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Offline Bocato  
#1 Posted : 19 January 2020 00:34:50(UTC)
Bocato


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Hi Everyone!

I am having some issues with graph indexed values in SMATH.

I am currently attempting to copy this app note here:
APP NOTE

In an attempt practice my smath.

My file may be found here V2_Input_Filter_Test.sm (82kb) downloaded 18 time(s).

I am currently stuck on attempting to replicate page 14-15 of the TI APP note.

this boils down to 3 questions:
[list]
  • While i am attempting to define an index value, i get a persistent error even though the equation solves fine
  • I am still unsure as to how to what is the proper syntax on how to graph the transfer function
  • I am struggling to understand how why my new filter impedance is not graphing

    Thank you all in advance!
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    Offline Razonar  
    #2 Posted : 19 January 2020 13:06:46(UTC)
    Razonar


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    Hi. Your issue is very small: you put some assignment 'j:=' in the sub-index, not globally.

    V2_Input_Filter_Test.sm (81kb) downloaded 28 time(s).

    Best regards.
    Alvaro.
    thanks 2 users thanked Razonar for this useful post.
    on 19/01/2020(UTC),  on 20/01/2020(UTC)
    Offline Jean Giraud  
    #3 Posted : 20 January 2020 16:17:13(UTC)
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    Originally Posted by: Bocato Go to Quoted Post
    I am struggling to understand how why my new filter impedance is not graphing

    Does it plot on your SS version ?

    Does it work.PNG

    V2_Input_Filter_Test [or like tis in red].sm (70kb) downloaded 14 time(s).
    Offline Bocato  
    #4 Posted : 21 January 2020 05:06:49(UTC)
    Bocato


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    Originally Posted by: Razonar Go to Quoted Post
    Hi. Your issue is very small: you put some assignment 'j:=' in the sub-index, not globally.


    This is interesting to me... I saw that you were able to make the Z2_j variable match the Z1_j however whenever I attempt to re-type the Z2_j definition as soon as I imput the 1/(s_j * Cin) statement it puts that "j" in the sub-index and doesn't allow me to edit it in a meaningful way.

    So far the only way I have found to fix this is to put in like so: Z2 = "equation here"

    Then once I have the equation finished inputting the defining equation, I go back to the Z2 equation and make it into a vector element, i.e. Z2_j = "equation here"

    Must be a "feature" lol.
    Offline Bocato  
    #5 Posted : 21 January 2020 05:53:23(UTC)
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    Originally Posted by: Jean Giraud Go to Quoted Post
    Originally Posted by: Bocato Go to Quoted Post
    I am struggling to understand how why my new filter impedance is not graphing

    Does it plot on your SS version ?



    When I downloaded the version that had those edits it showed that exact graph that you have posted.

    However, whenever I leave the values as i had them without vectoring them get the expected graph, which matches the TI app note. (see picture)

    [img=https://imgur.com/a/LHeHWzp]Input_Impedance_Graph[/img]

    Now what really confuses me the Transfer function plot looks so different. I input it as the App note stated however the graph seems "negated" as opposed to what I would expect.

    [img=https://imgur.com/a/962lZe5]Questionable Transfer Function[/img]

    [img=https://imgur.com/a/JDbyfBk]Proper Transfer Function[/img]


    Any Ideas Ya'll?

    Thanks in advance,
    Carlo
    Offline Jean Giraud  
    #6 Posted : 21 January 2020 16:35:03(UTC)
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    Originally Posted by: Bocato Go to Quoted Post
    Any Ideas Ya'll?

    Same as the other one ... see reply.
    Can't get that picture ?
    Offline Razonar  
    #7 Posted : 22 January 2020 21:07:02(UTC)
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    Hi Carlo. You take twice log10. Just augment log10(f) and LC.filter.

    Best regards.
    Alvaro.
    Offline Jean Giraud  
    #8 Posted : 23 January 2020 00:32:49(UTC)
    Jean Giraud

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    Originally Posted by: Bocato Go to Quoted Post
    I am still unsure as to how to what is the proper syntax on how to graph the transfer function

    1. This is not XFR [Transfer Function], simply impedance.
    2. Dimension the components wrt SI system [see TI values]
    4. More help, re-post page 1 working from this document
    5. Your version is older than SS 6179 ...
    it does not have page # associated with the cursor.

    HELPED_Input_Filter_Test_V1 ... first graph doctored NEW.sm (246kb) downloaded 18 time(s).
    Offline Bocato  
    #9 Posted : 23 January 2020 03:12:50(UTC)
    Bocato


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    Originally Posted by: Razonar Go to Quoted Post
    Hi Carlo. You take twice log10. Just augment log10(f) and LC.filter.

    Best regards.
    Alvaro.


    Hi Alvaro,

    I believe that is what I did? (seriously asking here) See picture

    Offline Razonar  
    #10 Posted : 23 January 2020 08:09:22(UTC)
    Razonar


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    Hi. Not in that plot, in the previous:

    Bad: Two logs:

    twice.jpg

    Ok: One log:

    one.gif

    This other have the same shape, and seems to have the same values than the mathcad plot in the TI app note. Notice that this plot is log only in the x-axis, and the y axis isn't in the log scale in the plot just because you're plotting in dB

    mcplot.gif

    The last plot is log in both x and y axis. See the difference in the green lines. So, you correctly take there here log for both axis

    mcplot2.gif

    smplot.jpg

    Best regards.
    Alvaro

    Edited by user 23 January 2020 08:13:04(UTC)  | Reason: Not specified

    thanks 2 users thanked Razonar for this useful post.
    on 23/01/2020(UTC),  on 25/01/2020(UTC)
    Offline Jean Giraud  
    #11 Posted : 23 January 2020 15:37:25(UTC)
    Jean Giraud

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    Originally Posted by: Jean Giraud Go to Quoted Post
    1. This is not XFR [Transfer Function], simply impedance.

    You can de-confuse yourself ...
    XFR are always Sigmoid shape, no matter the order of the system.
    They belong to Laplace domain system.

    Inst_XFR 2nd [XFR nth].sm (251kb) downloaded 17 time(s).

    Offline Bocato  
    #12 Posted : 29 January 2020 06:26:59(UTC)
    Bocato


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    Thanks to Jean and Razonar I believe we can close this thread up! At least as it pertains to graphing indexed values.

    The resulting file may be found here for reference:
    HELPED_Input_Filter_Test_V1.sm (88kb) downloaded 18 time(s).

    I have opened a thread here:

    Log based X and Y graph thread

    This will be an attempt to get my graphs to look more like the following


    But hopefully without that horrible green.

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