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FDC2214 - initial calibration

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: FDC2214EVM, FDC2214, FDC2212

Hello,

Could you please let me know the initial calibration method for water level sensor?

In the customer, the 0cm measurement value is varied each time.
I think that this reason is the moisture and ball of water.

In the datasheet figure 56, three sensors are used for calibration.
They are evaluating this application by FDC2214EVM however the customer would like to use only 1~2ch.
They will change the device from FDC2214 to FDC2212.

Best Regards,
Ryuji Asaka

  • 0
    TI__Expert 8050 points
    Hi Asaka-san,

    Moisture and droplets of water can affect 0cm measurement. Other causes include temperature drift, movement of sensor/setup between measurements, or even the presence of human or objects. For example, there could be some slight shift in the setup depending on how the container was emptied.

    In some cases, if the reference sensor was too small, it could cause more variation in the data.

    Depending on the application, the env sensor may not be needed. The customer can replace CRE with CRL(0) in the level equation to calculate liquid level height.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Guru 20090 points
    Hello Yibo san,

    Thank you for the reply.
    Could you please let me know more detail of the following?
    " The customer can replace CRE with CRL(0) in the level equation to calculate liquid level height."

    Currently, our customer use 1cm of CRE on the Ch0 and 110cm of CRL(1) on the Ch1
    1cm of CRE is no meaning in the customer application.

    In the datasheet,
    Level = href * (Clev-Clev(0))/(CRL-CRE)

    We can replace the CRE with CRL(0).
    Then,
    ---> Level =href * (Clev-Clev(0))/(CRL(1)-CRL(0)) ?
    Thus, should we use 110cm of CRL on the Ch0?

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    Guru 20090 points
    Hello Yibo san,

    Sorry for bothering you.
    However could you please let me have your reply?
    I will appreciate your help with this situation.

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Expert 8050 points
    Hello Asaka-san,

    Yes, that's the right idea. If there's no meaningful environmental change near the top of the container, then they can get rid of CRE and only uses two channels, one for CRL and the other for Clevel. The equation you wrote is correct for this case.

    Best regards,
    Yibo
  • 0 in reply to Yibo Yu
    Guru 20090 points

    Hello Yibo san,

    Thank you for the reply.
    Is the attached my understanding correct?



    Best Regards,
    Ryuji Asaka

  • 0 in reply to Ryuji
    TI__Expert 8050 points
    Hello Asaka-san,

    It's better to use two parallel sensor strips for each channel, as shown in this application note.
    www.ti.com/.../snoa935a.pdf

    Best regards,
    Yibo