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ECG Amplitude less

Arun Kumar27
Intellectual 590 points
Other Parts Discussed in Thread: ADS1294R, MSP430BT5190, ADS1298

Hi,

We are interfacing ADS1294R with MSP430BT5190. Test signals are given from a simulator.

We are able to get the clean ECG waveform (250SPS, lowpower mode), but the amplitude of the waveform looks less.

For testing, we have given a Sine wave of 1Hz and 1mV, and the peak to peak amplitude we are getting for this is 12000.

Are we missing some configuration?

Thanks & regards

Arun

  • 0
    TI__Guru 66166 points
    Hello Arun,

    Welcome to our forum. To get started, could you please tell us what your device register settings are? This is important to know in order to calculate the LSB (least-significant bit) size of the ADS1294R, where 1 LSB (volts/code) = (2*Vref)/Gain / (2^24 - 1). 12000*LSB should equal the magnitude of your input signal.

    Best Regards,
  • 0 in reply to Ryan Andrews
    Intellectual 590 points
    Hi Ryan,

    Thanks for the response.

    Following are the register settings i am using.
    Config 1 = 0x46
    Config 2 = 0x20
    Config 3 = 0xEE
    Loff = 0xEF
    Ch1Set = 0x00
    Ch2Set = 0x00
    Ch3Set = 0x00
    Ch4Set = 0x00
    Config3 = 0x22

    Regards
    Arun
  • 0 in reply to Arun Kumar27
    TI__Guru 66166 points

    Thanks, Arun.

    With a 4-V reference and Gain = 6, your LSB size is 119.2nV. 119nV* 12000 codes peak to peak means that your input voltage amplitude was about 1.43mVpp.

    What is the common-mode of your input sine wave? For a 4-V reference, you must use a 5-V supply (+/-2.5V) for the ADS1298, so your input common-mode should be 0V. Also, are you driving the ADS1298 inputs differentially or single-ended (see Figure 50)?
     
    Best Regards,