# Frequently Asked Question

**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 of the 1st order low pass filter. As a result, the output you see will have a little delay due to the filter time (RC time **τ)**

(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.

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

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.

There are different low pass filters, here below give you a comparison of the frequency response of the 1st order low pass filter and the 2nd order low pass filter.

The drop slope of the 1st order LPF is -20dB/Decade, which means when frequency increase 10 times, the slope drops -20dB. If the -3dB frequency is 10Hz, -23dB frequency is therefore 10*10Hz. -43dB frequency is therefore 10*10*10=1000Hz.

The drop slope of the 2nd order LPF is -40dB/Decade, which means when frequency increase 10 times, the slope drops -40dB. If the -3dB frequency is 10Hz, -43dB frequency is therefore 10*10^1Hz. -83dB frequency is therefore 10*10^2=1000Hz.

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