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Proximity Data out range

Joris De Beer
Prodigy 80 points

Hello,

My application uses a ferrite core coil of 680uH and a capacitor of 33nF. (Rs = 2.3 ohm; fsensor = 33kHz).

When I increase the RP_Min register, the Proximity data goes out range. 

And when I set the RP_min to the minimum value of 0.798kohm, the proximity data isn't stable.

Unstable measurement:

Measurement out of range: (no change when covering with conductive target)

What am i doing wrong? 

Thanks,

Joris.

  • 0
    TI__Genius 14270 points

    Hello Joris,

    There could be several things. Please make sure you are using a high-grade capacitor (C0G or NP0). When you report your Rs as 2.5ohms, is that at DC or is it the AC resistance? If it is the AC resistance, then it will be higher than the DC resistance; it is possible that your Rp is not what you think it is. If the Rp is too low (which is the same as the Rs being too high), then the LDC1000 cannot drive the coil

    Try increasing the RPmax setting in the GUI.

    Also, please make sure you set the Sensor Frequency value in the GUI properly.

    Finally, please make sure you are using the latest version of the GUI.

     

  • 0
    Prodigy 160 points

    Joris,

    It seems you have a problem with Q factor and resonant frequency. Please come back and precisely calculate it and adjust that factor.

    Thanks,

    Mammad