FDC1004EVM: FDC1004EVM sensitivity changes depending on the computer I'm using

Alex Semeniuk

Part Number: FDC1004EVM
Other Parts Discussed in Thread: FDC2214EVM

Hello TI community,

I've noticed that my FDC1004evm and fdc2214evm show different sensitivity(i.e. signal to noise ratio) depending if they are connected to a desktop or to a plugged in laptop.

Due to the nature of my experiment I need to use around 1 m long coax cables and about 2 m long usb extension cords. The plates are 2''x2''.

it looks like the noise band becomes larger ( which decreasing sensitivity) with laptop that with a desktop,while the absolute capacitance remains almost.

After looking through some earlier posts I've tried using ferrite beads on usb cable, but that didn't help.

Would you please suggest any solutions?

Thank you in advance,

Alex

over 7 years ago

0 Kristin Jones93 over 7 years ago

TI__Genius 17440 points

Hi Alex,

The biggest difference between the two setups is how the EVMs are grounded. I would suggest connecting the EVMs to a larger ground plane and seeing if that makes a difference. Although the ground shifting app note is not about the issue you are having, section 3 shows the type of larger ground plane I am suggesting.

Regards,

0 Alex Semeniuk over 7 years ago in reply to Kristin Jones93

Intellectual 300 points

Hello Kristin,

Thank you for your suggestion.
Is it crucial to have a grounding plate under the sensor plate or
I could ground EVM to a roll of a copper tape siting somewhere aside?

Thank you,
Alex

0 Kristin Jones93 over 7 years ago in reply to Alex Semeniuk

TI__Genius 17440 points

Hi Alex,

My apologies for the delayed response. The orientation should not matter, just the presence of a large, uninterrupted ground plane. Your higher frequency signals are likely causing the issue, so a thin ground plan should work as well.

Regards,

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FDC1004EVM: FDC1004EVM sensitivity changes depending on the computer I'm using