Title: Distance Measurement Shows Double the Actual Value on nRF52840

[Usha]

I am using an nRF52840 and  nrf52832 to measure distance, but the reported value is almost twice the actual distance. For example, when the actual distance is 1 meter, the reading is around 2 meters.

What could be causing this issue? Is there a setting or calibration step I need to adjust in the Nordic SDK?

I am currently working on this project and would appreciate a quick response.

[Usha]

I am measuring the distance between two devices placed 60 cm apart, but the reported distance fluctuates between 0.88 m and 1.43 m. What could be causing this variation, and how can I accurately calibrate the offset?

[Simonr]

Hi

It's a bit strange that it fluctuates by this much. Are you testing on two nRF52 DKs or custom boards? And can you share some details on what environment you're testing in? Are the devices in field of view of each other, and is there a lot of other activity on the 2.4GHz band in the space you're testing here? 

The zero distance calibration can also be done at 0cm, and the offset would be whatever the distance you see there that you will have to implement manually in your application so that the ranging result always adds/subtracts the offset before printing them to the terminal.

Best regards,

Simon

[Usha]

"I am measuring in an office environment, with both antennas facing opposite to each other."

[Simonr]

What do you mean by "both antennas facing opposite to each other"? As in away from one another?

Try putting the devices next to each other and see what the measured distance is then. That should give you less of a fluctuating distance and an idea of how much it should be calibrated with. With the 0.88-1.43m measurements it's hard to say as I don't know the median value or how often it reaches the minimum and maximum, but if it is an even spread/bell curve of measurements I guess the median value would be ~1.15m, meaning the calibration should be set to 0.55m so that the measurements will average ~60cm.

Best regards,

Simon