Frequently Asked Question

Frequency Response
Last Updated 2 years ago

Frequency Response is the bandwidth of signals which our sensors can measure. Normally the MEMS itself has already a frequency response (e.g. 0-18Hz), for a better output, we have also designed extra low pass filters.

The movements/vibrations are unwanted signals when you are measuring the angle. That’s why we set the -3dB cut-off frequency to 10Hz, which means 0-10Hz signals will pass through and >10Hz will be significantly attenuated. In this way, we can have stable angle information with much less noise.


The picture below will give you an idea. As a result, the output you see will have a little delay due to the filter time (RC time τ)

image
Frequency Response of a 1st-order Low Pass Filter



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(e.g. 30KHz goes through, and 300Khz signals are attenuated to almost half of its amplitude and has a phase shift)

The RC time (Time constant τ) is calculated with the 3dB cut-off frequency. It is the time in which the output changes to about 63.2% of the step after a step response. 

image


The actual response time(delay time) should be 5τ. 

image
Exponential Voltage Growth Over Time

For example, If you set the cut-off frequency to 3Hz, the RC time τ=50ms, the total response time of the sensor will be about 50*5=250ms.





For more knowledge over frequency response and low pass filter, please find it here:

https://en.wikipedia.org/wiki/Frequency_response

https://www.electronics-tutorials.ws/filter/filter_2.html

https://www.electronics-tutorials.ws/rc/time-constant.html

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