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CCS/LDC1614: LDC1614

Ali El-Zaghal
Intellectual 280 points
Part Number: LDC1614


Tool/software: Code Composer Studio

Hi, 

I am working on LDC1614 with delfino79D to measure the gap between a coil and metalic surface, i made a function that depends on 20 inductance samples measured  at [0 to 19 mm] gap and used this function to measure the accurate gap using linear interpolation method.

When using the internal coils from the sensor PCB which have the same Capacitance, inductance, and resistance, i found that the error in the coil connected to CH0 is differ from the one connected to CH1.

Note that all configurations are the same for both two coils and also i measured the inductance and capacitance and also was identical for both LC sensors.

Finally i checked on all calculations in the code and it was also identical, the i have two questions here.

1- what is my problem here with the coil connected to CH0 !

2- in section ''7.3.4 Reference Clock'' in data sheet what does he mean by [ Each channel has a dedicated divider configuration.], is this when using different coils with different specifications or he mean what !!

  • 0
    TI__Genius 17440 points

    Hello,

    Can you clarify what you mean by error? Are you talking about an offset in the output data between channels, or are you seeing more noise on CH0?

    How have you connected the coils to the LDC? Are they on the same PCB or are they connected with wires? If there are connection differences (either in the routed traces or the wires) between the two sensors, this could contribute to differences in the output data. 

    Can you also share how you measured the inductance and the capacitance?

    Section 7.3.4 of the datasheet is referring to the CLOCK_DIVIDERSx registers. They are used to reduce the frequency of F_sensor or F_ref before they are used in the sensor frequency measurement block. Unless you have changed these registers from their default settings, they won't contribute to differences between channels. 

    Best Regards,

  • 0 in reply to Kristin Jones93
    Intellectual 280 points

    Hi,

    I mean by "error" the shift in data reads from channels, also

    The circuits' connections are the same for both CH0 and CH1 [both are in the same PCB of the sensor], also

    Using LCmeter i measured the inductance of both two coils to be 20 Micro Henry, and also the capacitance but when i measured the capacitance for both two coils it was 500 nF, but in the PCB layout in sensor data sheet it was 330pF what is this mean !

  • 0 in reply to Ali El-Zaghal
    TI__Genius 17440 points

    Hello,

    Can you clarify if you are measuring the capacitance of the coil itself or the capacitance of the parallel SMD capacitor? It would be helpful if you could share your schematic. Please also probe the INxA/INxB pins with an oscilloscope and share a screenshot of the sensor oscillations.

    The capacitor used in the LC tank example in the datasheet was 330pF, but this is a very flexible value. You can use a significantly different value in your circuit, though 500nF is very high. I recommend a value between 100pF to 1nF. 

    Best Regards,