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ads1293 output

user4366959
Prodigy 50 points
Other Parts Discussed in Thread: ADS1293

Dear Sirs,

I checked ads1293 evaluation board with function generator. Input voltage is 400mV p-p sign wave, differential + is connected to IN1 and - signal is connected to IN2. But, I observed output like 1mV p-p. Could you advice me if I have to set any other registers? I use TI's software tool for ads1293 evaluation board. 

Best Regards,

  • 0
    TI__Expert 3350 points

    The ADS1293 INAs provide a gain of 3.5x  and you should be getting 1.4 V at the output.  Check if you  are converting the ADCout, the digital output value,  correctly back to analog  value ( see  page 36 of ADS1293 datasheet). Also, make sure  the RLD signal ( a third wire)  is connected to the function generator reference ground to create a ground reference between the ADS1293 EVM board and the function generator. Finally  set the channel parameters (R2, and R3) properly to select the appropriate channel bandwidth, based on the frequency of the signal from the function generator. In general, I suggest that you use an ECG emulator box for testing, you can find very low cost version from various manufacturers in Asia.

  • 0 in reply to Bahram Mirshab
    Prodigy 50 points
    Hi Bahram-san,
    Thank you for your prompt advice. After I added signals with appropriate bias based on the datasgheet P36, I succeeded to get correct ADC output.
    Thanks again,
  • 0 in reply to user4366959
    Expert 1245 points

    Hi,

    I did not understand how to connect function generator output to the input  channels of the ads1293? can anyone please help?

    I have tested the ads1293 circuit by connecting input electrodes it to the body but i didn't got the proper output,so i need to check it using function generator.

  • 0 in reply to Parth Dholakiya
    TI__Genius 16890 points
    Hello,

    You should be able to connect a function generator directly to the inputs. You need to make sure that your signal at the pins of the ADS1293 are less than the maximum allowed signal and with the CMVR. This is explained in section 8.3.5 of the datasheet. Also, make sure the RLD signal ( a third wire) is connected to the function generator reference ground to create a ground reference between the ADS1293 EVM board and the function generator.
    Mike
  • 0 in reply to Michael Stout
    Expert 1245 points
    Hi ,
    i have following queries:
    1)I need to know do i need to connect RLDIN pin to the RLDREF pin as shown in the application circuit given in the datasheet or it need to be left floating?
    2)what do you mean by RLD signal? Is it a output of the RLD amplifier?
    please note: I have connected output of the RLD amplifier to the IN4 internally.
  • 0 in reply to Parth Dholakiya
    TI__Genius 16890 points
    Hello,

    Yes, you should connect the RLDIN pin to the RLDREF pin if you wish to control the common-mode level of the patient and improve the AC CMRR and the overall ECG system.
    RLD stands for Right Leg Drive. It is a signal to counter any differences between the reference voltage and the detected common-mode level.
    See section 8.3.12 in the datasheet.

    Mike
  • 0 in reply to Parth Dholakiya
    Expert 1245 points

    Hi,

    I am using "Heart rate" project for ADS1293 provided by ti,I have done some modifications in the code that is ODR=160hz and pin configuration as in our board we are using different pins for spi communication,Interfacing circuitry is same as given in the evaluation module for ads1293. When i collected the notifications on the BTool ,The Error packet is as given below,

    FF FF FF 00 00 20 20 00 00 00 FF FF FF FF FF FF FF FF    

    I don't understand why these two errors occurred,

    1) Positive output of INA smaller than negative output 2) Positive output of INA smaller than negative output

    I have attached the electrode same as image shown for 5 Lead application  given in the datasheet.

    also please see the attached graph which i got from the samples received,I have plotted graph in the excel sheet.

    I don't know what to do? I had put a lot time behind this but no output. please help.

  • 0 in reply to Parth Dholakiya
    TI__Guru 71516 points

    Vidula,

      Did you ever get this resolved?  If so, what was the solution?  What is the status of the design?  

    ~Leonard