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XTR110: XTR110

Hannaneh Mahdavi
Prodigy 20 points
Part Number: XTR110
Other Parts Discussed in Thread: AFE4900, ADS1294R, ADS1298

Hello,

I'm measuring ECG signals. Is it possible to use loop-powered ICs (4-20mA transmitter) with the aim of lowering ECG output noise? Is it safe for body as its current is much higher than what a body can tolerate?

Thanks

  • 0
    TI__Guru 50796 points

    Hi Hannaneh,

    ECG signals are relatively small amplitude, from 10µV to 5mV and relatively low frequency range, from 0.05Hz to around ~40-Hz. The LA and RA ECG probes are typically interfaced through a very low noise (low frequency1/f noise) instrumentation amplifier to gain up the ECG signal prior being  processed or converted into the digital domain with an ADC.  The electrodes exhibit in many cases a high-impedance output, hence, a very high-impedance differential input instrumentation amplifier front-end is required, where the probes are placed in relatively close proximity to the instrumentation amplifier stage. 

    To reduce noise, the key is to use a very low-noise instrumentation amplifier front-end to gain up the signal, combined with input low-pass R-C filters to reduce EMI and high frequency noise on the analog domain. Digital filters and DSP is very often used as well in combination to the external analog filters.  We offer integrated Delta-sigma ADC solutions incorporating the complete amplifier front-end in a single device specific for biopotential measurements and ECG applications.

    The following resources may help provide information about ECG front-ends:

    https://www.ti.com/solution/electrocardiogram-ecg

    https://www.ti.com/video/6269767539001

    Below is an example of a ECG front end using discrete op-amps and a SAR ADC discrete solution:
    https://www.ti.com/lit/ug/slau516/slau516.pdf

    The XTR110 is a three-wire current transmitter.  This device fits a different type of industrial application, accepting a single-ended voltage signal, converting the voltage into current, and transmitting the current signal over a very long distance, for industrial applications.  The 4-20mA transmitter is intended to transmit data over very long distances between control centers and sensors or actuators. This works because Kirchhoff’s laws state that current is constant at any point in a closed loop.  The XTR110 current-transmitter device only offers a single-ended input, and it is not particularly low noise, nor a high-impedance input device so it would not interface directly with your ECG probes, nor will be a device that will help reducing noise. 

    You can learn about the 4-20mA applications on the link below:

    [FAQ] Designing with 4-20mA current loop transmitters (XTRs): FAQ links

    Thank you,

    Luis 

      

  • 0 in reply to Luis Chioye
    Prodigy 20 points

    Hi Luis,


    Thank you for taking your time and answering my question. The references you provided gave me a lot of information. I read many FAQs and I have some other questions:
    1- Is it possible to design a circuit with other TI ICs to provide a circuit that transmits current instead of voltage, but a low level of current to be safe for the human body in ECG measurements? As noise can not affect the current transfer.
    2- What is the best IC or solution for measuring signals? ADS129xR or AFE4900, etc? Then how can I provide wireless communication for that with a battery?
    3- If I want to use ADS1294R, is there any evaluation kit for that? and what protection circuitry is needed that we can't use such evaluation kits for humans at all? Do I need to design my own circuit?
    4- I found many people had problems with movement noise while measuring ECG signals because movement will add additional muscle and skeletal signals to the ECG reading. If so, how ECG is measured in hospitals while running?
    5- The last question is that can I use the ADS1294R board next to the patient by reducing electrode cable size (for reducing noise)?

    Thank you so much,

    Hannaneh

  • 0 in reply to Hannaneh Mahdavi
    TI__Guru 50796 points

    HI Hannaneh,

    Hannaneh Mahdavi said:
    1- Is it possible to design a circuit with other TI ICs to provide a circuit that transmits current instead of voltage, but a low level of current to be safe for the human body in ECG measurements? As noise can not affect the current transfer

    I am not aware of an TI IC that transmits current specific to human body ECG measurements.

    There are evaluation boards for example for the ADS1298,and AFE4900 readily available on TI.com:

    https://www.ti.com/tool/ADS1298ECGFE-PDK

    https://www.ti.com/tool/AFE4403EVM

    If you have questions about the ADS1294R, and AFE4900, please submit a new query on the Data Converter forum.

    https://e2e.ti.com/support/data-converters-group/

    Thank you and Regards,

    Luis