Hello Viktorija,
"Does the LDC1000 EVM board allow for external sensors to be created and used without having to lay out new hardware on the board?"
Yes it does. You can snap the coil portion of the LDC1000 EVM off at the perforation and connect your own LC tank to the header J2. The EVM user guide contains more information. You can find it on www.ti.com/ldc.
"Could the inductive coils be placed on a cable with maybe 2 to 3 feet in length? How much would that affect the reading, if any?"
Yes, this is possible to connect the LC tank remotely after several feet of cable.
Please be aware that the additional cable length
- adds capacitance which affects tank oscillation frequency.
- reduces Q of the tank
- may have an effect on EMI, so depending on your system, special EMI reduction techniques may be required.
"If the coils were potted in a non-conductive potting, would this effect the readings at all?"
No, non-conductive potting will have no effect on readings.
"Unlike the image below, would it be possible to have a uniform metallic float with a non-uniform coil to generate the same output"
Yes, you can lay out the coil to produce a non-homogeneous EM-field and use a uniform conductive target such as a rectangle. This image shows an example of a coil that produces a non-homogeneous EM-field which can be used for lateral position sensing of a rectangular target:
