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Among other components that work together as vibration testing system, accelerometer may be considered as one of the smallest one.
Yet, accelerometer is playing a very critical part to the accuracy of our vibration testing. Accelerometer is a sensor that measure acceleration.
Accelerometer has been majorly used for vibration testing, even though accelerometer is not the only type of sensor used.
Among other types of sensors (load cell, displacement sensor, etc), accelerometer may be considered as more practical and easier to deploy.
For vibration testing, accelerometer can be used as Control Sensor, to ensure that the vibration load (base motion) subjected to the UUT is still within our test specification.
Other than control sensor, accelerometer can also be used as measurement sensor, to check the response of the UUT during vibration testing.
Types of accelerometers:
Integrated Electronics Piezo-Electric (IEPE) Accelerometer.
According to its name, we will know that this type of sensor is based on piezoelectric material, a material that can produce electric current when it is subjected to acceleration at certain direction. This accelerometer also has built in amplifier that allows this sensor to be connected directly to vibration controller that can supply bias voltage.
Charge Accelerometer.
Unlike the previous type of accelerometer, this type doesn't have built in amplifier. Therefore, we need separate amplifier before connecting it to vibration controller. The advantage of this type of accelerometer is the ability to operate at higher temperature, compare to IEPE type. This type of accelerometer can be used for combined vibration and temperature testing by using combine vibration shaker and climatic test chamber. This type of accelerometer can be used for vibration measurement at high temperature area, such as engine, exhaust muffler, etc.
Micro Electro-Mechanical System (MEMS) Accelerometer.
Unlike IEPE accelerometer, MEMS type uses variable capacitance or piezoresistive concept to sense acceleration. The advantage of this of accelerometer is the ability to measure down to 0 Hz, makes them are sometimes called "DC Accelerometer". This type of accelerometer is useful for some automotive and aerospace application where they need static or DC acceleration measurement.
Based on the number of axis:
Uniaxial Accelerometer, which is an accelerometer that measures acceleration only at one direction.
Triaxial Accelerometer, which is an accelerometer that measures acceleration at three directions (X, Y, and Z).
Based on position of the cable insert:
Side Insert
Top Insert
Some of accelerometers mounting types:
Stud
Adhesive
Adhesive Mounting Base
Magnet Mounting Base
In general, using stud will be the most ideal way to mount our accelerometer, especially when we want to measure up to more than 5 kHz.
For vibration testing application, since most of the test frequency range will not go beyond 5 kHz, using adhesive will also be sufficient, especially when we have to change the sensor location for every different test or different UUT.
How to choose an accelerometer:
Define the frequency range requirement, based on our vibration measurement and/or vibration test requirement.
Define the sensitivity requirement, based on test acceleration level.
Select the mounting method according to test requirement.
If the test or measurement will be done in high temperature environment, ensure the accelerometer is able to withstand the environment.
Ensure the accelerometer has good enough frequency response within the entire test frequency range.
Check the size and weight of the accelerometer. Ensure that we have enough space to mount the accelerometer and ensure that the weight is low enough relatively to the total mass, in order not the create additional "mass loading", which can change the dynamic characteristic.
Determine if you need "Side Insert" or "Top Insert" type.
