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ADS1293

Andres Pineda78
Prodigy 10 points
Other Parts Discussed in Thread: ADS1293EVM, ADS1293

Hi,

I have an ADS1293EVM board and have successfully used it with gel-type electrodes to get 3-lead ECG readings. I am experimenting with the use of dry-contact sensors to develop a wearable ECG sensor. Specifically, I am attaching PS25251 EPIC Ultra High Impedance ECG Sensor and connecting them via two 3.7V batteries to get the dual polarity ( +- 3.7V). Here is the datasheet of the sensor:

Link

Connections from the EPIC sensors via shielded cable are as follows:

VDD to +3.7V battery

VSS to -3.7V battery

GND to Board GND

Signal to IN1A 

I am getting a lot of noisy spikes on the ADS1293 signal trace and cannot seem to tune the ADS1293 to accept the new sensors. When I go back to the gel-electrodes, the ADS1293 works fine.

Can you recommend what parameters (registers) need to be changed to make these electrodes work with the ADS1293?

  • 0
    TI__Expert 3350 points
    PS25251 is an active dry electrode sensor not suitable for use with ADS1293 because the amplifier on this sensor would affect the functionality of the ADS1293 circuits.

    The ADS1293's RLD circuits provide a low impedance path from the patient body to the ADS1293 circuit, establishing a needed ground reference for ADS1293. The amplifier in PS25251 not only interferes with this functionality, but also it would affect the functionality of the Lead-off detection. This feature works based on the principal of injectioning a small amount of current into the patient to determine if the path is open or not. the current needs the RLD path to return to the ECG ground plain. In this case the current would be injected to the output of the amplifier in PS25251 instead, and hence, the feature will not function properly.
    I do not see any noise spec in the sensor datasheet and suspect that some of the noise you are observing is from the active part of the sensor.

    Regards,

    Bahram