FDC1004: Initial Calibration Difficulties.

Thomas Gross56

Part Number: FDC1004

Hi Guys,

I am designing a capactivie sensor to measure liquid height based on the Out of Phase technique, SNOA925–January 2015.

I have written my own Arduino code to control the FDC1004 and it works well with both single ended and differential measurement although I am struggling to calibrate the device properly.

I understand that in differential mode the CAPDAC value should not affect the readings of my sensors but it has massive affect on my readings, up to tripling the values.

Changing the CAPDAC value also has the affect of making my reference sensor decrease in value, in certain ranges.

I have thoroughly read the FDC1004 datasheet but any additional calibration information would be very useful.

We want to go into manufacturing in the next 9 months so would really appreciate all help.

Thanks

Thomas

over 8 years ago

0 Yibo Yu over 8 years ago

TI__Expert 8050 points

Hi Thomas,

In your differential measurement, how did you set up the CHA and CHB of your measurement?

Regards,
Yibo

0 Thomas Gross56 over 8 years ago in reply to Yibo Yu

Prodigy 70 points

Hi Yibo,

I have it set up so Measurement 1 does CHA = 0, CHB = 3 and Measurement 2 does CHA = 1 and CHB = 3.

Thanks
Thomas

0 Thomas Gross56 over 8 years ago in reply to Thomas Gross56

Prodigy 70 points

Hi Yibo,

I have fixed the issue with the capdac, i believe we were setting its value wrong which was affecting the registers nearby.

Unfortunately I am still having issues with setting the gain and offset values. I am trying to measure 150mm of water but the capdac value saturates around 70mm so I believe i need a higher offset but changing the values seems to make no difference to my readings.

Thanks
Thomas

0 Yibo Yu over 8 years ago in reply to Thomas Gross56

TI__Expert 8050 points

Hi Thomas,

Please let us know if the offset is working as expected.

Regards,
Yibo

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FDC1004: Initial Calibration Difficulties.