Estimate inductance change caused by the target

Andreas H

Hi,

I wondered how I could estimate the change of inductance of a sensor coil, which happens when a target is placed near the coil.

Are there some approximation methods available, or how can this be done using the field equations, e.g. by calculating the induced eddy currents?

Thank you very much for your help!

over 7 years ago

0 Luke LaPointe over 7 years ago

TI__Genius 13335 points

Hello Andreas,
Please refer to the "Inductive Sensing Design Calculator Tool" :www.ti.com/.../slyc137
The far right tab titled "Racetrack_Inductor_Designer" has the ability to enter in the metal-to-sensor distance and gives the corresponding approximated inductance value.
Regards,
Luke

0 Andreas H over 7 years ago in reply to Luke LaPointe

Prodigy 160 points

Hello Mr. LaPointe,

thank you very much for this hint, that helped me a lot!

Could you maybe provide some literature, about how this change in inductance is calculated?

Thanks and best regards,

Andreas

0 Luke LaPointe over 7 years ago in reply to Andreas H

TI__Genius 13335 points

Hello Andreas,
We provide a lot of plots that show inductance vs distance. For example, please refer to page 14 of the Sensor Design Application Note: www.ti.com/.../snoa930.pdf
For specific coil designs you may want to simulate the inductance with a FEM simulator or momentum based simulation. Free tools such as FEMM exist: www.femm.info/.../HomePage
Regards,
Luke

0 Andreas H over 7 years ago in reply to Luke LaPointe

Prodigy 160 points

Hello Mr. LaPointe,

thank you for those links, I've simulated a simple coil-target-arrangement and the results match the approximation in the excel file in some degree.

Do you have some additional sources that can be used as reference to verify the results, e.g. the theory behind those excel calculations (a source for those approximations)?

Thanks and best regards,

Andreas

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Estimate inductance change caused by the target