5 Replies Latest reply on Nov 12, 2020 9:26 PM by AH_96

    Maximum distance and Limitation of Capsense Proximity

    GiLi_1363751

      Hi there,

       

      I would like to know the limitation and maximum sensing distance of the capsense proximity sensing loop design.

      1. Is the sensing distance proportional to the size and trace width of the sensing loop?

      2. Is there any limitation about the sensing loop size?

       

      Thank you,

      Gilbert

        • 1. Re: Maximum distance and Limitation of Capsense Proximity
          GaneshD_41

          Hi Gilbert,

           

          I would like to know the limitation and maximum sensing distance of the capsense proximity sensing loop design.

          1. Is the sensing distance proportional to the size and trace width of the sensing loop?

          We would like to say that the limitation is not the sensing distance but the parasitic capacitance and change in parasitic capacitance of the proximity sensor. The recommended maximum parasitic capacitance of sensor is 200 pico farads. This is not a strict value as you can always do manual tuning of sensors.

           

          2. Is there any limitation about the sensing loop size?

           

          Again, there is no limitation in size. The limitation is due to parasitic capacitance and environmental noise factors.

           

          Thanks

          Ganesh

          • 2. Re: Maximum distance and Limitation of Capsense Proximity
            AH_96

            Hello Gilbert,

             

            The maximum evaluated sensing distance is 30 cm using proximity sensor. This was in a well tuned hardware with firmware filters enabled.

             

            The sensing distance is proportional to the size of the loop. Roughly, we can expect a sensing distance equal to the diameter in the case of circular loops and equal to the diagonal in the case of rectangular sensors. The trace width is recommended to be 1.5 mm as anything greater will only increase the Cp without any performance gains.


            What is the proximity sensing distance that you are targeting in your application? What is the size of the PCB?

            It is recommended to place the sensor loop around the periphery of the PCB so that you get maximum sensing distance. Note that a ground ring needs to be placed around the proximity sensor for noise reduction.


            Best regards,
            Hari

            • 4. Re: Maximum distance and Limitation of Capsense Proximity
              GiLi_1363751

              Hi Hari,

               

              Thanks for your info and detail explanation.

              I was thinking to create a proximity sensor for around 100cm distance with around 25cm diagonal.

              I am fine with the GND ring around the sensor, but you mentioned it probably can create up to 30cm, plus with a well tuned design. Do you have any detail about this type of design to get more detail understanding with it.

              Any additional concern I may need to pay attention? Please advise.

               

              Many thanks,

              Gilbert

              • 5. Re: Maximum distance and Limitation of Capsense Proximity
                AH_96

                Hello GiLi_1363751

                 

                A proximity sensing distance of 100 cm was not evaluated and cannot be guaranteed. It cannot be achieved with a 25 cm diagonal. You can refer section 10.Design Consideration to Achieve 30-cm Proximity-Sensing Distance in our AN Proximity Sensing with CapSense.

                 

                Best regards,
                Hari