physical properties coils evm 1614

Melanie Loy

Other Parts Discussed in Thread: LDC1614

Dear All,

is it possible to get the pysical properties of the two coils attached to channel 0 and channel 1 of the evm ldc1614 ?

Already known from the chapter about the sensors of the evm in the manual is that the coils has 14 mm diameter , 32 turns and 2 layers .

There are also some plots in the same chapter for which it would be great to get an example how to use them to calculate the register values if possible.

My guess is that you select the frequency of the sensor and take the value for L , Q and Rs out of the plots and calculate everything else from there. Is this correct ?

In the data sheet for the LDC1614 there are plots for a coil with 14 mm diameter , 32 turns 2 layers which was designed for a 1,5 mm thick Aluminum target.

Is it the same coil like the ones attached to the evm ldc 1614 ?

I want to have the data to be able to do the similar thing to the example set up of the ldc in the data sheet. There another coil is used.

The last question I have for know is for which target exactly are the coils designed ?

Thanks for your support in advance.

BR,

Melanie

over 8 years ago

0 Chris Oberhauser66 over 8 years ago

TI__Genius 14270 points

Hi Melanie,

The coils are 1oz Cu manufactured on a 1.6mm thick FR4 PCB. Note there are two revisions of the EVM. On the bottom, if you see the number SV601126A, then you have the Rev A EVM. Rev A EVMs have a trace thickness of 4mil and a separation of 4mil. If the number on the bottom is SV601126B, then the trace width and space is 6mil ( 0.15mm).

The reported data in the datasheet uses the Rev A EVM sensors.

There are two different EVM user guides, one for each version (www.ti.com.cn/.../snou133.pdf for Rev A, www.ti.com/.../snou135.pdf for rev B).

Please look at http://www.ti.com/lit/snoa930 for more information on designing a sensor.

Inductive sensors are flexible in the target characteristics - the sensor frequency for the rev B is approx. 3MHz. The thickness of the target should be at least 3 skin depths, and the physical size of the target should be >80% of the target diameter. Note that your system may not be able to use a target of that size; in that case you will get a reduction in the response, but you may not have an issue in your system.

Regards,

ChrisO

0 Melanie Loy over 8 years ago in reply to Chris Oberhauser66

Prodigy 80 points

Hi Chris,

thanks for your quick reply. The info regarding the coil properties and the size of the target was quite helpful.
I found out that I have the Rev A EVMs. It's also good to know that the data in the datasheet is really for the same coil.

Some hinds from your side for configuring the LDC1614 with the help of the plots on page 16 and 17 on in manual
for Rev A would be great.

I would like to use 4 coils from Rev A EVM on the LDC1614 and I want to use the internal oscillator as well as the INTB Pin
to know when I have valid data on all channels to poll the data. Let's assume target e.g. a 2 Euro coin. Distance and resolution
just for getting the idea 0.1 cm and 02 um like in the example in the data sheet. I just named random conditions for an example to
get the idea how it works.

First thing I would do then is look into Figure 21 on page 16 of the manual and select a fsensor in a way that I have a low Rs.
For example 2 or 3 MHz . Then I would look into Figure 22 on page 17 and get the Q value for the same frequency.
Then I could calculate my Rp value with the help of the Formula for calculating Q on page 37 of the data sheet of the LDC1614.
After that I need to configure the registers with the help of the formulas of the data sheet. In a way similar to what's done
in the data sheet on page 40 and 41.
Is this the right way to proceed or do I still miss a point ?

I'll look into the info you'll named for designing sensors never the less.

Thanks for your support in advance.

BR,
Melanie

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