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EMG data read and normalization

Hi,

i'm developing a emg system data acquire and processing.

I've already save 3 samples of EMG signal.

Now i'm trying to read these files, get their max values, divide by 3 (number of signals) and set this "reference value" as 100% in a vertical container bar (normalization).

A new data acquisition now is done in real time, and I'd like that in the container bar shows which % (atual signal / "reference value") are being applied.

I'm afraid that I'm not doing right the normalization.

Could someone help me, please?

Thank's a lot.

It's attached the VI and 3 signal samples.

Message 1 of 5
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Hi Ramon,

I think your codes could work as you decribe here. Do you run into some issues? The only note I would add is - from your DAQ Assistant,  you will read 200 points one time, however, you wire  to a scalar. It will only display the last element of the 200 points.

Thanks!

ZJ Gu

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Message 2 of 5
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hi, im working in emg adquisition too, but i wanna ask you what is the voltage range of a emg signal, some papers says that emg signals are in micro volts range and others says this signals are in mili volts range, so, i dont know what to use, the ni usb 6009(milivolts range) or ni pci 6221 (micro volts range) and i dont know if i should pre-process the signal before the adquisition card.

im doing an up limb adquisition using two adquisition chanels in the arm

thanks x help

.:. Pedro Rivera .:.
i love to work and develop on labview, this is real fun!!!
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Message 3 of 5
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Hi Pedrorivera

The EMG signal is in the range of 50uV to over a 1mV.  You will definitely need an amplifier because the signal that you are acquiring is coming from a high-impedance source (surface electrodes with typical 10Kohms impedance) and you need a differential amplifier with very good common-mode rejection to attenuate the common-mode noise that you will pick up on the subject to a variety of both physiological and non-physiological sources.  You also need some measure of safety to prevent possible shock hazards.  See this posting for more info:  https://decibel.ni.com/content/docs/DOC-4670

Steve

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Message 4 of 5
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Hello pedrorivera,

as Steve.J already said, you should use some amplificator before get the analog/digital signal.

I'm using actives differential eletrodes (they are 20x amplification), and a signal conditioner from "EMGSystem do Brasil", which do a passband filter, to elimine noises, and amplify it in 100x.

The signal amplified (yet analog) by the signal signal conditioner goes into USB-6218 from NI. This equipament is a A/D, and have a max output of 3V.

Ramon Campos

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Message 5 of 5
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