cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Showing results for 
Search instead for 
Did you mean: 

Community Tip - Have a PTC product question you need answered fast? Chances are someone has asked it before. Learn about the community search. X

Asymptotic Bode Plot Issue in Mathcad Prime 7

Cornel
17-Peridot

Asymptotic Bode Plot Issue in Mathcad Prime 7

Obtaining the ASYMPTOTIC Bode plot for the following transfer function:

CornelBejan_0-1668698404973.png

CornelBejan_1-1668698482728.png

Mathcad Prime 7 result:

CornelBejan_2-1668698520669.png

CornelBejan_3-1668698604411.png

 

Why does the result in the Mathcad Prime 7 not look like it looks like in the figure in the example??
The idea is that I want the plot in Mathcad Prime 7 to look exactly like in the picture above, with straight lines and those corners, and not to bend corners Mathcad Prime 7 at w=2 and w=10.

Mathcad Prime 7 file attached.

 

1 ACCEPTED SOLUTION

Accepted Solutions
Werner_E
24-Ruby V
(To:Cornel)

To get the asymptotic approximations you simply have to replace in expressions like 1+j w the 1 for a zero (aka omit it).
For w -> infinity these 1's are neglectable.

Werner_E_0-1668706079851.png

Maybe this link additionally helps to understand: https://lpsa.swarthmore.edu/Bode/BodeHow.html

 

 

View solution in original post

5 REPLIES 5
Werner_E
24-Ruby V
(To:Cornel)

To get the asymptotic approximations you simply have to replace in expressions like 1+j w the 1 for a zero (aka omit it).
For w -> infinity these 1's are neglectable.

Werner_E_0-1668706079851.png

Maybe this link additionally helps to understand: https://lpsa.swarthmore.edu/Bode/BodeHow.html

 

 

Cornel
17-Peridot
(To:Werner_E)

Mathcad 15 result:

1.png

2.png


Mathcad Prime 7 result:

CornelBejan_4-1668758288427.png

 

CornelBejan_2-1668757901817.png

CornelBejan_3-1668757977993.png

 

At w = 10, let's say it's something more ok (even if it's not even right angle there at the intersection (as it kind looks like in Mathcad 15)), but at w = 2 why is not ok (only somewhere at w=~ 2.1 seems to be more ok/accurate)?

The same results, no matter where I put the greater than or equal sign (so that it also contains the end values ​​w=2 and w=10):

CornelBejan_0-1668759036458.png

CornelBejan_1-1668759084725.png

CornelBejan_2-1668759109966.png

 

CornelBejan_3-1668759167824.png

CornelBejan_4-1668759191254.png

CornelBejan_5-1668759217640.png


Mathcad Prime 7 file attached.

 

Cornel
17-Peridot
(To:Cornel)

@Werner_E I think I found the answer. At least that's how it seems to me so far, but I'll post if I find anything else...

 

CornelBejan_5-1668764504178.png

 

 

CornelBejan_6-1668764524426.png

 

 

CornelBejan_3-1668764470613.png

CornelBejan_7-1668764547775.png

 

CornelBejan_8-1668764658245.png

CornelBejan_9-1668764676351.png


Thank you.

 

ttokoro
20-Turquoise
(To:Cornel)

image.pngimage.pngimage.pngimage.png

Werner_E
24-Ruby V
(To:Cornel)

Yes, Mathcad (15-) is much better when it comes to autodetect suitable scales for the axes in a quickplot. Prime almost always requires you to manually adjust the scale to get useful values.
This seems to be what you did and it looks like it worked OK.

 

Normally you have a better control if you don't use a quickplot but rather define a range variable for the abscissa values (in Prime you often will still have to adjust the second axis value).
Unfortunately ranges are linear only and you would have to define a very dense range (resulting in quite many points in the plot) if you use a log scale.

Way out can be to define a vector with "logspace" as ttokoro had shown and then plot one vector over the other.

Top Tags