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Human heartbeat example for 4444 ?

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Human heartbeat example for 4444 ?

Postby nurber » Sat Oct 14, 2017 4:56 pm

Hi Forum. I'm trying to get similar results to those shown at https://www.picotech.com/library/oscilloscopes/rejecting-common-mode-noise-in-oscilloscope-measurements. Using 441 with red lead in hand and black in the other the best I can do is attached which has 13Hz lowpass filter in addition to 200kHz bandwidth limiter. Any higher lowpass including the 20Hz cited in above link results in waveform with 60Hz noise. Can somebody steer me in right direction or perhaps upload a known working .psdata for capturing this waveform? Thanks.
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Re: Human heartbeat example for 4444 ?

Postby alan » Mon Oct 16, 2017 10:27 am

Hi,

The human heartbeat is a small signal to pickup in a noisy environment. Can I suggest you try to make sure there are no mains cables near your body, try running the laptop of batteries and perhaps switch off any lights near you.

Proper medical ECG machines tend to use 3 electrodes - one of which feeds an inverted version of the noise back into the body, often using an electrode connected to the leg. We dont have this when just using a scope so have to be a bit more careful.

Please when you have tried this also upload the .psdata file.

Thx
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Re: Human heartbeat example for 4444 ?

Postby Gerry » Mon Oct 16, 2017 10:31 am

Hi nurber,

It can be tricky to recreate but I found that in a reasonably clean environment (as mentioned by Alan) if you follow the example but use 10Hz instead of 20Hz, and also use a 10s total capture time (1s/div), you should be able to create the waveform.

The psdata file is here:

Heart-beat trace.psdata
(1.26 MiB) Downloaded 5 times


Regards,

Gerry
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