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ADS1258 and harmonics

Mostafa Elwakeel
Prodigy 105 points
Other Parts Discussed in Thread: ADS1258, INA128

Hi All,

i design new ECG machine using ADS1258 . usually ECG signal is 1 mV .

i used the EVM of ADS1258 and i had buffer board and anti-aliasing filter and instrumentation amplifier INA128.

the problem is the are harmonics for 50 HZ and had very large values so i cant filter the signal and i don't know from where this harmonics come ???

Can any one help me ??

Thank you

  • 0
    TI__Mastermind 43915 points

    Sounds like you are picking up something externally. European power sources run off of 50 Hz (60 Hz in the US), so your input may be picking up something. This can be coming into your system from the lights or even your probe. You can try shielding your inputs, turning off all external equipment around the device that is not used, or creating a high pass filter to see if it minimizes harmonics at 50Hz. 

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Prodigy 105 points

    Hello Tony ,

    Thanks for your reply .

    but i think the problem in ADC itself .

    becouse  we measure before the input of the adc directly and we dont see any harmonics in input .we change equipments and testing lab and area and make good shielding . and no change of the results

      so what do you think ?? what makes this effect other than pick up noise form out side source .  how we can solve this problem ??

    Thank you for your help

    Mostafa

  • 0 in reply to Mostafa Elwakeel
    TI__Mastermind 43915 points

    Mostafa,

    What specifically is your test set up? What is your frequency of input? If you are measuring DC you should be able to put a highpass filter at the input.

    How are you measuring the input signals to verify their is not 50Hz present? Have you short circuited the two inputs together and looked at the output harmonics?

    What size signal are you measuring at your input?

    Can I see a schematic of your setup.

     

    Regards,

    Tony