09-16-2011 08:30 AM
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.
09-21-2011 12:15 AM
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
09-22-2011 11:55 AM
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
09-22-2011 02:53 PM
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
09-22-2011 03:42 PM
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