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ADS1292: Lead-off detection is unstable especially when RD was off

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Prodigy 10 points
Part Number: ADS1292

My project need to measure two channels ECG signal and using ads1292. There are 4 leads, such as IN1P , IN2P, RD and COM,  which COM is a common electrode with connecting  IN1N and IN2N  together. I select DC lead-off detection method. When the RD is on, it is usually normal. But when the RD is off, the LOFF state of the other leads sometimes are unstable like a trapezoid wave with 50Hz frequency no matter that lead is off or on. So i think the lead detection is disturbed by power frequency. And i choose various LOFF current magnitudes and comparator thresholds with LOFF register to avoid this problem, but it doesnot work.

How can i fix it. Thanks.

figure1:schematic diagram

figure2:LOFF state output with 50Hz

  • 0
    TI__Mastermind 19815 points

    Hi,

    May I ask do you happen to have/use ADS1292 Evaluation kit/board(EVM) and ECG simulator?

    Have you tried your experiment with the ADS1292 Evaluation kit/board(EVM) and ECG simulator and note down the registers settings/configurations?

    Could you clarify what do you mean by "RD"?

    Do you use PACE detection? It's suggested to turn off PACE detection function first during the the development and trials phases.

    Do you use DC resistor method or DC Current method for Lead Off detection? Is your power clean?

    Are you trying your experiment using an ECG simulator?

    What was the signal in Figure 2 you showed above?

    Can you show a waveform comparison between Lead-On and Lead-Off?

    Can you try different settings for COMP_TH2 COMP_TH1 COMP_TH0?

     

    Do you use RLD? RLD has certain effects to the Lead-Off detection sensitivity. Theoretically, using RLD helps suppress the common mode noises/interferences and improve the Lead-Off detection. 

    Also, How did you power up your ECG system and the computer/laptop that are used to communicate with the system?  Can you try use a laptop without connecting to the wall outlet?

    Thanks,

  • 0 in reply to ChienChun Yang
    TI__Mastermind 19815 points

    Hi,
    Since I did not hear back from you, I believe my suggestions answered your questions.
    I will close this post and if you have any pending questions, feel free to post them here or open a new thread.
    Thanks and have a great day!