LDC1612EVM: Sinusoidal drift while reading data from sensor coil of 50 turns of 22 gauge copper wire

Mahesh J Shetty

Part Number: LDC1612EVM

We are working on a project to measure the angle of a metal flap inside the plastic tube where copper coil is winded outside the pipe and at first we were working with 900 turns,36 gauge copper coil where the drift was almost negligible but when started to work with 50 turns, 22 gauge copper coil the inductance value is drifting like sinusoidal(decreasing and increasing randomly). we are using only channel 0 and metal we used as a flap is stainless steel. please help me regarding the problem and with possible solution.

over 5 years ago

0 Clancy Soehren over 5 years ago

TI__Mastermind 23810 points

Mahesh,

You should first measure the properties of your sensor, including L, Rp, and Q. This will verify that you are in the correct operating range.

From there, it is possible that your IDRIVE setting is off, which could cause more noise in your system. You can refer to this app note for tips on this setting:

www.ti.com/.../snoa930a.pdf

This sensor design app note will help you understand your sensor properties:

www.ti.com/.../snoa930a.pdf

0 Mahesh J Shetty over 5 years ago in reply to Clancy Soehren

Prodigy 100 points

Thank you Clancy Soehren for your reply and suggestion. I will measure the things and will look through the pdf you mentioned and will reply regarding the test.

Thank you.

0 Mahesh J Shetty over 5 years ago in reply to Clancy Soehren

Prodigy 100 points

Clancy Soehren how to select capacitance value for our inductance sensor?

0 Clancy Soehren over 5 years ago in reply to Mahesh J Shetty

TI__Mastermind 23810 points

Mahesh,

There is quite a big of flexibility for the exact inductance and capacitance values. Here are a few tips:

- The capacitor should be greater than 100pF if possible to avoid parasitic effects.
- The best resolution occurs between 400kHz and 6MHz, so you can choose the capacitor to stay in this region.
- The skin depth of your target is important as described in this app note. Choose a higher frequency to help with this:

www.ti.com/.../snoa957

There is a also a small section in the sensor design guide I linked earlier about choosing a capacitor.

0 Mahesh J Shetty over 5 years ago in reply to Clancy Soehren

Prodigy 100 points

Thank you, it helped me a lot.

Sensors

Sensors forum

LDC1612EVM: Sinusoidal drift while reading data from sensor coil of 50 turns of 22 gauge copper wire