FDC2212: How to calculate frequency for capacitance level sensing

sourabh tokikar

Part Number: FDC2212
Other Parts Discussed in Thread: LM555, FDC2214

Good morning

How the exciting frequency is determined for capacitance level sensor. How we can calculate the frequency with theoretical calculation also, sir if there any calculation theory is present for capacitance level sensor I Will be very thankful to you sir.

Regards

Sourabh

over 6 years ago

0 Bala Ravi over 6 years ago

TI__Expert 6625 points

Hi Sourabh,
You can use the formula, Fsensor = 1/(2*pi*(sqrt(L*C))). You can find this in section 10.2.3.2 of the datasheet. This formula can give you an approximation, but due to some parasitic capacitance from the design or from the PCB trace, the value may slightly differ. We also have an useful app note on performance analysis for liquid level sensing: www.ti.com/.../snoa935.

Best Regards,
Bala Ravi

0 sourabh tokikar over 6 years ago in reply to Bala Ravi

Prodigy 140 points

Thanks for sharing this information. But my question is if I am not using fdc series ic or simple lm555 timer or any other discreet analog based oscillator.

0 Bala Ravi over 6 years ago in reply to sourabh tokikar

TI__Expert 6625 points

Hi Sourabh,
You tagged FDC2214, so I assumed you were referring to FDC series. We do not support LM555 timers, but you may find the following app note useful:
1. Out-of-Phase Liquid Level Technique - www.ti.com/.../snoa925
2. Direct vs Remote Liquid Level sensing analysis: www.ti.com/.../snoa935
3. Liquid Level Sensing with Immersive straw approach: www.ti.com/.../snoa934

Best Regards,
Bala Ravi

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FDC2212: How to calculate frequency for capacitance level sensing