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Interfacing industrial signals to microcontroller ADC

Discussion in 'Microcontrollers, Programming and IoT' started by Gergo, Jul 23, 2017.

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  1. Gergo

    Gergo

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    Jul 23, 2017
    As an assignment I have to design an industrial data acquisition system based on a microcontroller, using it's integrated ADC. Thus signal input range is limited to 3.3V. I am looking for a solution or reference design, to measure the common industrial transmitter outputs with my ADC. 4-20mA signals are easy to deal with. My main concern is voltage measurement of signals higher than 3.3V. I have been adviced to use a programmable gain amplifier which is capable of attenuation. Although I have doubts using it, one reason being is that I hardly find any out there. Any suggestion or reference design for such a system?
     
  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    It could be as simple as a voltage divider (resistive) with zener clamping for overload to bring the signal into the range of the DAQ device but much depends on what accuracy you're looking for.
     
  3. Minder

    Minder

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    657
    Apr 24, 2015
    Using the Picmicro range you can measure 5v analogue inputs.
    What level of analogue signal are you dealing with?
    M.
     
  4. Gergo

    Gergo

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    Jul 23, 2017
    A voltage divider was my original design. Then my teacher told me that it isnt accurate enough. I am planning to design the analog input of the DAQ to be able to measure common transmitter outputs. 4-20mA, 0-5V, 0-10V, +-10V.
     
  5. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Considering even the best quality multimeters rely on resistor networks to attenuate - before passing it to the ADC - the statement that a voltage divider 'isn't accurate enough' is bollox.

    Get your teacher to explain why he thinks this is the case.
     
    Arouse1973 likes this.
  6. Gergo

    Gergo

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    Jul 23, 2017
    Seriously I dont understand him either.
    In any case this is not going to be a professional DAQ device. I am just curious how would more experienced designers solve this. In the end I may go with 4-20mA and 0-10V using the divider. I found one PGA with attenuation function so it cant be a common solution.
    Anyways, thank you. I will definitely ask my teacher about what exactly he was thinking.

    .
     
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