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ADS1292R ----the channel of respiration impacts on the signal of ECG

hello

Using the ADS1292R,I find the signal wave of ECG will change to bad if   using the channel of respiration.

please help me find the source of  problem.this is my schematic design.

this is 

In addition,if I dont use the low-pass filter circuit,should there be a resistor to match the input impedance?I find the resistors(100K) can decrease the amplitude of 50Hz wave.

thank you .

9 Replies

  • Hello User,

    Thanks for your post! Can you elaborate on what you mean by the data is bad? Is the data being driven to either ground or AVDD? Is it corrupted or truncated? What is the purpose of C36 & C38? You may want to try replacing these with a 0Ohm resistor.

    Why do you not want to use a low-pass filter circuit? The input impedance of the ADS1292 is magnitudes higher than 100kOhm so while I would expect a slight decrease in magnitude over the resistor I do not think it will be significant.

    Best regards,

    Alex Smith
    Applications Engineer | Precision Delta-Sigma Converters

    Check out our helpful resources:
    TI Precision Data Converters | TI Precision Labs - ADCs | Analog Engineer's Calculator Data Converters Learning Center | Selection Guide

  • Hello,

    Thank you for your post.

    Are you saying that the ECG data on Channel 2 looks worse when the respiration feature on Channel 1 is enabled? Can you please share an example of the results and the register settings for each test?

    Best Regards,

    Ryan Andrews

    Precision ΔΣ ADCs

  • In reply to Alexander Smith:

    Hello

    Thank you for your reply.

    My schematic diagram is designed according to the TI's example(tidrk32)

    C36 and C38 of my design corresponds to C56 and C63 of TI's example. it is used for high-pass filter.I may try to replace 0R resistor.

    best wishes!

  • In reply to Ryan Andrews:

    Hello Andrews

    Thank you for your reply.

    Yes,What you said is what I want to express.

    I didnt save the result wave diagram.I cant distinguish the ECG wave if I weld the respiration module circuit ,It is random wave.this is my register settings

    .

    Best wishes.

  • In reply to user4365468:

    Apologies, I believe that is a patient protect capacitor. I didn't recognize it initially. We'll take a look at your registers and let you know what we see.

    Best regards,

    Alex Smith
    Applications Engineer | Precision Delta-Sigma Converters

    Check out our helpful resources:
    TI Precision Data Converters | TI Precision Labs - ADCs | Analog Engineer's Calculator Data Converters Learning Center | Selection Guide

  • In reply to Alexander Smith:

    Hello - We will review the registers. Please share an example of the data on Channel 2 that you collect with Channel 1 enabled and disabled for comparison. Remember to also specify the input signal amplitude and frequency.

    Best Regards,

    Ryan Andrews

    Precision ΔΣ ADCs

  • In reply to Ryan Andrews:

    Hello

    Thank you!

    I weld  a new PCB,this is my sample diagram.

    1、No respiration channel(no C36&C38):


    2、have C36&C38

    this is my digital-filter arithmatic

    (effect is not good)

    By comparison,It is better than the old pcb.I should make more digital filter and it will be good. I didn't recognize the ECG wave of  the sampling wave diagram of old PCB in the past .

    this is raw datas:

    ECG(no respiration).txt

    ECG(respiration).txt

    sample rate:250sps

    amplitude:raw data*200(V)

    It is strange that the 24bit sample value is 7FFFFF of respiration channel??

    Thank you for your reply.

    It should be good,I will try other digital-filter.

    Thank you!

    Best wishes.

  • In reply to user4365468:

    Hello,

    I'm happy to see that things are improving!

    When you say "have C36&C38" do you mean that they have been uninstalled or that the resp channels are dissabled?

    I noticed that in your RLD_SENS register that you have RLD lead-off sense enabled. Try disabling this. 20H instead of 30H.

    Best regards,

    Alex Smith
    Applications Engineer | Precision Delta-Sigma Converters

    Check out our helpful resources:
    TI Precision Data Converters | TI Precision Labs - ADCs | Analog Engineer's Calculator Data Converters Learning Center | Selection Guide

  • In reply to Alexander Smith:

    Hello
    Have C36&C38 only means that they have been uninstalled (respiration channel always been enabled).
    ok,I will follow your advice to do.
    Thanks for your reply very much.
    Best wishes!

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