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EMG signals

Tomasz Sowada
Prodigy 25 points
Other Parts Discussed in Thread: ADS1298ECGFE-PDK, ADS1298, ADS1299

Hello,

I have  a ads1298ecgfe-pdk  module, can i measure EMG signal with  this? how?

Thank you for your help!

Tom

  • 0
    TI__Mastermind 46290 points

    Tomasz,

    We've seen the ADS1298 and it's related parts in use with several other biomechanical applications, including some cool stuff using the ADS1299 to detect a variety of muscle actions. EMG in particular isn't something we've tackled before though, we've focused on ECG and EEG. Can you share some more information about the magnitude of the signals to expect? What sort of probes are used?  What other care-abouts are there for EMG applications? Your best bet would probably be to find a simulator of some sort for EMG signals and then create a connector that interfaces the differential input pins for the ADS1298ECGFE-PDK, that was our approach for ECG and EEG.

  • 0 in reply to Kevin Duke
    Prodigy 25 points

    hi

    Thanks for quick answer.

    The magnitude of EMG signals is from 2 -5mV  with a frequency of 10 -500 HZ.

    I have the typical ECG electrode Ag/AgCl.

    To measure EMG signals i need signal from 2 electrodes they are located at the muscle and the differential signal from the electrodes is ma output.

    Can I do the differential signal only with the jumpers on the board or I need to do a new board?

    Sorry for my poor English.

    Tomasz


  • 0 in reply to Tomasz Sowada
    TI__Mastermind 46290 points

    Tomasz,

    All of the differential input pairs are available, so you could drive the device with either single ended or differential signals. The device can also be configured to use a bipolar supply. For more information refer to the EVM-PDK user's guide - section 5.1.

    Concerning the rest of the metrics - A 2.5V reference for the ADS1298 gives you a resolution of ~0.298023259uV, or 16777 steps of resolution across a 5mV signal (ideally, anyway - depending on the digital filter settings & characteristics some of these bits will be lost to system noise and quantization error). The ADS1298 supports a variety of data-rates, using the on-chip clock you may choose from: 250SPS, 500SPS, 1kSPS, 2kSPS, 4kSPS, 8kSPS, and 16kSPS by changing the oversampling ratio of the sinc filter. The trade-off is lower data-rates means more effective resolution while higher data rates mean less effective resolution. The most important piece is to make sure that you keep away from the attenuation regions of the sinc filter for your signals while achieve the resolution you require for your application. I suspect you'll need to stick to 4kSPS-16kSPS to try to stay in, or near, the maximally flat region of the sinc filter's frequency response. You'll have to investigate which of those filter settings gives you the effective resolution you need to reconstruct your signals as desired.

    While we haven't seen a whole lot of people attempting EMG, at least not that I'm aware of, I don't see any glaring reasons why it wouldn't work. There could be some more intricate care-about than what we've discussed here, though.

    I would recommend finding or creating a good EMG simulator as well. Connecting yourself or another person to the EVM-PDK is not what the kit was designed for - there is no protection circuitry to keep you safe from something going terribly wrong. 

  • 0 in reply to Kevin Duke
    TI__Mastermind 46290 points

    ...and I'd like to add that none of that took into account the most obvious attraction to the ADS1298 for low-level signals - the PGA! If you used the PGA you could increase the number of codes you've got to represent your 5mVPP signal.

  • 0 in reply to Kevin Duke
    Intellectual 835 points

    Hi kevin, I have a doubt. Right now i am working in EMG project using ADS1298, I'm using 1k sampling frecuenqy I want to know how the sinc filter filter the signal and what is the cutoff frequency if I use 1ksps. 

    If you have an Emg example project, I really apreciate.

    Thanks.