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Original question:

ADS1293: ADS1293EVM

ADS1293: ADS1293EVM

Arash Z
Prodigy 170 points

Part Number: ADS1293
Other Parts Discussed in Thread: , ADS1299-4, ADS1294

Hi, 

I m trying to use the ADS1293EVM board and a 5 lead ECG cable to monitor the fetal heart rate of a baby during a mother's pregnancy.

At first, I had many issues with noise, which I eventually managed to remove by shielding my ECG cable. 

 

To make sure my hardware setup works fine, I used the same setup suggested in the Data-Sheet in order to obtain the ECG signals of an adult. This worked fine and I am able to detect the correct peaks when positioning each lead on the specified position (Arm/Leg) on the body.

For the second test, I took all the 5 leads and positioned the sensors on various places on the belly of an adult person. I was once again able to obtain a similar set of results by observing the correct peaks in the ECG cable.  

In the 3rd step, I positioned the 5 leads on the belly of a pregnant woman. For a very short period of time, I was able to detect both the heart rate of the mother and the fetal heart rate in between the peaks. But this was not very strong and I have failed to replicate the same peaks ever since.

I have noticed there are many different default parameters on the software itself which I am not familiar with. Can someone please let me know if there are any settings that I can change within the software, in order to amplify the received signal, or perhaps change the filtering of the signal in order to obtain the desired signals?

Any help as to what needs/should be changed is greatly appreciated.

Many thanks

Arash  

  • 0
    TI__Guru 57662 points

    Hi Arash,

    Very interesting to hear the progress! There are a few things you can do here. 

    You can lower the reference voltage using the 8.6.6 Reference Registers bit [0]. You can power down the internal reference, then provide a lower voltage external reference to the CVREF pin. This will make the FSR of the input smaller, which means that the signal will take advantage of a larger percentage of the FSR. 

    You could implement digital filters in your control module. Unfortunately we do not have much expertise here.  

    The gain of the INA's for the ADS1293 is fixed at 3.5. You may want to consider switching to a device such as the ADS1294, ADS1299-4, etc that has programmable gain options greater than 3.5.