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FDC2114: reading calculation

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Replies: 7

Views: 67

Part Number: FDC2114

Hi

May i know where can i find the reading calculation into PF in which document?

  • Hello,

    Please use equation 8 in the FDC2114 datasheet.

    Best Regards,

    Kristin Jones

    Current and Position Sensing

    Applications Engineer

    For more information, check out the Inductive Sensing FAQ

  • In reply to Kristin Jones93:

    thanks a lot 

    may i know the result units in pf or nf?

  • In reply to Aoday:

    Hello,

    The units are in Farads, assuming you enter the inductance in H and the frequency in Hz.

    Best Regards,

    Kristin Jones

    Current and Position Sensing

    Applications Engineer

    For more information, check out the Inductive Sensing FAQ

  • In reply to Kristin Jones93:

    Dear Kristin

    i am a bit confused if we consider that the frequency is 40 Mhz and L=18uH wher c=33pF and if we consider the DATAx = 1 and the CHx_FIN_SEL=b01. the calculation as folows:

    Fsensor =(CHx_Fin_Sel*Frefx*DATAx)/2^28

                  =(2 * 40*10^6 * 1)/2^28 =0.298  is it correct?

    and 

    Csensor= 1/(L * (2*pi*Fsensorx)^2) - C

                = 1/( 18 * 10^-6 *(2 * pi * 0.298)^2)  - 33 pF   is it correct?

     

     

  • In reply to Aoday:

    Hello Aoday,

    Can you clarify if you are using the FDC2114 or the FDC2214? If you are using the FDC2114 (like you've tagged in your post), then you are using the wrong equation in your calculations above. You've used equation 9, which is only applicable to the FDC2214. You would need to use Equation 8.

    Also please note that a DATAx value of 1 is not possible, because 0.298Hz is lower than the 10kHz sensor frequency minimum. You will get much more reasonable numbers if you use a sample DATAx value from the GUI.

    Best Regards,

    Kristin Jones

    Current and Position Sensing

    Applications Engineer

    For more information, check out the Inductive Sensing FAQ

  • In reply to Kristin Jones93:

    sorry the part no. is FDC2212

    YES I CALCULATED BUT NOW MY QUESTION is is it correct using the frefx 40 Mhz? and the chx_fin=2?

    because now the total capacitor is about 11 pf before i minuse it from 33 that is mean it will be in negative 

  • In reply to Aoday:

    Hello Aoday,

    If you are using an external 40MHz oscillator (the default on the EVM) and you have configured the CH0_FIN_DIVIDER to 2, then yes, those are the correct values to use in the equation. 

    Best Regards,

    Kristin Jones

    Current and Position Sensing

    Applications Engineer

    For more information, check out the Inductive Sensing FAQ