resolution and L inf uH

Hello Florent,

"what is the resolution of the coil default on the evaluation kit. I want to make an angular measurement. How do I know that when the metal surface that covers it no longer does change because the surface is too small."

the EVM GUI shows 15 bits proximity data resolution and 24 bits inductance resolution.

"I have another problem, on my computer the value for inductance are inf uH all the time. If I clic on autoscale the software crashed. I can see the proximity data and the frequency"

From your question, I assume that you replaced the EVM LC tank with a custom LC tank. For debug purposes, please try the following:

• Does your LC tank oscillate? You can verify by checking that proximity data reading in the GUI changes when you move a piece of metal closer to the coil, or by connecting a scope probe to one of the pads in header J2 on the EVM and verifying that the LC tank oscillates. 
• Does your LC tank satisfy the requirements on RP and Fsensor as shown in question "What is the min/max inductance or min/max coil diameter which the LDC1000 can drive?" in the inductive sensing FAQ? http://e2e.ti.com/support/data_converters/inductive-sensing/f/938/t/295036.aspx
• Check if reducing the oscillation amplitude helps. You can change the oscillation amplitude by clicking 'stop' in the GUI streaming panel, and reducing 'LDC configuration: amplitude' in the configuration panel to 1V.
• Ensure that the sensor capacitor value in the top-left corner of the GUI reflects the capacitor of your LC tank.

By the way, which GUI revision are you using?

Hello,

i use the last version, it's the 1.0.4.0 something like that.

What's the sensitivity of the inductance, i want measure 360° , i can make a swirl but i'm not sure inductance can detect at the beginning of the swirl. Can i hope a angle measure sensitivity at 0.1°?

Thanks

Hello,

can i define the dead zone of a swirl with a pcb coil in the evaluation kit?

Thanks

Hello Florent,

angle measurement with 0.1% is feasible with a multi-coil design. However, we currently don't have any design guidelines and minimum size restrictions for such a system.

What are the physical arrangement and dimensions that you require in your system to measure rotation angle?

Hello Ben,

the maximum diameter of the swirl is 16mm. So the diameter of a coil is 8mm or less. Distance shall not exceed 4mm between the swirl and a coil. I think using 2 coils because the swirl have a dead zone,so i suppress the dead zone with the second coil.

Thank's

Thank you for letting me know. Unfortunately, we don't have design guidelines for such a system available at this point. Once we publish design guidelines for high precision angular sensing, they will be available on www.ti.com/ldc under 'Tech Docs'

Hello,

Is it possible to calculate the value of the coil if the coil is completely covered. This piece is located at a distance of 3.5mm (7mm diameter coil).

I know the initial value, the surface is s = pi*3.5² = 38.485mm² when the coil is completely covered.

the coil at a resolution of 24 bits, so for 1 bit i have : 38.485/(2^24) = 2.294 *10^-6 mm².

 if i have the coil value totally covered, i can find the sensitivity of the coil for my application.

Please :)

Hello Florent,

our Inductive Sensing Webench tool can simulate sensitivity vs distance for a large number of coils. Please check if it is helpful for your needs. You can find more information on Webench in our Inductive sensing FAQ question  "Can you help me to design a PCB coil?"

Hi Florent,

To add to this discussion, I would recommend avoiding 1.0.4.0 and use the latest version.  There were a few bugs that were patched from this version.

Thanks,