question about thermistor scaling

Discussion in 'The Projects Forum' started by s3b4k, Nov 2, 2012.

  1. s3b4k

    Thread Starter Member

    Feb 15, 2010
    38
    0
    Hello there,
    In this article located here: http://www.embedded.com/design/prototyping-and-development/4023910/Temperature-Measurement-Technique

    they talk about thermistor scaling. and they provide a forumla that relates the input and the output through a non-inverting op-amp. I was just curious how do you solve the values for Rh,Ri, and Rf, from the article formula of the gain they provided. Is this supposed to be through guessing until it satisfies, the voltage you are interested in? thank you
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    Do you mean this figure 3 formula?

    [​IMG]

    Assuming you know the voltages, this is 1 equation relating 3 unknown resistances. So you need to specify 2 of those and then the 3rd is calculated. There is not one solution, there is a family of solutions. I'd use a spreadsheet to calculate the results (3rd resistance) for a table of two input resistances on the row and column headers.
     
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