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ptc-50087411-Visitor
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March 12, 2013
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Electronic boards design: assessment of the component tolerances

  • March 12, 2013
  • 3 replies
  • 9213 views

I'm using Mathcad prime 2.0 (express version) but the question can be solved using premium version.
I would use Matcad to study the effect of the tolerance of the components I choose on the electronic circuits that I projected:
suppose, for example, you have a resistive divider formed by R1 and R2 powered from Vcc ..
we know that the voltage of R2 is:
f(Vcc, R1, R2): = (Vcc / (R1 + R2)) * R2

I want to ask Matcad which values ​​(maximum and minimum) can f() assume if
R1 has a nominal value of 1000, with a tolerance of 1% (therefore can have a value from 990 to 1010)
R2 has a nominal value of 2000, with a tolerance of 1% (therefore can have a value from 1980 to 2020)
The right way would be to use the function minimize () but I can not figure out how to properly set up the command

Thank you

Best answer by Werner_E

Find attached a version which (I hope) works in Prime Express, too.

EDIT: No, it can't work in Express as Express does not allow for programming

It uses two custom function: The first creates a vector of values given nominal value, tolerance and number of intervals. The second routine was a bit tricky to write. It takes a function and a vector of arguments and cycles through all the arguments finding max and min. The function has to be one with only one argument being a vector. This is necessary mainly because we are not allowed to write functions with a variable number of arguments.

 

Hope the attached sheet helps. You can apply this method to more complicated expressions with more than only two restistors, too.

 

MaxMin1.png

3 replies

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
March 12, 2013

See if this helps.

W
Werner_E25-Diamond I
25-Diamond I
March 12, 2013

I fear, if he is only using the Express version of Prime he will not be able to read that worksheet and even if, he will not be allowed to use solve blocks.

J
jkucan5-Regular Member
5-Regular Member
March 12, 2013

Here is a version in Mathcad Prime 2.0. Minimize and Maximize are premium functions, and require a license. Use a trial license.

    P
    ptc-50087411-VisitorAuthor
    1-Visitor
    March 14, 2013

    Many thanks for the answer, I get this work using a 30days trial version, thankyou very much

    W
    Werner_E25-Diamond IAnswer
    25-Diamond I
    March 12, 2013

    Find attached a version which (I hope) works in Prime Express, too.

    EDIT: No, it can't work in Express as Express does not allow for programming

    It uses two custom function: The first creates a vector of values given nominal value, tolerance and number of intervals. The second routine was a bit tricky to write. It takes a function and a vector of arguments and cycles through all the arguments finding max and min. The function has to be one with only one argument being a vector. This is necessary mainly because we are not allowed to write functions with a variable number of arguments.

     

    Hope the attached sheet helps. You can apply this method to more complicated expressions with more than only two restistors, too.

     

    MaxMin1.png

      P
      ptc-50087411-VisitorAuthor
      1-Visitor
      March 14, 2013

      Many thanks for the answer, thankyou very much

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