Accelerometers

Accelerometers or vibration sensors are used to directly measure the acceleration or vibration of a test piece and indirectly measure velocity, displacement and tilt/inclination. There are two main categories of accelerometer the first utilise piezoelectric technology and are either amplified internally (IEPE/ICP®/CCLD accelerometers) or unamplified (charge mode accelerometers). The second incorporate MEMS sensing elements, allowing for static accelerations to be captured and include Capacitive and Piezoresistive accelerometers. StrainSense offer a wide range of accelerometers, including single-axis, biaxial and triaxial varieties for use in a number of applications, such as Crash, R&D, Rail, Military, Aerospace, Automotive Testing and Industrial Monitoring. Our accelerometers are fully customisable, with options for different body shapes and materials, cable and connector outlets, frequency response, acceleration and temperature ranges.

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Choosing the Right Type of Accelerometer

As you can imagine with a large proportion of engineering activities, choosing the incorrect tool may have serious implications on the results of your measurements. The information contained below is to help visitors make a more informative decision on an accelerometer sensor which is most appropriate for their requirements.

Accelerometer Types

In general, there are two widely known types of accelerometers:

  • AC-Response (called IEPE or ICP)
  • DC-Response (called MEMS or Piezo Resistive)

What is an AC-Response Accelerometer?

An AC-Responsive accelerometer means that the output is AC coupled. Essentially this means an AC coupled device cannot be used to fully measure static acceleration such as gravity and constant centrifugal acceleration meaning that it is only suitable for measuring dynamic events.

What is a DC-Response Accelerometer?

A DC-Responsive accelerometer means the output is DC coupled, meaning that this can respond down to zero Hertz (Hz). This ultimately means that it can be used to measure static, as well as dynamic acceleration. It is important to note however that measuring static acceleration is not the only reason a DC-response accelerometer should be selected.

If in doubt, speak to a member of our team today.


Acceleration, Displacement and Velocity

A large proportion of vibration studies that are made, require the knowledge of displacement, velocity and most importantly acceleration. These three elements helps engineers seek in designing of validating a structure / project. Most of the time, the g value provides good reference, however the other two (velocity and displacement) are two key variables that are also needed in most design calculations. To derive velocity and displacement from the output of acceleration, the signal from the accelerometer is not only integrated, by doubly integrated respectively in both analog and digital domains.

This is where an AC-response accelerometer may run into some trouble due to the output of this device never being able to track the peak of the half-since input due to the intrinsic limitation imposed by its RC time constant. Here's a quick picture to illustrate the problem;

Accelerometers-Technical-Output

At the end of the half-sine pule, it's important to note that the output of the AC coupled accelerometer will produce an undershoot (more commonly known as an offset) for the very same reason. The red tracing line in the graph above depicts the output of an AC coupled device following a long duration half-sine input.

This example is a commonly occurring trouble shooting problem that we hear from clients across a wide range of industries.

Frequently Asked Questions About Accelerometers

Accelerometers are sensors designed to measure proper acceleration in various industries and devices. They're utilized in applications such as automotive systems (airbag deployment, vehicle stability control), aerospace (flight control systems), medical devices, robotics, industrial machinery (vibration monitoring), and structural health monitoring.

Accelerometers function based on the principle of inertia. They contain a mass that moves in response to acceleration, generating an electrical signal or change that's measured to determine the acceleration's magnitude and direction.

Common types include MEMs (Micro-Electro-Mechanical Systems) accelerometers, piezoelectric accelerometers, piezoresistive accelerometers, and capacitive accelerometers. MEMs accelerometers are particularly prevalent due to their compact size and cost-effectiveness.

The accuracy of an accelerometer varies based on quality, calibration, and environmental factors. High-quality accelerometers can offer precise measurements within their specified range.

Accelerometers primarily measure linear acceleration along specific axes. While they indirectly indicate changes in orientation or tile using gravity's effect, for precise angular measurements, complementary sensors like gyroscopes are used in inertial measurement units (IMUs).

Accelerometers might face challenges in accurately measuring high-frequency vibrations, rapid changes in acceleration, or when multiple axes of acceleration need simultaneous and precise monitoring in specific industrial or scientific applications.

Calibration involves exposing the accelerometer to known accelerations to ensure accurate measurements. This process might involve software adjustments or physical testing in controlled environments to align the device's readings with the actual accelerations.

Consider the required measurement range, sensitivity, power consumption, size, environmental conditions (such as temperature and humidity), and the specific demands of the application to choose the most suitable accelerometer.

Yes, accelerometers are commonly used for structural health monitoring in various industries, allowing continuous monitoring of vibrations, changes in acceleration, and potential structural weaknesses in machinery, bridges, buildings, and other structures.

In robotics and automation, accelerometers aid in monitoring motion, ensuring precise movements, detecting impacts or changes in orientation, and enhancing overall system control and safety measures.

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