High Frequency  Electrodynamic shakers Purchasing Guide

Selecting the right high frequency vibration test machine is crucial to meet the specific needs and requirements of your industry. This purchasing guide will provide you with detailed information and specific data to help you make an informed decision. It takes into consideration industry pain points, hotspots, and international standards. Please find below the detailed guide in English.

Required Testing Conditions

To select an appropriate electric platform, it is important to provide the following information regarding your vibration testing conditions:
1. Frequency range (in Hertz, Hz) for the vibration test.
2. Magnitude of shaker test parameters such as acceleration (m/s² or g), displacement (mmp-p or p), velocity (m/s), or acceleration spectral density (PSD) values (g²/Hz or m²/s³).
3. Vibration test direction: Whether it is a single-axis vertical test or three-axis (XYZ) test.
4. Dimensions (length, width, height) and weight of the test specimen.
5. Weight of the test specimen (in kilograms, kg).

Electric Platform Selection Calculation
Based on the maximum dimensions and weight of the test specimen, choose a vertical expansion platform.
The electric platform acts as the vibration source, and its working platform size is small, mainly used for fixture installation and expansion. Therefore, determine the size and weight of the expansion platform or fixture before the selection calculation. The main technical parameters of the vertical expansion platform are its dimensions, weight, and upper frequency limit. The maximum dimensions of the test specimen should be smaller than or equal to the expansion platform size, and the upper frequency limit of the vibration test should be smaller than or equal to the vertical expansion platform's upper frequency limit. Therefore, the dimensions and weight of the expansion platform can be determined based on the maximum dimensions and highest test frequency of the test specimen. The following data is for reference purposes only, as the specifications of the vertical platform or horizontal slide platform in different vibration equipment configurations may vary due to the different materials used.

Choose a horizontal slide platform based on the vibration test direction

If the vibration test of the test specimen is only required in the vertical direction, then the vertical expansion platform is sufficient. However, for general vibration tests that require three-axis (axial) vibration of the test specimen, the fixed position during the vibration test should simulate the fixed position of the test specimen in its working or transport state as much as possible.
If there are no specific installation position requirements for the test specimen in its working or transport state, i.e., if changing the center of gravity of the test specimen by flipping it does not affect its performance, then three-axis vibration of the test specimen can be achieved by fixing the vibration direction of the electric platform and changing the center of gravity of the test specimen. In this case, only a vertical expansion platform is required. However, for large test specimens, a horizontal slide platform is sufficient due to the large size of the electric platform required.
If there are specific installation position requirements for the test specimen in its working or transport state, i.e., if changing the center of gravity of the test specimen by flipping it affects its performance, then the vibration direction of the electric platform needs to be changed to achieve three-axis vibration of the test specimen while keeping the center of gravity of the test specimen unchanged. In this case, both a vertical expansion platform and a horizontal vibration slip table are required.
The technical specifications of the SC series horizontal slip table produced by ALITETSING——JOEO are provided below for reference. The selection process for the horizontal slide platform is similar to that of the vertical expansion platform. Note: The higher the upper frequency limit, the higher the required rigidity coefficient and the heavier the platform components. The calculation for the maximum acceleration in vibration testing is as follows:

Sinusoidal Vibration Test Conditions are generally divided into:
1) Constant Acceleration Swept Sine Test: f1--f2, Acceleration A1. In this test, the maximum acceleration within the frequency range from f1 to f2 is A1. The conversion formula for displacement D during swept frequency vibration is: D = A1×103/(2πf)2. Thus, the maximum displacement is D1MAX = A1×103/(2πf1)2.
2) Constant Velocity Swept Sine Test: f1--f2, Velocity V. The conversion formula between velocity and acceleration is: A = (2πf)V, where A is in m/s² and V is in m/s. Thus, the maximum acceleration is A2MAX = (2πf2)V. The conversion formula for displacement D during swept frequency vibration is: D = V×103/(2πf). Thus, the maximum displacement is D2MAX = V×103/(2πf1).
3) Constant Displacement Swept Sine Test: f1--f2, Displacement D. The conversion formula between displacement D and acceleration A is: A = (2πf)2D×10-3, where A is in m/s² and D is in mm. Thus, the maximum acceleration is A3MAX = (2πf)2D×10-3, and the maximum displacement is D.
4) Multiple Segment Swept Sine Test with Constant Acceleration and Constant Displacement. The maximum acceleration for each segment is calculated as mentioned above, and then the maximum value is selected from A1, A2MAX, and A3MAX as the maximum acceleration for the test conditions. Similarly, the maximum displacement is calculated from D1MAX, D2MAX, and D, and the maximum value is selected as the maximum displacement for the test conditions.

The calculation for the maximum acceleration of random vibration is as follows:
For random vibration test conditions with given frequency range, spectral density value, and root mean square acceleration value (ARMS), the ARMS value is the maximum acceleration required. If the ARMS value is not provided, it needs to be calculated separately. The test conditions can be input into the random vibration test control instrument (software) to calculate the ARMS root mean square acceleration value and the Drms vibration amplitude.

1. Calculate the acceleration value a based on the user's specified requirements. The test conditions are as follows:
20-80Hz, 3 dB/oct; 80-350Hz, 0.04g²/Hz; 350-2000Hz, -3 dB/oct.

2. The calculation is as follows:
1) For ascending spectrum (slope N1 dB/oct):
Where m = N1/3.
 Then, F1 = 0.04×80[1-(20/80)²]/(1+1) = 1.5.
2) For flat spectrum:
   F2 = P(f3 - f2) = 0.04×(350-80) = 10.8.
3) For descending spectrum (slope -N2 dB/oct):
From F3 = 0.04×350[-ln(350/2000)] = 24.5.
The formula for a is a = √(F1 + F2 + F3).
Therefore, a = √(1.5 + 10.8 + 24.5) = 6.06g.

3. According to Newton's second law (F = ma), calculate the force F:
 F = (M1 + M2 + M3)×a,
 where:
 M1 - Weight of the electric platform moving parts (kg).
 M2 - Weight of the vertical expansion platform, horizontal slide platform, or fixture (kg).
 M3 - Maximum weight of the test specimen (kg).
 a - Maximum acceleration of the vibration test (m/s²).

The force F should be less than or equal to the maximum sinusoidal excitation force of the electric platform.
For random vibration, the force Frms is calculated as Frms = M×Arms and should be less than the rated random excitation force of the electric platform.

4. Confirm that the maximum displacement of the electric platform is greater than the maximum displacement in the test conditions. For random vibration, the root mean square amplitude Drms calculated by the computer should be less than one-third of the rated amplitude of the electric platform.

5. Select a sine control instrument or random vibration control instrument based on the specified test conditions. If there are parameters for random vibration, a random vibration control instrument must be chosen.

Conclusion

When selecting a high frequency vibration tester, it is crucial to consider the specific requirements of your industry, including testing conditions, electric platform selection calculation, force calculation, and the need for sine or random vibration control. By following this purchasing guide and considering the detailed specifications and requirements, you can choose the most suitable high frequency vibration tester for your industry.

Please note that this guide provides detailed information based on industry needs, pain points, and international standards. It is recommended to study the product manuals and relevant specifications to ensure the purchased equipment meets your specific requirements before actual use.