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ADS1262EVM-PDK: Load cell signal sampled with the ADS1262

user5834775
Prodigy 220 points

Part Number: ADS1262EVM-PDK

Hello 

I have a doubt about the sampling signal sampled with my ADS1262. I'm sampling a load cell signal for the different frequencies of the ADS1262, and I am obtaining the next result. (Note: the value of the result are in kg).

It is observed a sinusoidal signal with a frequency of 50Hz for all the sampling frequencies. What is it due to? Could be it electric noise coupled to the load cell signal  or is it something of the ADC sampling?

The ADS1262 is configured with a gain of 32 V/V and a sinc4 filter. The ADC is powered with an external power supply where AVDD=5V and AVSS=GND. Moreover, VREF(+)=5V and VREF(-)=GND. The ADS1262 is connected in ratiometric way with the load cell. 

Thank you in advance.

Best regards.

  • 0
    TI__Mastermind 44680 points

    Hi,

    I'm not sure I understand the issue...

    When measuring a 50 Hz signal at 400 SPS, you'll have 400/50 ≈ 8 samples per period. At the 4800 SPS data rate you'll sample the 50 Hz signal about 96 times per period. And at 14.4 kSPS you'll have ~288 samples per period. The signals you plotted all appear to show an intact 50 Hz signal.

    Noise performance at the higher data rates will be worse, as expected. Higher data rates allow for a wider signal (and noise) bandwidth to be sampled and the digital filter of the ADS1262 will not reject as much noise at the higher data rates. Therefore, I would expect the additional noise on the 14,4 kSPS plot.

    Is there some other characteristic of the measured signals that appears to be incorrect?

  • 0 in reply to Christopher Hall
    Prodigy 220 points

    Hi,

    Thank you for the response. All is solved. The problem was that the signal not should be of 50Hz, and my question was if this 50 Hz signal was electric noise coupled to the real signal or was caused for some reason for the ADC.

    Best regards.

  • 0 in reply to user5834775
    TI__Mastermind 44680 points

    OK, I'm sorry for my misunderstanding.

    Most likely a 50 Hz signal would be noise coupling into the system one way or another. In addition to finding and removing the coupling source/mechanism, you can always configure the ADS1262 to operate at a data rate that places a digital filter notch at 50 Hz (or 50 & 60 Hz) to help reject power line cycle frequencies.