Reducing noise in accelerometers

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Jennifer MacDonell, product director, MEMS at Endevco, stresses the importance of damping accelerometers.

What is the background to your presentation?

Endevco has been at the forefront of accelerometers for automotive safety testing for decades. During that time, we have learned about what is important in automotive applications and modified the solutions we offer accordingly. First, we identified that the ringing of undamped accelerometers was interfering with measurements and hurting accuracy. In response, we introduced multi-mode damping, which prevents significant resonant amplification up to 40kHz.

Next, we noticed that the industry had standardized on 2,000g accelerometers despite most of the measurements being closer to 200g. It should be obvious that when the measurement range is only a tenth of the sensor’s full scale, the test result may be seriously compromised.

My presentation will introduce new double-sensitivity 2,000g accelerometers that will dramatically improve signal-to-noise ratio in automotive safety applications.

How are you improving accelerometer measurements?

Most of what we know about damping has been known in the macro sense for a long time. However, that doesn’t mean that knowledge is always in the hands of everyone who needs it. At Endevco, we believe gas damping is preferable to fluid damping because the fluid damping ratio can vary pretty widely with temperature as the fluid becomes more or less viscous.

Our multi-mode gas damping is more effective than traditional gas damping because we are damping both the first and second resonance modes of the accelerometer. The big benefit of this is that there is no significant resonance at or near the frequency range of interest. Many say that filters can be applied to correct the ringing in the data, but if ringing of the accelerometer has caused it to behave in a non-linear way, that correction may not be enough. Once you integrate to get velocity, that error will snowball further.

What are the challenges with this approach and how will the technology develop in the future?

The first major step is educating customers. We have already made a significant effort to stress the importance of damping and the risks associated with not having it, particularly where metal-to-metal impact is involved. Currently, we are emphasizing the advantages of having high-output piezoresistive accelerometers for better signal-to-noise performance. The next step is to expand our gas-damped product line into lower ranges so that customers can choose the range best suited to their application.

Catch Jennifer’s presentation “elevate your measurement with double sensitivity” at the free-to-attend Technology Demonstration Area. View the full program here.

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Illya joined UKi Media & Events in 2018 having completed an Automotive Journalism MA course at Coventry University. As expo news editor, he writes about the new products and technologies that can be found at UKi Media & Events' many exhibitions, as well as contributing to UKi's various magazines and websites.

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