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Ocean/Calculator expressions and their units

MicheleA

Hi all,

I know it's not advised to put more than one questions per post, however I hope I'll structure this such that there won't be no confusion.

Main Topic

I am defining some expressions I would like to assess in my designs. To this end, I use the calculator in conjunction with some "ocean" script...Actually I just write expressions and define variables on a plain text file, but the idea is to expand on that with plotting functions and maybe output to file.

So let's say I have an AC sim. I then define some curves as follows:

 

twoPi = 44.0/7.0

vtank = VF("/tank_pos")-VF("/tank_neg")

itank = IF("/Vgen/MINUS")

icap = IF("/Cprobe/PLUS")

icapfix = IF("/Cfprobe/PLUS")

iind = IF("/Lprobe/PLUS")

runfreq = xval(vtank)

Ytank = itank/vtank

Zcap = vtank/icap

Zcapfix = vtank/icapfix

Zind = vtank/iind

cap = 1/(-twoPi*runfreq*imag(Zcap))

 

Now, it all works good if I copy/paste these definitions in the CIW, then ask --> plot(cap)

The issue I have with this is that now the Y-axis shows "freq" units...

cap value in femtohertz?

I observed that runfreq, defined as xval, is still correct. But if I do 1/runfreq, what I get is something with units of 1/(1/Hz), instead of s.

So probably here's where it loses it. Anyways, I see two possibilities here:

 

  1. I am doing it wrong
  2. I am doing it right

 

If 1 holds, then what's the right approach for something like this?

If 2 holds, do I have a way of "forcing" units onto expressions?

--------------------------------------------------------------------------------------------- END ----------------------------------------------------------------------------------------- 

Side Topic

 I find it more comfortable to write my expressions in the text editor rather than inputting them in the output definition box of ADE or ADE-XL. Is there a way of having the environment read my definitions as a file, and then just output the final expressions? In the (simple) case at hand, I would have defined all expressions as above, and plot them either from the CIW or directly from the file...

 

Thanks for your help!!

 Michele

Parents

  • Hi Michele,

    Looks as though I was not paying enough attention to the picture. The freq is the axis name not the units. I don't quite understand how the name ended up as freq - my experiments (I didn't do exactly the same as you) didn't end up with freq as the name - I'm guessing that it's coming from the xval() - the y-axis in that case would have a name of freq but I don't see how that would propagate through - normally the axis name doesn't persist through calculations as it would almost always be wrong otherwise.

    Anyway, rather than me writing an abSetName() function - actually it would be tricky to register this with the calculator because presumably you'd want freeform entry for the axis name rather than a cyclic field of predefined units, and if I use this way of registering the function it wouldn't surround the typed in name with quotation marks - not impossible to sort out, but I'm a bit pushed for time - I can show you how to set the attribute directly.

    drSetWaveformYVec(cap)->name=nil  ; erases the name, or you could use:
    drSetWaveformYVec(cap)->name="Cap"

    BTW, looking at your original code, I see you're calculating 2*pi as 44.0/7. I know that's only a 0.04% error, but you can do instead:

    defMathConstants('const)
    twoPi=2*const.PI 

    That's accurate to about 14 digits...  which is probably sufficient!

    It would probably be worth submitting a testcase to customer support so we can investigate (probably one of my colleagues, since I'll be on vacation after the end of this week) why the axis name is ending up as "freq", since it does seem a bit strange to me.

    Andrew.

Reply

  • Hi Michele,

    Looks as though I was not paying enough attention to the picture. The freq is the axis name not the units. I don't quite understand how the name ended up as freq - my experiments (I didn't do exactly the same as you) didn't end up with freq as the name - I'm guessing that it's coming from the xval() - the y-axis in that case would have a name of freq but I don't see how that would propagate through - normally the axis name doesn't persist through calculations as it would almost always be wrong otherwise.

    Anyway, rather than me writing an abSetName() function - actually it would be tricky to register this with the calculator because presumably you'd want freeform entry for the axis name rather than a cyclic field of predefined units, and if I use this way of registering the function it wouldn't surround the typed in name with quotation marks - not impossible to sort out, but I'm a bit pushed for time - I can show you how to set the attribute directly.

    drSetWaveformYVec(cap)->name=nil  ; erases the name, or you could use:
    drSetWaveformYVec(cap)->name="Cap"

    BTW, looking at your original code, I see you're calculating 2*pi as 44.0/7. I know that's only a 0.04% error, but you can do instead:

    defMathConstants('const)
    twoPi=2*const.PI 

    That's accurate to about 14 digits...  which is probably sufficient!

    It would probably be worth submitting a testcase to customer support so we can investigate (probably one of my colleagues, since I'll be on vacation after the end of this week) why the axis name is ending up as "freq", since it does seem a bit strange to me.

    Andrew.

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