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Acquisition of 3 Channel ECG data from ADS1292R

Santhana Kumar
Prodigy 150 points
Other Parts Discussed in Thread: ADS1292R, ADS1291, ADS1294

Hi All,

We are currently using ADS1292r for acquiring single lead ECG (LA-RA) and respiration signal, similar to the TI evaluation board. Now, our requirement is to acquire three lead ECG data namely (LA-RA), (LA-LL) and (RA-LL) from the same ADS1292r. As per the datasheet explanation at page 19, if respiration feature is not used in AFE, these channels can be used as ECG inputs.

There are only 2 ADCs and the ADC gives out only 2 channel data for a single conversion. If 1st and 2nd input channels are connected to the ADCs, we need to change the multiplexer before acquiring the third channel.  If the ECG signal has to be acquired at 500Hz, is it possible to have all the 3 lead information at 500Hz?Please confirm.

Thanks,

Santhana Kumar

  • 0
    TI__Mastermind 18275 points
    Santhana,

    I am moving your post to the Precision Data Converter forum. They will be better equipped to answer your questions on this device.
  • 0
    TI__Mastermind 38745 points
    Hey Sanantha,

    I'm not aware of any way to multiplex a third channel on to the ADS1292R. Have you considered using an ADS1291 daisy-chained to the first device? It is possible to synchronize conversions between devices to gather three channels worth of data. Alternatively, have you considered the ADS1294? That device features 4 conversion channels.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    TI__Mastermind 38745 points
    Hey Sanantha,

    I'd like to clarify; it is possible to use the RESP_MOD pins to measure a third lead, but there are a few issues with that. Such a measurement cannot be done synchronously with the other two. You'd have to take data for two channels, mux in the third, wait for that data to be ready, collect that sample, then mux back. In addition, the digital filter on this device takes three conversion cycles to settle, so the data you collect when you switch to the third lead would not be settled. Alternatively, you could speed up the data rate and simulate a 500 SPS data rate, but the digital filter has a wider band response at higher data rates (i.e. more noise), so I do not see that option as being attractive.

    If using a daisy-chained ADS1291 or the ADS1294 are not options for you, it is possible to calculate the Lead III voltage from the other two in real time since the leads represent a triangle formed by three vectors.

    Regards,
    Brian Pisani