Configuration for universal analog input in AD7124_8

Hi,

!)I want to use AD7124_8 for universal analog input. So that I can connect channel number RTD or TC or 4-20mA or 0-10V.Is that possible with Ad7124_8?

2) AD7124 ADC 8 channel differential input is there so that can use channel one for RTD  application, Channel two for Thermocouple application,channel three for 4-20mA application, and channel four 0-10v application. So is that possible to configure like this way in AD7124_8?

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  • 0
    •  Analog Employees 
    on Nov 19, 2020 11:44 AM 1 month ago in reply to heatcn

    Hi, 

    There's no issues with Pin12,13 or SYNC pin left unconnected. I think it is also fine to have single analog and digital plane if you are not operating in a harsh environment. But I would recommend to have at least a separate supply for AVDD and IOVDD as digital section should be a bit noisy and could affect your analog measurements. But in terms of communication point of view, I don't think it has a big impact. However, in the attached schematic I noticed that you used different symbols, can you clarify that both AGND and DGND and MCU GND at some point are externally connected?

    Another suggestion is to at least check the MCU first with a scope if it is outputting what you desired to write to the ADC before connecting it to the daughter board. This is just to know if the issue is with the code or MCU itself or when you tried to connect them with your daughter board. 

    Thanks,

    Jellenie  

  • 0
    •  Analog Employees 
    on Nov 19, 2020 11:44 AM 1 month ago in reply to heatcn

    Hi,

    Your hardware setup should not affect communication as the IOVCC is the same as VCC, probably 3.3V in your case. Probably your setup is the same as EVAL-AD7124-8-PMDZ so check out this schematic: https://wiki.analog.com/resources/eval/user-guides/circuits-from-the-lab/eval-ad7124-8-pmdz#schematic_pcb_layout_bill_of_materials


    To verify that the communication is working you can simply try to read the ID register and then check the rest of the registers. If your reading is incorrect, one reason may be the reference selection in the setup, or the reference is not enabled.

    Regards,
    Mihai 

  • Hi,

    When am comparing my hardware and EVAL-AD7124-8-PMDZ  both are almost the same. For my hardware, I added some RTD and thermocouples circuits is added apart from I think both are the same.

    For your reference am attaching my schismatics please have a check.

    Can you share with me the sample code for the reading ID register?.

    5047.SCHEMATIC1 - PAGE5.tif

  • 0
    •  Analog Employees 
    on Nov 19, 2020 12:51 PM 1 month ago in reply to heatcn

    Hi,

    From your schematic, I see that you are using for some analog signals, the digital ground, and for other the analog ground. You will need to use digital ground only for digital signals and analog ground for analog signals and then connect these two grounds together through a ferrite bead to reduce the injected noise from the digital section to the analog one.

    Or you can use a single ground.

    One of my colleagues will help you with the sample code.

    Regards,
    Mihai

  • Hi,

    Now am using single ground by shorting digital and analog ground. and made some changes in my hardware as per CN0391 hardware. Still am facing the same issue. 

    If you can share the code it will be geat helpful to me.