Page 11 - Shock and Vibration Overview

Sensor Selection

and vibration measurement systems by incorporating a high quality piezoelectric
accelerometer as opposed to the cheaper capacitive MEMS accelerometers found in
most vibration data loggers.

Figure 3: The Slam Stick X is shown that incorporates the accelerometer, power, and data
acquisition electronics into one small handheld package.

Shock and vibration data loggers generally have much shorter lead time (a few days) and
lower cost ($500 to $2,000) than building your own vibration measurement system.
There are a lot of different companies that make shock and vibration data loggers and a

lot of different options; here’s a post comparing 6 different products.

Non-Contact Displacement Sensors

Although accelerometers are the most popular choice in shock and vibration
measurement, displacement sensors measure the displacement of a vibrating structure.
Calculating between displacement, velocity, and acceleration is accomplished with
integration/differentiation (here’s a calculator for simple harmonic motion applications).
The downside to using these is that it’s measuring relative motion between two

structures. These are near impossible to use in the field because a fixed mounting and
distance is required between the sensor and equilibrium position of the vibrating
structure. They can also be quite a bit more expensive and complex than accelerometer
based systems. That being said, displacement sensors can be preferred in some
applications that prevent the use of accelerometers such as rotating components
(although a data logger could be used), or when the accelerometer’s mass would too
greatly influence the motion of the system. Generally displacement sensors should be
avoided for shock testing for fear of damaging the sensors.

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