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ADS1292R: Problem with ECG output

Anur@g Tamboli
Intellectual 620 points
Part Number: ADS1292R
Other Parts Discussed in Thread: ADS1292

Hello, 

I am using ADS1292R for acquiring ECG from human body. But there is one problem which is persisting that ECG QRS complex changes its DC value. Any explanation will help. Thank you for your time.

Attached Picture of ECG. 

  • 0
    TI__Mastermind 38745 points
    Hello Anurag,

    This can be an issue sometimes when dc coupling dry electrodes. Make sure that the electrodes are firmly attached to the patient (you can utilize the ADS1292R's built-in lead-off detection functionality) and that you are using the right-leg drive functionality of this device.

    Brian Pisani
  • 0 in reply to Brian Pisani
    Intellectual 620 points
    Hello Brian,

    Yes i am using ADS1292R's right-leg drive functionality. I am using wet electrodes instead of dry electrodes. I have also attached hardware schematic for your reference.

    I didn't actually grasp what you meant by "dc coupling of dry electrodes".

    Thank you for your time.
  • 0 in reply to Anur@g Tamboli
    TI__Mastermind 38745 points
    Anurag,

    What I meant by dc coupling is a connection between the patient and the inputs to the device that does not include any high-pass filtering. For example, channel 1 uses a high-pass filter for the respiration measurement. Those inputs are ac coupled.

    Can you post your register settings here?

    Brian
  • 0 in reply to Brian Pisani
    Intellectual 620 points

    Yeah, Here you go.

    #define ADS1292_REG_ID 0x00
    #define ADS1292_REG_CONFIG1 0x01
    #define ADS1292_REG_CONFIG2 0x02
    #define ADS1292_REG_LOFF 0x03
    #define ADS1292_REG_CH1SET 0x04
    #define ADS1292_REG_CH2SET 0x05
    #define ADS1292_REG_RLDSENS 0x06
    #define ADS1292_REG_LOFFSENS 0x07
    #define ADS1292_REG_LOFFSTAT 0x08
    #define ADS1292_REG_RESP1 0x09
    #define ADS1292_REG_RESP2 0x0A

    ads1292_Reg_Write(ADS1292_REG_CONFIG1, 0b00000010);    
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_CONFIG2, 0b10110000); 
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_LOFF, 0b00010000); 
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_CH1SET, 0b00000000); 
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_CH2SET, 0b00000000); 
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_RLDSENS, 0b00101100); 
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_LOFFSENS, 0x00); 
    delay(10);
    //Skip register 8, LOFF Settings default
    ads1292_Reg_Write(ADS1292_REG_RESP1, 0b11110010); 
    delay(10);
    ads1292_Reg_Write(ADS1292_REG_RESP2, 0b00000011);

  • 0 in reply to Anur@g Tamboli
    TI__Mastermind 38745 points
    Hey Anurag,

    One thing I noticed is that you have bit 4 of the CONFIG2 register set. This bit enables the 4V internal reference, but should only be used if the internal reference buffer has enough headroom to create a 4V reference i.e. AVDD - AVSS = 5V. In your schematic, it looks like you are using a 3.3 V analog supply. If you clear that bit to use the internal 2.4 V reference, do things improve?

    Regards,
    Brian
  • 0 in reply to Brian Pisani
    Intellectual 620 points
    Hi Brian,

    I have changed it back to 3.3V reference. It doesn't improve things still i am getting DC shift in my ECG. There is any way to remove like using AC coupled input as it used for respiration input. Any help on hardware side will be appreciated.

    Regards
    Anurag Tamboli
  • 0 in reply to Anur@g Tamboli
    TI__Mastermind 38745 points
    Hey Anurag,

    Your hardware looks valid, and you are using wet electrodes, so it does not seem like this is a hardware issue. Are you able to successfully measure the internal test signal?

    Brian