• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 46 subscribers
  • Views 944 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

ADS1293: 12 Leads ECG

ADS1293EVM: ADS1293EVM

Arash Z
Prodigy 170 points

Part Number: ADS1293EVM
Other Parts Discussed in Thread: ADS1293

I have been working on a project that aims to detect fetal heart rate during pregnancy. For this purpose, I have designed the setup listed below:

  • 1x ADS1293EVM board and the provided software
  • 1x 5 Lead ECG Cable with a DB9 connector
  • 5 electrodes positioned in various places of the chest and body

The reason to use the ADS1293EVM has been the ease of setup and the software that comes with the board. I have also noticed that the TI also offers an ADS1293 front end module, which I do not have any idea as to what the difference is between the 2.

Using the EVM board, I have managed to perfectly detect the heart rate of the mother, but have had very little luck with the fetal heartrate. Typically, one should be able to see a much smaller peak, in between the larger peak of the mother’s heartbeat.

1 - Does anyone have any idea as to whether this is the right setup to use or I have chosen the wrong board for such a project?

I have had the idea of linking more than 1 board together, in a master and slave setup, in order to allow for higher number of leads to be used in order to cover more positions on body. However, there are no info on such a setup anywhere on the ADS1293EVM board data sheet or the web.

The only info I have found came from the data sheet of the ADS1293 front-end module as shown in the attached picture. It shows 3 of these chips connected together, allowing for 8 to 12 leads to be attached in various configurations. I have very little info on how to connect such boards together and the data sheet is extremely unclear and I would appreciate if you could clarify the point below.

2 – What is the difference between the ADS1293 and ADS1293EVM? They are 2 different parts listed on the TI website.

3 – Based on the attached picture from the ADS1293 data sheet, can the ADS1293EVM board also be linked up as master and slave in the same manner? Or the ADS1293EVM is treated as a complete board that is final and cannot be added to other similar equipment?

4 - If so, how one can link up the necessary point and connectors between the 3 boards? I have very little knowledge on this.

5 – The example shown in the picture is for 10 leads. If I want to use the setup for either 9 or 12 lead configurations, do I just simply link up any free IN pins for that purpose?

6 – Let assume that I have managed to link up the 3 boards together. On the attached picture, the leads seem to be individually linked to the 3 boards. How one can do such a thing if you are using a lead with either a DB9 connector for 9 leads or a DB12 connector for 12 leads?

I would really appreciate any help in clarifying these points or a referral to any page that may show examples. My knowledge on such setups is not advanced enough to move forward unfortunately.

 

 

  • 0
    TI__Guru 68916 points

    Hi Arash,

    Thank you for your post. We're glad to see you're continuing to progress with your ADS1293 fetal ECG project.

    I'm not sure where your confusion is coming from between the ADS1293EVM and the ADS1293. The ADS1293 is a 3-channel, delta-sigma ADC. The EVM is an example system design which contains the ADS1293 and the supporting circuitry around it. The EVM interfaces between the ADC and the PC with the provided USB cable and software.

    Your ability to resolve the fetal ECG waveform is purely determined by your system's resolution. If the noise in the signal chain is greater than the fetal ECG, then you will not be able to resolve it. Several measures can be taken to maximize the resolution of this type of application, including minimizing electrode impedance, low-pass filtering external noise, driving the shield to reduce noise coupling, etc. It's up to you as the engineer to determine the required dynamic range needed for the application.

    The ADS1293EVM is not intended to be combined with other EVMs, which is why it is not documented in the User Guide. If you decide to modify the hardware and interface the devices with your own controller and firmware, we cannot provide any support.

    Best regards,

  • 0 in reply to Ryan Andrews
    Prodigy 170 points

    Dear Ryan, 

    Thank you for your reply. May I ask a few more questions, please... 

    So the EVM has basically provided the ADS1293 with the supporting circuitry in order for me to be able to plug into a computer without the need for any further equipment? and If so, is the 5 lead configuration I am using, my maximum allowed of number of leads with this module? 

    On the option of low pass filtering or driving the shield to reduce the noise, are these options that are already available on the provided software with the EVM board? If so, where would I be able to get info on how to change or implement them?

    Am I wrong to assume that a higher number of leads/electrodes would lead to a better signal being obtained?  

    If I do decide to move to use the ADS1293 front end module in order to combine it with a further 2 modules as given in the User Guide, what other equipment I would need to make a working prototype? 

    Kind regards

    Arash 

  • 0 in reply to Arash Z
    TI__Guru 68916 points

    Hello Arash,

    Please refer to the User Guide's complete schematic and bill of materials for details on all components included with the ADS1293EVM. The maximum number of input electrodes is 6 using pins IN1-IN6, of which you can choose any two for each ADC in the ADS1293.

    Unfortunately, I do not see filtering or shield options available on this EVM. The connector shield is shorted to ground, which is ok for testing purposes. This is preferred over leaving the cable shielding floating.

    Arash Z said:

    Am I wrong to assume that a higher number of leads/electrodes would lead to a better signal being obtained?

    Each channel is measuring between two electrodes only. Increasing the quantity of electrodes in an ECG system allows you measure additional ECG vectors, which yields more diagnostic information (assuming you have enough ADC channels). But in terms of signal quality, it doesn't make a difference. Larger electrodes with more surface area reduces the electrode impedance, which may improve signal quality.

    Your last question is beyond the scope of this forum. I've already said we cannot support this.

    Best regards,