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ADS1292R: Pre-amplifier stage for EMG readings

Part Number: ADS1292R
Other Parts Discussed in Thread: ADS1292, INA118, LP5907

Hi,

I am using an ADS1292R for reading EMG signals with 3 Electrodes, I made a PCB which connects to a microcontroller (Teensy), the system is battery powered.

I have used a signal generator to inject signals from 10uV to 10 mV to the ADS1292 and also connected the electrodes to a muscle. First, I have observed that a gain of 12 is not enough, part of the signal is in the noise level. Second, When I use the electrodes on me I notice the signals has an offset even though I use the OFFSETCAL command.

So here are my questions:

1. Could you guys advice on how to do a pre-amplication stage?

2. Is the INA118 a good option ?

3. What about the RLD signal? How do I route it to the INAMP?


Here is the Schematic of the sensor board:

Best Regards.

Carlos

  • Hi Carlos!

    Did you look at those other posts I referred you to regarding the ADS1292 for EMG applications?  I have no issues with you using the INA118 as a pre-amp.  The RLD would provide a common mode based on your LP5907 voltage (AVDD/2), you should not have to run that through the INA, but you may want to use it as a reference to it.  What sort of offset voltage do you see with the circuit 'as is'?

  • Hi Tom!

    Yes I have seen a few, but I didn't understand entirely. I am having reading of maximum ~2mV, here is a graph of a signal reading from my biceps and its FFT: :

    In that capture I tried to contract my muscle 4 times, each time stronger than the previous.
    Previous graph doesn't show the offset because I applied a Bandpass filter which corrected it.

    The following graph is the Raw signal, you can see an offset of about 16mV