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I am designing a circuit, to use an ADC(mcp3008) to read voltage, current, and temperature sensors. I have a few questons about this, as I have never done this before.

  1. I am going to use single ended mode; Can I just plug in the sensor directly to the ADC, or does it need to go through some processing or filtering?
  2. I need to read voltages that vary from 90-108v the maximum voltage that my board can supply the ADC for Vref is 12 Volts. How can I read this high voltage?
  3. Are there any additional considerations that I should keep in mind to make my circuit as reliable as possible?

Thank you for your help!

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  1. Depends on the sensor output impedance, frequency content, and signal range. If the output impedance is high, you need a buffer. If the frequency content is too high for the ADC, you need a low pass filter. If the signal range is too small, you need amplification.

  2. Use a voltage divider to bring it down to the range in question, then buffer with an op-amp if necessary.

  3. Read about the ADC's input capacitance characteristics. I've written a blog entry that will help explain this. If you're repeating your samples slowly, it's not a big deal, but rapid sampling makes this important. The sampling time before ADC conversion is also important.

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    \$\begingroup\$ Thank you for your answer, this really clears things up! \$\endgroup\$
    – Reid
    Mar 24, 2012 at 5:36
  • \$\begingroup\$ Necro comment here, but I found the article super straight-forward and useful. \$\endgroup\$ Sep 12, 2012 at 23:39

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