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Author Topic: [resolved] Persistent noise with EKG-EMG shield.  (Read 3052 times)

Italque

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[resolved] Persistent noise with EKG-EMG shield.
« on: April 27, 2016, 07:04:28 PM »
Hi! I bought an EKG-EMG Arduino shield. I follow all the instructions in the user manual when I start the ecg in the electricguru I have as a result only noise. The noise go away when I disconnect the ecg cable from the shield. I follow many other advices ( for example I use only the battery of my laptop to avoid interferences) but the result is the same .Could be the cable bad shielded? Every help is appreciated!
« Last Edit: May 02, 2016, 09:49:47 PM by Italque »

LubOlimex

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Re: Persistent noise with EKG-EMG shield.
« Reply #1 on: April 28, 2016, 12:00:33 PM »
Hey,

Please hold the DRL firmly in hand. Try another channel for the data (set the jumper to another ADC).

Other than that take a look at some of the most interesting projects with SHIELD-EKG-EMG that I’ve stumbled so far:

-SHIELD-EKG-EMG controlling myo-electric prosthesis: https://www.youtube.com/watch?v=38SnocWQFkM
-Portable ECG monitor: https://www.youtube.com/watch?v=15D6zbXlQ4c
-SHIELD-EKG-EMG with Google Nexus 4: https://www.youtube.com/watch?v=h7nysCmyWiU
-Playing tetris and other games with SHIELD-EKG-EMG: https://www.youtube.com/watch?v=u8pwmzUVx48
-Helicopter controlled with muscle signals: http://www.ki-i.at/helicopter/

What kind of noise? If it is 50-60Hz noise you might need to consider software filtering. P

Best regards,
Lub/OLIMEX
Technical support and documentation manager at Olimex

Italque

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Re: Persistent noise with EKG-EMG shield.
« Reply #2 on: April 28, 2016, 10:50:36 PM »
Thank you for the help LubOlimex and for the links, the projects are very interesting(first of all the first link, because I'm a physical terapist).
I want to show you the change of the waveform before and after the change of channel.

below electrode cable disconnected from the shield
http://i.imgur.com/FJIfQYR.jpg?1

electrode cable connected (with DLR firmly connected to right leg at the medial malleolus)
http://i.imgur.com/Mk32pD0.jpg?1
(50-60 hz noise or not?)

After your wise advice (I changed the channel and I firmly held DLR in my hand)
 http://i.imgur.com/hjiu704.jpg?1



In the last image It seems to be a "flat" ecg waveform.
What do you think can be done to improve the quality ? I need a signal as much as good possible.



Thanks again,

Italque


« Last Edit: April 28, 2016, 10:52:30 PM by Italque »

LubOlimex

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Re: Persistent noise with EKG-EMG shield.
« Reply #3 on: April 29, 2016, 10:57:37 AM »
Hey,

The first picture is good result - it should be e flat line without the electrode.

The second picture is not very good result and the problem is quite likely a bad contact between the DRL electrode and the skin - try to use a rubber band or something to keep it tightly in place. Depending on the skin type you might need to use conductive gel (if your skin is dry it would be less conductive, for example).

The third picture is ok. As you see in pictures 2 and 3 the noise is consistent (there is a re-occurring pattern) so you can set a software filter which would make the lines appear smoother. However, I don't understand what you measure in pictures two and three - are you trying to read ECG? If that is the case I would suggest that you rotate the trimmer to get more amplification. The ECG waves seem very tiny. You should get clear ECG waves as seen on page 13 of the user's manual.

Best regards,
Lub/OLIMEX

Technical support and documentation manager at Olimex

Italque

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Re: Persistent noise with EKG-EMG shield.
« Reply #4 on: May 02, 2016, 09:27:53 PM »
Hi,


Yes I want to read ECG. I followed  your instructions and all the problems are solved. The discussion can be considered resolved.
I'll create another post soon on how to do an emg with the shield, your intervention will be crucial.

Thanks again LubOlimex
« Last Edit: May 02, 2016, 09:49:29 PM by Italque »