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PGA970: Digital interface and Primary excitation sine wave questions

Piyusha
Prodigy 110 points
Part Number: PGA970

Hi,

I am currently working on PGA970 for its application in LVDT sensor. I have the following 2 questions.

1. We are currently using 10 kHz as the frequency of our primary excitation signal. What is the best/ optimum frequency to use? 

2. We are using SPI (where STM32 acts as the master) to read and write the internal memory of the PGA970. Am I correct with the understanding that I cannot connect to PGA970 directly to the PC ( and print the amplitude demodulated data on the HyperTerminal) using a USB cable directly because there is a discrepancy in the communication ports ?

Thank you,

Piyusha

  • 0
    TI__Mastermind 31655 points
    Hi Piyusha,

    1. The best frequency to use is really dependent on the LVDT sensor that you are using and the highest expected frequency of the measurement. The primary frequency should be at least 10x the highest frequency that will be measured, and increasing the frequency will improve performance in an ideal system, but there is a limit in actual use. A higher frequency will make the system more sensitive to parasitic capacitance. If you don't expect the measured signal to go above 1khz, then a 10khz primary frequency will work fine.

    2. There will need to be some interface between the PGA970 and the PC as well as some software to translate the SPI data to readable inputs. If you use the PGA970 evm as an interface you can use the GUI to display DEMOD data.

    Regards,