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Relative movement of two MetaMotion modules

ssuatsssuats
in General
I have some technical questions related to the "Meta Motion R – 10 Axis IMU + Sensor Fusion":

1) I would like to record the differential 3D position of two MetaMotion, i.e. how the two positions of the MetaMotion move relatively to each other. The relative movement would have a range of about 0-30mm in one case and 0-200mm in another case with a frequency of movement of about 5-10Hz. 
Would the sensor signals be accurate enough to get reasonable data for such application?

2) in order to achieve no. 1) I would need to synchronize the logged samples from two MetaMotion very accurately. I read about synchronization of sensors of a single MetaMotion here, but I need to synchronize sensor data from tow different MetaMotion. So my questions are: 
What are the mechanisms to synchronize the time stamps of the two MetaMotion? 
What would be the resolution of the timestamp and maximum error of the synchronization? 
What would be the jitter of the sample rate and the latency of the sampled data? 

3) I need high data rate, up to 800 samples per second in order not to miss changes in the relative position. Therefore I would like to ingelligently filter data directly on the MetaMotion in order to limit logging to about 50 entries per second. 
Is there a way to achieve that with the current iOS / C++ APIs? 
If not for logging mode, would filters effectively reduce traffic on the bluetooth cannel in streaming mode or do they just filter received data?

4) I would like to log sensor fusion samples as well as all the 9 axis separately. 
Would it be possible to log one record of all sensor data "atomically", i.e. are all the values of one sample period saved as one record in into the flash so that these values are synchronized?
What is the maximum sample rate of sensor fusion data to the flash log?
What is the maximum amount of entries that can be logged to the the flash of the device? 

5) What would be the battery life of one 100mAh charge in sensor fusion mode with 100, 200, 400, 800 Hz of sampling rate?

Many thanks for you info.

Comments

  • EricEric
    1. The IMU can measure motion on the order of inches.  Be aware that MetaMotion boards cannot directly communicate with each other and don't have any proximity sensors so relying on solely IMU data may be an impossible task.
    2. Check out the tips outlined in this blog post.  Timestamps will never be exactly aligned across multiple sensors however the sensors are very accurate with their timings.
    3. You can use the filters to determine if a sample of data should be logged though that depends on what "intelligently filter data" means.  Since you mention using sensor fusion however, you cannot operate the sensors at 800Hz so perhaps this is a moot point.
    4. You cannot log data from that many sensors at once.  You can choose from acc + gyro + mag, 2 sensor fusion outputs, or 1 sensor fusion output + any 2 of acc/gyro/mag.
      The logger does not synchronize log entries from multiple data sources.  Each sensor has its own records though again, these sensors have very accurate timing.
    5. Sensor fusion only runs at 25Hz, 50Hz, or 100Hz and will most likely drain the 100mAh battery in a few days.
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