OpenMarine
MPU-9250 Values Multiplier Wrong - Printable Version

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MPU-9250 Values Multiplier Wrong - feudalkaos - 10-04-2018

I installed and configured a new MPU-9250. I leveled the boat and pressed boat level in OpenPlotter. I am currently running version 1.2.0 alpha of Openplotter.

I am seeing values from the MPU-9250 but they seem to be off by a factor of 10. For example, right now I am showing 0.1 degree to starboard. When I compare this to my calibrated digital level on my phone as well as another phone they both show around 1 degree to starboard. 

When I lean the boat to what I believe is closer to 5 degrees based on my inclinometer and the two phones, OpenCPN shows about 0.5 degrees. 

I have checked in the SK Diagnostic windows on Openplotter and it appears the same as in OpenCPN.

This appears to be the case for Pitch as well.

Any advice would be helpful. Did I set something up incorrectly?


RE: MPU-9250 Values Multiplier Wrong - seandepagnier - 10-08-2018

Could you plot the raw sensor values using signalk_scope_wx?

Look at the accelerometer values.

A lot of mpu9250 are faulty for whatever reason, broken axes, non-biased etc.. Where did you get your sensors from?


You may need to calibrate the accelerometer.


RE: MPU-9250 Values Multiplier Wrong - feudalkaos - 10-08-2018

(10-08-2018, 10:13 AM)seandepagnier Wrote: Could you plot the raw sensor values using signalk_scope_wx?

Look at the accelerometer values.

A lot of mpu9250 are faulty for whatever reason, broken axes, non-biased etc..   Where did you get your sensors from?


You may need to calibrate the accelerometer.

Since it will not let me attach an image here is a link to a screenshot of the scope on the accelerometer. https://drive.google.com/open?id=1db5QhCE94M7l9jBkltAfAfjfs8uI_p08 This is with the boat rocking back and forth to about a 3 degree heel.

Here is another screenshot with the Heel value added. https://drive.google.com/open?id=12TA95tffBPpcq_ods1wNvBKisj1_1-Fe This was more like a 4-5 degree heel when rocking. You can see that the heel value is changing and it corresponds with the correct direction of motion but the value is less then the actual movement. The upper spikes in this image show the heel at around 0.5.

This is the one that I purchased https://www.amazon.com/gp/product/B01I1J0Z7Y/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1

It is responding to movement in the correct directions, it just seems like it is not as much as it should be. When I am expecting 2 or 3 degrees, it is showing 0.2 or 0.3. 

I did the "Boat Level" function in Openplotter. I have not taken the boat out and done circles to calibrate the compass yet but I have set the offset for it. I wasnt sure if this somehow would affect the accelerometer but I dont think it should.

Thanks for looking and offering advise!