Hello Everyone
I am new in Mathcad. I would like to plot "Bode Plot" from the given transfer function. I followed one of the attached reference ,but i stucked in between. Please help in this regard.
Please tell me if any other simplest way exist to do so.
ACCEPTED SOLUTION
Accepted Solutions
AlvaroDíaz wrote:
Sorry, can't tell you why, but I only rewrite your expressions, and then works. But have not idea why.
It's a sneaky one, Alvaro; one of the commonest errors that can't be easily diagnosed from a picture and needs a careful look even with a worksheet. sm is a literal subscript not an index. Note how the "Subscript" button highlights in the Style ribbon. The definition on the right has m as a vector index; it is slightly lower than the literal version of m but not sufficiently to make it clear. I'm not sure that it's worth the effort of lowering the index (given that the Subscript button highlights) ; I prefer the look of the literal subscript position anyway - it's just one more ambiguity in standard math notation and I'd prefer Mathcad (and other applications) to stick to the ISO (or, at least, have an option for strict ISO)..
Stuart
AlvaroDíaz wrote:
Sorry, can't tell you why, but I only rewrite your expressions, and then works. But have not idea why.
It's a sneaky one, Alvaro; one of the commonest errors that can't be easily diagnosed from a picture and needs a careful look even with a worksheet. sm is a literal subscript not an index. Note how the "Subscript" button highlights in the Style ribbon. The definition on the right has m as a vector index; it is slightly lower than the literal version of m but not sufficiently to make it clear. I'm not sure that it's worth the effort of lowering the index (given that the Subscript button highlights) ; I prefer the look of the literal subscript position anyway - it's just one more ambiguity in standard math notation and I'd prefer Mathcad (and other applications) to stick to the ISO (or, at least, have an option for strict ISO)..
Stuart
I'm not one that usually has much praise for Prime, but the difference between the subscripts is even more subtle in MC15 (almost invisible if the cursor is not in the expression)
MC15:
Prime:
Richard Jackson wrote:
I'm not one that usually has much praise for Prime, but the difference between the subscripts is even more subtle in MC15 (almost invisible if the cursor is not in the expression)
I agree, and I imagine that trying to make the distinction more obvious is one of the reasons that PTC changed the layout.
However, for normal scales it still takes a sharp eye to *notice* the difference, especially if one *knows* what the expression is supposed to be doing (it took me about minute of gazing at it to figure out what the problem was). Which means that it possibly isn't worth the effort and only ends up making indices look slightly awkward and increases the amount of vertical space that expressions take (and programs already eat up more than they need).
I haven't yet found a standard that makes any distinction between a descriptive subscript and an indicial one, except in the matter of typeface, where the convention is that descriptive subscripts should be in roman (upright) font whilst indicial ones should be in italic (eg, http://www.physics.nist.gov/cuu/pdf/typefaces.pdf). So if PTC want to take note of the standards, then they should put all subscripts at the same level and make the descriptive subscripts Roman. In the example below, from the referenced NIST document, the subscript a in loga is italic because it's a variable, but the e loge is roman because it's descriptive.
Stuart
Richard Jackson wrote:
Perhaps I misjudge them then. Guilty until proven innocent is what I say though
You are Judge Dredd and I demand my £5. 
... that's an idea. Maybe we could lock up the developers in an IsoCube until we get MDAs. 
SAMEER GARG wrote:
Hi Stuart
Thanks for your interest. I got what mistake i had done. I substituted m as a subscript but it should be in vector(M() option under Operation Tag in Menu). As i told i have been through one reference, I am not getting why exactly these complicated variables (N,r, wstart,wstop) they have used just for freq range. I can simply give using W=10,10...100. Can you please clarify for the same.
Hi Sameer,
The reason is that it's easier to change an individual variable than modify the range variable. In addition, you might want to use those variables elsewhere (eg, when limiting the plot ranges or testing the values at the end points).
The best reason, though, is probably maintainability and reuse. It's often easier for others using your worksheet (or even yourself at some future date ... like about 10 mins later if you're anything like me! 
) to work out what the 10 and 100 mean when they first start looking at the worksheet. You can also easily grab the whole set of equations across and use them in a different problem with a different range of values, and only worry about changing them once - job done!
On a Mathcad technical side, you wouldn't want w to be a range variable anyway. Only use range variables for iteration (where you generally want an integer) or for one-offs, otherwise use vectors; you can perform mathematical operations on a vector but you can't on a range variable.
In terms of the problem itself, I suspect that the expression for r should 1/(N-1) not 1/N - you get a proper decade log scale then. It's also worth looking up the logspace and logpts function, as they can make life easier for applications like this.
Also the bode plot should be in log scale..I mean X axis should be like 0.1,10,10^2,10^3....but I am getting something different.Please help in this regard.
In Prime 3.1, you need to click on each axis in turn and then choose Logarithmic scaling.
Stuart
Ah,
and all I see is that you appear/seem to be working with a version of Prime that I guess even PTC is only dreaming of......13.
Luc
SAMEER GARG wrote:
Hello Everyone
I have been through all suggestions. On that example it was working find but attached example its not working and again some error is coming. Please help me in this regard.<<Please see attached Problem1>>
Problem 1 is actually corrected by adding units to wstart and wstop.
Just as an aside, whilst the wm method works well in Mathcad, it might be slightly less meaningful to an average (but domain-literate) reader. It would be nicer to drop the indices and just have M(g,w) and w on the axes. You can achieve this by making M and P automatically vectorize their arguments.
Also I would like to make w_start and w_stop with Hz as a unit. When i used to do so i was getting an error.<<Please see attached problem2>>
Your new expression for G(s) contains a polynomial in s, which when expanded will result in an equation that has mixed powers of Hz. Dimensionally, this is disallowed as you cannot add seconds to seconds-squared. There are several ways of dealing with this: divide s by Hz when calling the G, divide s by Hz inside G and then apply the expression , divide each s in the expression by Hz, or expand the polynomial and divide each power of s by the appropriate power of Hz. See the attached worksheet.
Stuart
SAMEER GARG wrote:
Hi
Thanks a lot for valuable response. As per your suggestion i used to call the function from the plot with taking care of dimension. In lott of problem it worked fine but i am unable to proceed for given transfer function. Please help what exactly I have to do, @to take care of?
Look to the units! The Error Tracing facility points you back to an incompatible unit error - you've got RC+CC.
I don't know whether it's what you want, but I changed one of the capacitances to be Rdamp (and in the expression on the denominator) and this at least fixes the problem. You need to leave the units in the W(fm) expression, otherwise Q(f) becomes dimensionally inconsistent.
Stuart
Hello Stuart
Thanks a ton
. Finally i done with. There was a mistake in transfer function calculation. I solved that again and i got finally my expected result.
. Thank God from now onwords I will not confuse between subscript and Vector and also dimension consideration on plotting.
SAMEER GARG wrote:
Hello Stuart
Thanks a ton. Finally i done with. There was a mistake in transfer function calculation. I solved that again and i got finally my expected result.. Thank God
Excellent.
from now onwords I will not confuse between subscript and Vector and also dimension consideration on plotting.
Oh yes you will. The only reason we have fingers is to type the wrong thing, and the only reason we have brains is to remember to do all the things we said we never would.
http://www.murphys-laws.com/murphy/murphy-laws.html
Stuart
Hello Stuart
Thanks a ton. Finally i done with. There was a mistake in transfer function calculation. I solved that again and i got finally my expected result.. Thank God from now onwords I will not confuse between subscript and Vector and also dimension consideration on plotting.
