Distance Measurement!

Im looking forward to measure distance of about 0 to 15 feet and implementing RF modules and then using a KEYFOB whcih consists of the NORDIC TRANSCEIVER NRF24L01+ ,leaving the GPS can anyother option is there which can be implemented to measure the distance noting the KeyFob is this one >> that is pretty small to accommodate any other module in it,

can RF ID be a solution? but its reading range is pretty less that is in centimeters?!! i think if a cost effective RF ID tag then things WILL work up for me.

Im looking forward to measure distance of about 0 to 15 feet

Measure distance between what?

Please tell us more about exactly what you want to do.

Hi terry,

Im in need of measuring distance between two rf modules and the ones I have shortlisted is rfm70 which has received signal strength indicator in it and the other the Nordic nrf24l01+ module any one of these has to be used and then a pair would be ordered , I already have the rfm70.

Will there be sufficient resolution in received signal strength to get a meaningful distance measurement? A quick google for rssi accuracy suggests not.

I know that but that's only co option because given the key fob from spark fun in eyeing one cannot fit another thing in it or stick something outside leaving only the option of rf id tag

I think you need to get this set up with the RSSI (Received Signal Strength Indication) being displayed on Serial Monitor etc.

Over this range you MIGHT be able to calibrate this as distance VS RSSI.


  • Signal strength will change with the square of the distance, not linearly
  • Signal strength will be quite antenna and environment sensitive
  • RSSI is probably logarithmic in response

You'll need to try this out and see if it can be accurate enough for your purpose.

@terry yes.thanks is there a how to that one can use the rssi on these Nordic modules?