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ADS1293: 3 ECG Channels with three electrodes schematic

Part Number: ADS1293

Hello! I need to implement a 3 channel ECG meter that uses 3 electrodes. Is it possible to do this with ADS1293? I tested the circuit with 4 electrodes, on ADS1293EVM, and it works good! But when I disconnect RL electrod ECG is very noisy. I also don`t find any information about 3 electrodes schematic in datasheet.

Also I'm found some links and test this solution (When RLDOUT connect to all channels through resistors 10M), but it doesnt work to.

ADS1292R starting questions - Data converters forum - Data converters - TI E2E support forums

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Other Parts Discussed in Thread: ADS1292R , ADS1292 , ADS1292ECG-FE Hello All ; I am happy to join TI forum ; I am digital engineer I have good analog background

ADS1293: Can I use the ADS1293 for a 3 channel EMG - Data converters forum - Data converters - TI E2E...

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Part Number: ADS1293 Electromyography (EMG) is the standard modality for measuring muscle activity. I need to record 3 different muscles. These muscles are

  • Hello Maksim,

    Welcome to our forum and thank you for your post.

    It sounds like you are using the three primary electrodes (RA, LA, and LL) for ECG measurement with a fourth electrode (RLD) for biasing the body. The quick answer to your question is that, by removing RLD, your input signals do not have a defined common-mode voltage.

    Remember that the body's electrical signals are floating with respect to the ECG measurement system. Without establishing the common-mode voltage, the input signals can exist outside the usable range of the amplifiers inside the ADS1293. This can give poor results. Also, the RLD helps to reject the common-mode noise (i.e. power line noise) on the electrode inputs. Without RLD, you will need to AC-couple the electrode inputs.

    Please review some of our overview material on ECG applications contained in this video training series:

    https://training.ti.com/how-measure-ecg-guide-signals-system-blocks-and-solutions

    Best Regards,

  • Hello Ryan,

    I watched these videos, but did not find the answer to my question. Maybe there is a ready-made schematic solution that I could check.

  • Hello,

    Maksim means how to use ADS1293 without RLD electrode. There are some suggestions in the Internet for another chips. Is there right solution for ADS1293: 3-channels ECG measurement using only RA, LA, and LL electrodes?

    BR
  • Hello Maxim and Maksim,

    You may use any of our ADS129x devices without the RLD electrode. The only change needed is the inputs must be AC-coupled instead of DC-coupled.

    One way to do this is to use a resistor divider after the DC blocking capacitor in series with each electrode:

    Another way is to use a single pull-up resistor to the output of the RLD amplifier:

    Best Regards,