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J
JohnTesko1-Visitor
1-Visitor
March 16, 2013
Solved

Can not explain error using lsolve function

  • March 16, 2013
  • 2 replies
  • 3859 views

Help!

I am trying to solve a set of simultaneous equations (25 variables) and I am not getting the results I am expecting. I have compared my MathCAD solution to bothe actual results and a PSPICE simulation.

I have distilled my problem to a much simpler example which I have enclosed and I cannot determine why the results do not match.

I have respresented the circuit as a simbple resitsor divider then added a simple low pass filter. With a frequency of 0 Hz (s=0) or a DC operationg point, I have represented the capacitors as an open circuit (Rcap = 1 / C*s). Since there is no current through RR3 or RR4, I know the results should be the same but with only RR3 in the equations, the results work, but when I add RR4, the results do not match.

Best answer by AlanStevens

You have a sign wrong! C3 should be negative.

Alan

2 replies

V
ValeryOchkov24-Ruby IV
24-Ruby IV
March 16, 2013

Why do you use a program? It is not a function. You cannot see results!

NotProg.png

J
JohnTesko1-VisitorAuthor
1-Visitor
March 18, 2013

The use of a function is just the nature of my final analysis. Since I will be running a Monte Carlo analysis (10,000 iterations), it is easier to put this into a function. Guess the next time I will just use equations first then place into function after I am satisfied with the results.

A
AlanStevens19-TanzaniteAnswer
19-Tanzanite
March 16, 2013

You have a sign wrong! C3 should be negative.

Alan

J
JohnTesko1-VisitorAuthor
1-Visitor
March 18, 2013

Alan,

Guess I was too close I did not see it. Now all I have to do is find the wrong sign in my complex analysis.

Thanks

W
Werner_E25-Diamond I
25-Diamond I
March 18, 2013

Wouldn't a solve block (avoiding error-prone manual rearranging of expressions) be more convenient?

lsolve1.png

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