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FDC1004: Question with wiring Out-of-Phase Liquid Level

Kulatuch Suwattanapunkul
Prodigy 50 points
Part Number: FDC1004

Hi,

I tried to set up the shield as show in this "/lit/an/snoa925/snoa925.pdf" document. I'm not using FDC1004EVM but using Raspberry Pi instead. I achieved reading the value from sensor, but the problem is that I can't seem to find 

According to this image, I'm doubt about how to wire SHLD2. Is the wire connect to SHLD2 and GND is the same one, this probably mean that GND port and SHLD2 port are connecting to each other, do I understand right? If it's not, could you please let me know how to achieve the wiring of GND and SHLD2, with detail screenshot will be very helpful.

Thank you.

  • 0
    TI__Genius 17440 points

    Hi Kulatuch,

    SHLD2 and GND are not connected to each other. Here we recommend using a shielded cable for SHLD2, where GND is shielding SHLD2. In the middle part of the diagram, you can see that we also recommend using shielded cables for CIN2 and CIN1. In this case SHLD1 is shielding CIN1 and CIN2. 

    The SHLDx pins will be driven with DC voltages, so you should not connect them to the GND pin. You can read more about the function of the FDC1004's shield in section 8.3.1 of the datasheet.

    Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 50 points

    Thank you Kristin

    I found the note at the bottom of the experiment

    "Water is the liquid used in this experiment. Liquids that cannot be used for liquid-level sensing include oil-based liquids, soap, or a liquid with a sticky or slick residue."

    Can FDC1004 be used to measured the waste water level with OOP solution? If not, why?

  • 0 in reply to Kulatuch Suwattanapunkul
    TI__Genius 17440 points

    Hi Kulatuch,

    If the waste water will not leave a residue, or if the level detection does not need to be highly accurate, you could use capacitive liquid-level sensing. 

    Any residue left by the liquid will affect the capacitance reading of the sensors, which will over-report the fill level of the container. If the liquid is somewhat conductive (even soap is conductive enough), the liquid can discharge the sensor before it completes the capacitance reading, which will significantly decrease the system accuracy. 

    Regards,