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AD resolution of the MTi 10-series and MTi 100-series

The MTi 10-series and MTi 100-series use analog inertial sensors, that are processed by an AD converter. A question that is often raised is the resolution of this AD converter. There is more to it than just the resolution of the AD converter: this article provides more background information.  

AD converter

The AD converter that Xsens uses for the MTi 10-series and MTi 100-series is a 10 kS/s simultaneous AD converter. The fact that the AD converter is simultaneous is extremely important. It is a more expensive technology but allows that the 3 axes of the gyroscopes and accelerometers are samples and processed at the same instant, so that the calibration that Xsens applies to the individual axes are valid. If a cheaper AD converter is used, the sampling is sequential, which could mean that the inertial sensors have already rotated a little bit. This means that the gyroscope vector (XYZ) may contain more movement from the x-gyroscope than y-gyroscope or more from the z-gyroscope than from the x-gyroscope. 

The system architecture of the MTi showing the 6-channel AD converter in the top left

The AD converter itself has a 16-bit resolution. However, as the inertial sensors are sampled at 10 kHz, the actual resolution when outputted at 400 Hz to the user is much higher. The actual, effective resolution of the 400 Hz output cannot be stated as this depends on e.g. noise values. 

Output format

The output format of the MTi can be chosen as Floating point 32-bit, Fixed Point (12.20 or 16.32) or Floating Point 64-bit. This article (link) describes the various output formats for position output. For inertial data, Floating point 32-bit is sufficiently accurate to capture all the noise and signals. 

 

 

 

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