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Original question:

MSP430G2253: Capacitance measurement

FDC2214: Need to measure the Absolute Value for the capacitance in pF

Sujit Shinde
Prodigy 90 points
Part Number: FDC2214
Other Parts Discussed in Thread: FDC2114

Dear Team,

We have procured The MSP-CAPT-FR2633 : MSP CapTIvate MCU Development Kit.

We wanted to measure the RAW / Absolute capacitance value (in pF) using the capacitance sensor. 

But, using MSP-CAPT-FR2633, I guess we are only able to get the Percentage Change in capacitance and not the RAW / Absolute capacitance value.

While browsing through forum, I discovered below link, which suggests to go for  FDC2214 board for getting RAW / Absolute capacitance value (in pF).

Link: https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/713934?tisearch=e2e-sitesearch&keymatch=MSP430G2253

Hence we are planning to procure the following FDC2214 board to get the Absolute capacitance value (in pF). 

Link: https://www.ti.com/tool/FDC2214EVM 

 

Question 1) Can you please suggest whether this board FDC2214 is OK for our requirement or any updated board is available

                                  from TI for getting RAW / Absolute capacitance value (in pF).

                                 ==> What is the absolute capacitance value range in pF available per sensor ( Min to Max value in pF)

Question 2) Using this board FDC2214, what is the Maximum Sampling Rate that can be achieved ?

                               ==> What is the maximum sampling rate per second / per sensor that is achieved, known to you. 

                               The example image shown on "FDC2114 and FDC2214 EVM User’s Guide" on page number 26 shows sampling rate as 18 :

                                 "Samples/Second/Channel: 18.78"

                               Link: for above User guide : www.ti.com/.../snou138a.pdf

Would like to hear from you.

Thank you.

Sujit Shinde

  • 0
    TI__Genius 17440 points
    Hello Sujit,

    The FDC2214 can measure raw capacitance. The FDC2214 uses a resonant architecture, which is a different architecture than traditional charge-based capacitive sensing. You can read this blog post to learn more about the differences between the two architectures:

    The FDC2214 measures capacitance by measuring the resonant frequency of an LC tank sensor. When the sensor capacitance changes, so does the resonant frequency. For this reason the device does not have a minimum or maximum measurable capacitance; the device can make measurements as long as it can drive the sensor at its resonant frequency (at a minimum of 1kHz and a maximum of 10MHz).

    The FDC2214 has 28-bit resolution and a maximum sample rate of 4.08 ksps. The FDC2114 has 12-bit resolution and a maximum sample rate of 13.3 ksps. This can be configured with the SETTLECOUNT registers and RCOUNT registers (Reference Count in the GUI).

    Best Regards,