variety of test configurations.

Electrohydraulic Shakers (EH)

Electrohydraulic shakers, also known as servo-hydraulic actuators, use pressurised oil to actuate a piston in a two-chamber cylinder. The direction and magnitude of the force are controlled by a servo valve, which rapidly switches the oil flow between chambers.

While derived from the hydraulic systems used in industrial machinery (e.g., excavators), EH shakers are specifically engineered for high-speed dynamic performance.

Key characteristics:

• Frequency range: Typically 0.1 Hz to 500 Hz (can vary based on system design)

• Stroke capability: Much longer displacement than ED shakers, often over 100 mm peak-to-peak

• Force: Suited for high-force applications (100 kN and above)

• Applications: Structural testing, civil engineering, vehicle chassis, large assemblies

Due to their high stroke and force capabilities, EH systems are ideal for low-frequency, high-displacement testing such as road simulation, seismic simulation, and structural fatigue assessments.

Which Shaker Should You Choose?

The selection depends on your application needs:

Criteria	Electrodynamic (ED)	Electrohydraulic (EH)
Frequency range	Mid to high (1 Hz–2.5 kHz+)	Low (0.1–500 Hz)
Displacement	Typically ≤ 100 mm p-p	Typically ≥ 100 mm p-p
Force	Up to ~100 kN (typical)	Up to several hundred kN
Signal fidelity	Excellent	Good for lower frequencies
Typical applications	Electronics, aerospace	Automotive, structures
Maintenance	Lower	Higher (hydraulics intensive)

In many cases, modern testing programs may require both types. For example, ED shakers can address high-frequency fatigue or resonance issues, while EH systems handle long-duration, low-frequency stress tests.

Find out more about:

Data Physics electrodynamic vibration test systems:  https://www.resonatesystems.com.au/data-physics-signalforce

EMIC electrodynamic vibration test systems: https://www.resonatesystems.com.au/vibration-test-systems

TEAM electrohydraulic vibration test systems: https://www.resonatesystems.com.au/team-electrohydraulic-test-systems