FDC1004: Working principle of FDC1004 sensor and queries in output

Malathi Malathi

Prodigy 20 points

Part Number: FDC1004

Need some clarification in the below queries.

We used a spherical container for liquid level detection using FDC1004 board. We are getting a graph like below. while water level is decreasing suddenly capacitance is increasing (suddenly PF jumps from one pf to another pf ex: 2pf to 5pf in 200ms) and this effect is occurring in a range of every 27pf (refer graph).

1. We are suspecting this effect could be because of the offset and gain calibration circuit inside FDC or any other calibration programming/algorithm inside FDC. Correct us if we wrong.
2. If this effect is due to above Point a whether this can be avoidable using any programming.

What is the capacitance charging current of FDC1004.
Need more information on the Capacitance to digital converter in block diagram. Is there any filtering circuit is creating the above mentioned issue.

3 months ago

0 John Miller - Sensing 3 months ago

TI__Mastermind 33270 points

Malathi,

The nominal capacitance range for the FDC1004 is ±15pF.
Beyond that range, you need to use the CAPDAC to create an offset.

Are you doing that in your application?

regards,
John

0 Malathi Malathi 3 months ago in reply to John Miller - Sensing

Prodigy 20 points

Yes we are using CAPDAC for our application

0 John Miller - Sensing 3 months ago in reply to Malathi Malathi

TI__Mastermind 33270 points

Malathi,

Device internal offsets and gains are calibrated in production.

If you raise and lower the liquid level several in succession, does the step always occur in the same place, or does its location change with respect to the liquid level?

Regards,
John

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FDC1004: Working principle of FDC1004 sensor and queries in output