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Fundamental and Selection Method

It’s intricate but very important to select the model of vibration testing system, it must refer to test specifications, test standards, specimens, fixture, vibration test system, controller and measurement sensors, etc. Customers must think it over and communicate with the suppliers more than one time. Here we provide you some important parameters you must consider when you select the right model of vibration testing system.

Required Exciting Force

The working principle of electrical-dynamics vibration system is using the fixed magnetic field and armature which is with current and inside of the fixed magnetic field interacting to generate exciting force. When armature coil with alternating current, armature generates corresponding alternating motion.
Exciting force which test required is equal to the product of mass of moving parts and test acceleration.

F=m×A

When the mass of armature is m0, the weight of head expander (or slip table) and fixture is mf, weight of specimen is ms, the required exciting force is F=( m0+ mf+ ms)×A You can get the weights of moving parts and head expander/ slip table from the manufacturers.
According to the calculating exciting force, customers can select the suitable vibration testing system.
For example, customer has a specimen which is 30 kg weight, the mass of head expander and fixture is 20 kg, max. acceleration is 15g, weight of moving parts is 10 kg (pre-selection of vibration system is DC-1000-15 and the weight of armature is 10 kg), so the force of the system is 
F=( m0+ mf+ ms)×A= (30+20+10)×15=900 kg. Select DC-1000-15 can meet customer’s requirements. Rated force of DC-1000-15 is 1000 kg.

Because of the characteristics of fixture and specimen, customers need to maintain at least 10% allowance of exciting force when select the vibration system. 

Relationships of Max. Acceleration, Max. Velocity, Max. Displacement and Frequency
When sine vibration, the relationship of frequency (Hz), Displacement (Dmm0-p) and velocity (V m/s) is shown as following. 

V=(2πf/1000)×D
A=(2πf) ×V=(2πf)2/1000×D

Consider Acceleration, Velocity, Displacement and Frequency Range, etc
Max. Acceleration without payload     the max. acceleration which vibration system generates when it without payload, generally, this value is equal to vibration exciting force divided by the weight of moving parts.

Max. Velocity         the max. velocity that vibration testing system can reach to, it’s limited by length of armature’s winding coil and max. output voltage of power amplifier. 

Max. Displacement    the max. displacement which is generated by vibration testing system, it’s limited by the displacement protection device, using single amplitude (0-p) or peak-to-peak amplitude to indicate.

Frequency Range      according to some variables, vibration test system can be applied to the range of frequency, for example, max. displacement, max. velocity, max. acceleration.

Rated Exciting Force    the rated exciting force which is generated by vibration test system. When sine vibration, this value means the peak force, when random vibration, it means RMS value. It’s limited by the allowed max. current which is through the armature coils.
Max. Test Payload      the max. payload that vibration test system can bear. It’s limited by the armature support air spring of vibration test system, but customer can choose auxiliary support device to expand the carrying capacity of vibration test system.


Controller Selection

To choose controllers is mainly considered the test type and function, according to test specification or test standard of products, select the suitable test type. Commonly, there are the sine, random, classical shock, waveform reappear and so on. What’s more, you also need to consider how many control points and test points, and input/output channels, the type of sensors you will use which is IEPE or charge input type, etc.  


Options Selection

There are lots of available options in our company, in order to complete customer’s vibration tests preferably and conveniently. The basic options are HCC-1, head expander, slip table, auxiliary support device, auxiliary guidance device, electric moving device