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FDC1004EVM: Longer Sensor Length for PVC Tank

Sami Dhaou
Prodigy 85 points
Part Number: FDC1004EVM
Other Parts Discussed in Thread: FDC1004

Hi,

I am using the FDC1004 evm with reference design TIDA00317 for measuring level from a container. 

With an electrode length of 100mm for a small contrainer worked well for me. I used Out-of-phase technique for the measurements. The measurements were ranging from 2pf to 7.8pF where 2pF was for empty container and 7.8 for full.

But I need to use a bigger PVC container with length of 180mm and 4.9mm thick and the measurement should cover whole length of the container. For this I need to modify the reference design.

Could you suggest me a solution for this problem?

Should I need to increase the length or width of the electrode? 

or is there anything else that I need to take in to consideration before modifying the reference design?

Regards,

Sami dhaou 

  • 0
    TI__Expert 6480 points
    Hi Sami,

    How thick were the walls of the smaller container? What is the distance between your level electrodes?
    If you want to measure the whole length of the bigger container, you will need to increase the length of your sensors from 100mm to 180mm. In order to compensate for thickness, you may need to increase the width of your sensors and the spacing between them to be about 2x the thickness of your container.

    Thanks,
    Rachel
  • 0 in reply to Rachel Liao
    Prodigy 85 points
    Hi,
    thank you very much Rachel for your answer.

    I use smaller container with 2.5mm thick.the distance between the level electrode is 4mm.

    I don't understand how can i compensate the thickness if i increase the width and the spacing betwenn them,is ther any formula to find the compensation factor?

    Regards,
    Sami
  • 0 in reply to Sami Dhaou
    Prodigy 85 points

    Hi,
    thank you very much Rachel for your answer.

    I use smaller container with 2.5mm thick.the distance between the level electrode is 4mm.

    I don't understand how can i compensate the thickness if i increase the width and the spacing between them,is there any formula to find the compensation factor?

    My project is in blocked state due to this issue and I need to solve this problem as soon as possible. 

    Could you please help me with this?


    Regards,
    Sami

  • 0 in reply to Sami Dhaou
    TI__Expert 6480 points
    Hi Sami,

    Apologies for the delay - unfortunately, we do not have any formula to find a compensation factor. Since we are measuring fringing fields between two electrodes, the fringing fields need to penetrate through the thickness of the wall. A general rule of thumb we use is that the width between the sensors should be roughly twice the thickness of the container.

    Thanks,
    Rachel
  • 0 in reply to Rachel Liao
    Prodigy 85 points
    Hi,
    thank you very much Rachel for your answer.
    I will try and i tell you if all ok .

    Regards,
    Sami