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CCS/ADS1242: ADS1242 (ADC) datalog reader doesn't accurate and roughly value

KITTIPAT NARIPANTAWAT
Prodigy 20 points
Part Number: ADS1242
Other Parts Discussed in Thread: ADS1220, ADS1248

Tool/software: Code Composer Studio

Need support for

-Hardware reference design schematic.

-Software code for average value Analog to Digital (ADC)  ADS1242

Thanks for support.

Kittipat

  • 0
    TI__Guru* 92715 points
    Kittipat,


    Are you having a problem with an existing design? If you are, can you please describe your system and the errors that you have?


    Joseph Wu
  • 0
    Prodigy 20 points

    Dear Joseph,

    This is my customer problem.

    ADC has a problem the readed value was very rough and unstable value

    ADS1242IPWT

    Any recommend for hardware or software design. pls. let me know.

    Thank you& Best Regards,

  • 0 in reply to KITTIPAT NARIPANTAWAT
    TI__Guru* 92715 points

    Kittipat,


    The ADS1242 is an older design and we don't have any example software or designs for this device. Additionally, we would need information about what it is your customer is working on to help with an example design. A schematic would help us understand what the system is and what potential problems might be.

    Also, I'd like to see any data that the customer has generated. I would need to know the reference voltage, the input voltage, and the ADC data (in hex or decimal, not the converted voltage data). This may help identify the type of noise that you are seeing.

    However, If your customer has an unstable or noisy read, then there are a few things that they can consider. This may lead them to clean up problems in the circuit.

    1. The reference is noisy and they should use a less noisy reference - The ADC compares the input voltage against a reference voltage. If the reference voltage is noisy, then the ADC reading reflects the same noise. Using a low noise reference or a ratiometric measurement can help with the noise performance.

    2. There is EMI is coupling into the circuit - Often, some sort of electromagnetic interference will cause additional noise in the ADC measurement. As an example, if the input or reference is connected with long wires, Line noise (either 50Hz or 60Hz depending on where in the world you are) may be coupled into the system. This problem is often reduced based on the data rate used and the digital filtering of the ADC. Also, motors and other inductive elements may throw off EMI. This effect can be reduced by a conductive enclosure.

    3. A noisy supply may be causing noisy ADC readings - Most of the time the supply noise is rejected from either the power supply (PSRR) or from inputs if the signal is common-mode (CMRR). If you look at the schematic, you may find places where the supply noise comes in and is not common-mode. I would look at front end or reference conditioning, like filters or buffers.

    4. Input filtering can be used - If there is some sort of noise on the input signal, using some sort of low-pass differential and common-mode filtering may help reduce the noise.

    If they are willing to look at newer devices, the ADS1220, ADS1248, and the ADS124S0x are somewhat similar devices, with more example designs and sample code available. Again, I don't know anything about what they are doing to recommend another device. I still need much more information to help with this problem. I don't know what your customers system is or how they have it implemented. I don't know what type of noise they have. At this point, all I know is that they have noise in their system.


    Joseph Wu