Distance Measurement Accuracy

[ptejasv]

Hello and thank you for your help.

I am working with the nrf52840 for a project that uses distance estimates. I have tried the sample Bluetooth: nRF Distance Measurement with Bluetooth LE discovery using MCPD. Can I check if there are any accuracy estimates for the MCPD ranging mode or any tested margin of error? I would like to see if the measurements I am getting are within the expected range.

Thank you.

[Simonr]

I'm sorry, we don't have more concrete information than what is stated in the slides and the webinar itself on what exactly the environment was like. However it should be safe to assume the two DKs were placed on two desks in an open office environment with no metal obstacles directly inbetween them. Wifi and other BLE devices was likely not disabled.

What does this "metal measuring tape" do exactly in your setup? And what size is it?

Best regards,

Simon

[ptejasv]

Thank you.

The measuring tape is a standard aluminum tape I used as a reference for the actual distance. My setup is similar to the image below where the boards were on the floor. Removing the tape gives me slightly larger readings (around 9.4m for an actual distance of 6m compared to 9.1m with the tape).

Can I check if the method of configuring high precision was correct? I didn't modify any of the sample code for distance measurement except for setting CONFIG_DM_HIGH_PRECISION_CALC=y in the proj.conf file.

 Distance measurement sample used: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bluetooth/nrf_dm/README.html 

[Simonr]

Okay, I thought maybe you used it to try and block the signal, Can you confirm that the SDK version you're using for testing is v2.2.99 of the nRF Connect SDK, then I can ask the developers if there are any known issues with the version you're using? Enabling CONFIG_DM_HIGH_PRECISION_CALC in your project config file should be sufficient, but please note that the calculation has an impact on MCPD ranging only. Can you also try raising the two DKs from the floor by putting them on chairs or desks for example?

Best regards,

Simon

[ptejasv]

Yes, I am using v2.2.99. I tried putting the DKs on plastic stools, which helped slightly, but I think what really made a difference was placing the reflector on its side as in the setup from the webinar instead of having it flat. I'm getting readings within 0.5m of the actual distance today and that is sufficient for what I'm working on. Thank you for your help!