Hi Charles,
I took a few days to reply because I ordered a second development board. My results are similar to those reported by Liviu. For my new board both the coil that comes with the dev. kit and discrete tank circuits work good. Next I went back to the original board which has problems. What I learned was that the board was fine. The coil/capacitor associated with that 1st board does not work. I have rechecked the solder joints and the behavior does not change.
For my application I plan to hand build a coil ~75mm in diameter. Can you provide me an application note for setting up the LDC1000EVM using my impedance measurements (configuration page)? If you have any additional information on building larger air loop coils to work well with the LDC1000 that would also be helpful. My present understanding is that:
a) resonant frequency should stay between 1-5MHz, but it can go as low as 5KHz
b) RP must stay between 800-4MOhm
c) Parallel capacitor 20pF-100nF
I appreciate the help, Jeff