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ADS1291 AND STRANGE READINGS

HECTOR
Intellectual 865 points
Other Parts Discussed in Thread: ADS1293

Hi

I am using Fluke to test my product , I noticed that when I use FLUKE with battery no power (220VAC -50Hz) I get very nice signal. but when I power FLUKE the ecg signal is distroyed , I tested other ECG instrument that was able to read ECG from FLUKE with AC powered, so I agree that the problem is my circuit.

All my readings include

baseline filter IIR

lowpass filter FIR

50Hz Nortch filer.

but I could not solve the problem .. the problem might be because I dont use RLD ..I really confused here .

 

 

Any Idea to solve this problem please ?

What am I missing here ?

Regards

Hector  

 

  • 0
    TI__Mastermind 43915 points

    Hi Hector,

    Again, sorry for the delay as I have been on vacation.

    If the problems you are having only occur when you plug the simulator into the wall, that tells me it may be something coming in from the outside. The 50Hz is filtered out from your notch filter but the harmonics from the 50Hz are going to couple right through. See if you can decrease your LPF down to 40-50Hz for testing to see if it is those higher components coupling through.

    You do not have to use the RLD as long as the inputs are biased properly using high impedance resistors. I would have to look back through your posts to see your front end design again. Or could you repost it so I can make sure it is correct?

    Regards,

    Tony Calabria 

  • 0 in reply to Tony Calabria
    Intellectual 865 points

    Hi Tony

    Thank you again

    When I use a LPF with 40-50hz I cant read ECG data with 110bpm and more .

    Here is the shematic , also please check my Pace detection because itis not working well too .

    Regards

    Hector

     

  • 0 in reply to HECTOR
    TI__Mastermind 43915 points

    Hi Hector,

    You should still be able to read back ECG at 110bpm with a 40Hz cut off frequency. What do you see in terms of the output data when you change your filter to 40Hz?

    The PACE detection circuit I would need to see scope pictures at the points similar to the ppt I have posted. Its hard for me to debug without getting an idea of what type of signal is showing up at certain points. Can you take scope pictures at the points I have shown in my ppt to make a comparison of how this circuit is differing from my test circuit. Keep in mind that the test circuit I put online is a starting point and has only been tested with a simulator. I do not know how it will behave with a patient.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Intellectual 865 points

    Thank you  Tony ;

    After  a long digging over the problem ; I found that the problem the main supplly ; and from lead detect; after i turned lead detect off the readiing become great and 40Hz lowpass filter works now. but I still need lead detect I am using internal current ; I think I cant use external pullup due to my configurations of one lead reading , is that right ? or any suggestion in this ?

    We are planning to move to ads1293 seems more flex and better but we still need time to move .

    Regards

    Hector

  • 0 in reply to HECTOR
    Intellectual 865 points

    How can I make lead detect work using external  resistors ; knowing that I am using pullup from RLD?