AD4110-1 noise issue with Thermocouple

Hello,

I am interfacing Thermocouple K type with AD4110-1 ADC.

I got difference of 4 to 5 degree Celsius.

example: I set a temperature of 50 degree from calibrator, I got an output from ADC is 46 to 49 degree Celsius.

How to reduce noise?

is there any register configuration required?

Also I have attached register configuration data of my AD4110-1.

Thanks,

Jaydip

  • 0
    •  Analog Employees 
    on Apr 6, 2021 12:36 PM

    Hi, 

    I'll be moving this thread to Q&A - Precision ADCs - EngineerZone (analog.com)

    Someone here can better assist you. 

    Thanks,

    Jellenie

  • 0
    •  Analog Employees 
    •  Super User 
    on Apr 7, 2021 2:09 AM

    Hi Jaydip,

    May I know if what Cold Junction Compensating(CJC) did you used for this Thermocouple measurement? I noticed in the register settings that you only enabled one channel. When measuring a Thermocouple, another channel for the CJC is required. If you can share your schematic and test setup, then that would be helpful. I will also contact the product owner to further support you.

    Regards,

    Andrei

  • Hi Andrei,

    I used LM35 temperature sensor for cold junction compensating(CJC).

    I enabled both channel simultaneously for cold junction and thermocouple hot. so in register settings you seen only one channel enabled.

    Enabling enhanced 50 Hz/60 Hz filter works for RTD noise cancellation but not working for Thermocouple interfacing.

    Another question: Is it possible to read both channel at a time if  both channel enabled together?

    Thanks,

    Jaydip

  • 0
    •  Analog Employees 
    •  Super User 
    on Apr 7, 2021 5:41 AM in reply to jd_fev

    Hi Jaydip,

    Okay, thanks for confirming. For your question, it is not possible to read both channels at a time but this ADC can enable more than one channel and sequentially reads through each channel. When all the channels complete the conversion, the sequence starts again from the lowest enable channel to the highest enabled channel. Then the data register is updated as soon as each conversion is available. It is better to enable both the TC channel and the LV inputs for your CJC rather than enabling/disabling it one channel at a time. 

    Once you've done the above settings.

    Can you share the following measurements/info below:

    - Measurement for each channel?

    - Measurement from TC and CJC?

    - Are you seeing the same variation in your CJC?

    - The data log of the actual measurement like code or in voltage or in degC. (sampled at least 100 or 1000)

    - Is it possible to share your actual setup? to see the placement of CJC and wirings. 

    Regards,

    Andrei

     

  • Hi Andrei,

    I have done the settings as suggested by you.

    but readings are not sequentially, some time getting continuous readings of same channel.

    Following's are the Raw output code of each channels:

    Sr no. CH0 readings(TC) at 0' Celsius CH1 readings CJC
    1 32522 36659
    2 32535 36659
    3 32533 36663
    4 32539 36664
    5 32534 36664
    6 32541 36659
    7 32546 36663
    8 32549 36671
    9 32553 36668
    10 32550 36671
    11 32545 36677
    12 32538 36685
    13 32550 36685
    14 32545 36684
    15 32541 36690
    16 32537 36689
    17 32540 36690
    18 32548 36691
    19 32518 36690
    20 32540 36689

    Thanks,

    Jaydip