PV cell equation error in formula node

Hi! I am currently building a PV system simulation in LabVIEW with maximum power point tracking, and I'm trying to make this VI work using the formula node but I can't run it due to an "array indexing problem". The VI is based on the LabVIEW's toolkit for IV characterization using the equation for the PV cell current. I added the XY graph to graph the current and voltage from the equation. I'm really new to LabVIEW, so any suggestion will be greatly appreciated. I have attached the VI I'm building.
Solved!
Go to Solution.
Attachments:
eqn_based.vi ‏11 KB

Hi spectre,
the formula not cannot calc with arrays the way LabVIEW does:
(Check for correct computation against given formula...)
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Similar Messages

Error on Formula Node :Error on line 1 is marked by a '#' character:

Hey!!
This is a part of my prog..
Whats the problem with the prog?
Error on line 1 is marked by a '#' character: "y=[#uvl*50+(ul+ull+utlll)*40+(um+umm+umm"
Attachments:
Formulanode.vi ‏7 KB

you did not define "n" or "d". You can declare them in the formula node code, or even easier, just add outputs with these names.
(What is your obsession with formula nodes, why not use wires instead? This is LabVIEW! )
LabVIEW Champion . Do more with less code and in less time .
Attachments:
Formulanode1MOD.vi ‏7 KB

Labview. Writing an equation inside a formula node

How would I write this equation chl= (4.9467*mv) - 0.3239 inside a formula node? Thanks
Solved!
Go to Solution.

You don't even need a formula node. An expression node would suffice.
LabVIEW Champion . Do more with less code and in less time .

Formula node error

Error using formula node with non-linear fitting VI.
I am using LV 2011 on windows XP.
Using Nonllinear Curve Fit.vi. I have used this before successfully.I am using the "formula string" instance of this polymorphic VI. When I run my program using the formula string "b0+b1*x", it runs fine and give sensible results. When I use the formula string "b0+b1*x+A1*x^2" I get the error message "Error -23083 has occurred at an unknown location. Analysis: Bracket problem at the end."
Attached screenshots show part of the block diagram that wrorks (lv0.bmp) and ppart of the block diagram that does not work (lv1.bmp).
Thank you.
Attachments:
lv0.jpg ‏23 KB
lv1.jpg ‏39 KB

Thank you Dennis. It turns out the "caret" ("^") operator is OK here, and is raising a number to a power, as desired. The problem was that I used an uppercase letter in a variable name. Not allowed! Nor can variable names have have two letters, although that wasn't the problem in my example. (It was a problem in some of my other attempts.)

LV 6i: Serious Formula Node problem!

I have found a "serious" problem converting VI from LV 5.1.1 to 6i:
I have same "big" equations for density calculation with upper 65 coefficients
and 3 o more inputs variables.
Everything goes well and fast in 5.1.1, when I open this VI in LV 6i there
is automatically conversion
of exponential symbol (from "^" to "**") with non apparent problem,
but the result of equation is WRONG, very, very incorrect (from 0 in 5.1.1
to same negative milliard...).
I tried with more different equations and the results are similar...
For the last: when I re-convert my VI in version 5 and run it in LV 5.1.1
everything re-work PERFECTLY! Strange.
Have I found a "terrible" BUG?
Someone have found the same problem?
Do you have some ide
a?
I will wait some news from you.:-)
Thanks for reading this LONG news.
Bye, bye.
Alfio.

"Alfio" wrote:
>>I have found a "serious" problem converting VI from LV 5.1.1 to 6iI have
same "big" equations for density calculation with upper 65 coefficients>and
3 o more inputs variables.>Everything goes well and fast in 5.1.1, when I
open this VI in LV 6i there>is automatically conversion>of exponential symbol
(from "^" to "**") with non apparent problem,>but the result of equation
is WRONG, very, very incorrect (from 0 in 5.1.1>to same negative milliard...).>I
tried with more different equations and the results are similar...>For the
last: when I re-convert my VI in version 5 and run it in LV 5.1.1>everything
re-work PERFECTLY! Strange.>Have I found a "terrible" BUG?>Someone have found
the same problem?>Do you have some idea?
>I will wait some news from you.:-)>Thanks
for reading this LONG news. >Bye, bye.>Alfio.
Hi Alfio
Some times ago I had a simmilar problem but with labview 4.x. My equation
in the
formula node was (and still is) very large too but the problem was related
with the
x^2 terms. When these terms were changed with x*x the vi worked fine. Very
strange.....Also, this problem did not appear with small equations. Try a
smaller equation and see what happens. And more: with LV 5.1 (I am using
this version)
there is no problem.
Good luck.
Ricardo.

Updating equation in formula node from a string or text file

Is it possible to have a calculation performed based on an equation stored in a string (read from a text file). I am guessing not because the equation would need be compiled but thought I would ask.

Hi,
it depends on how complex the equation is.
Rather than using a formula node, you could use the eval formula node vi instead. (Functions->Analyze->Mathematics->Formula), but you may needs to re-organise the text formula a little.
Assuming you're using not the base package, and atleast LabVIEW version 6.1 that shouldn't be a problem.
Hope that helps.
Sacha Emery
National Instruments (UK)
// it takes almost no time to rate an answer

Formula Node error: left brace required ???

Hi,
I'm trying to use a formula node to do a simple line calculation. However I'm receiving this error and I'm not sure why.
Formula Node: left brace required
Error on line 1 is marked by a '#' character: "y = 0.0183*x -# 0.2982;"
I've tried replacing the y-intercept with a variable, but the same error results.
Anyone know what to do?
Thanks in advance.

What version of LV are you using? The formula:
y = 0.0183*x-0.2982;
works perfectly fine in V6.0.2...
Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

Formula node, keep getting errors

I am trying to integrate a formula node into an array, I keep getting errors and don't know why. Any ideas?
Thanks!
Solved!
Go to Solution.
Attachments:
trial7.vi ‏42 KB

That is a better attempt.
The problem is that you only defined your output y array to be a 1-D array. And your math on the input array is also acting like it is a 1-D array.
See the attached modification.
But your formula is simple enough that doing it in real LabVIEW code is easier and you don't have to deal with syntax problems of the formula node.
(Note, since I don't have your data, I couldn't run this, so it is possible there are errors.)
Attachments:
trial7MOD.vi ‏57 KB

Formula node error: missing left parenthesis

Hi guys
I am new on labview and i am strugling to right a bit of code.
I am using formula node and i keep getting the error as above on the title moreover it displays: Error on line 5 is marked by a '#' character: " for {# H = 00.00.00 to H = 06.00".
I am attaching my file so that if you can give me a hand you could have a brief look.
Thank you
Solved!
Go to Solution.
Attachments:
time_look up test.vi ‏14 KB

Hi inaslab,
still your formula node doesn't make sense: You still overwrite the value for H in the first FOR statement...
What you want is either an IF-THEN-ELSE or a SWITCH/CASE construct like "IF (H>=0 AND H<6) THEN...". Right-click the formula node, select help, select formula node syntax !
And I'm even more convinced a standard LV case structure will be much more reasonable here: just wire H to the selector input...
Message Edited by GerdW on 10-29-2009 11:29 AM
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Formula node error: missing left parenthesis

Im trying to compute a simple function in a formula node, I recieve the following errors:
Error on line 1 is marked by a '#' character: "X3=sin**#2(2*T);"
Error on line 1 is marked by a '#' character: "X5=(cos**#(2)(T);"

Has anyone else noticed the name of this guys VI ?
Thoric (CLA, CLED, CTD and LabVIEW Champion)

Formula node error: missing right parenthesis

Hi NI community,
I am working with the formula node structure for the first time and I came along this error which I can't fix.
It says it finds a # character, but the strange thing is that there is no character. Is there anyone who can help me with this one please?
Kind regards
Thomas Ruts
Solved!
Go to Solution.

You are missing a right parenthesis on your first long formula. It is in the last half of the formula. You have two left parenthesis, but only one right.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Why do I receive Error -23088 when using the Eval Formula Node.vi (LV6.1)?

Hi,
I want to evaluate formulas like x=v>20; with that vi. When typing the
same formula into an normal Formula Node I get the correct answer. When
changing the formula into x=v+20; the eval Formula node.vi works fine.
But whenever I try to resolve a boolean function like that mentioned
above, I receive that f****n Error! Why this? What can I do? Is the Eval
... .vi less powerfull than the normal node?
Thanks for your help,
Daniel

Joel A wrote:
> I think the boolean (binary) ops are the only difference between the two nodes.  I pulled this from the help:
> Formula Node and Expression Node Functions
>
> The following list contains the names of the Formula Node and Expression Node functions, and their descriptions. Except for the binary functions, you also can use these functions with <a href="gmath.chm::/Parser_VIs.html" target="_blank">Formula VIs</a>. All function names must be lowercase. You also can use <a href="mk:@MSITStore:C:\Program%20Files\National%20Instruments\LabVIEW%208.0\help\lvhowto.chm::/Precedence_of_Operators_in.html" target="_blank">operators</a> and the pi constant in Formula and Expression Nodes.
> Start at the help above, and see if you can find any helpful information.
>  
>  
> J
Thanks for help,
I solved the problem by using the "Parse Arithmetic Expression.llb" from
examples. You can modify it and add the operators you need..

Graph equation formula node problems

I am using LV6.0. I am having some problems regarding the formula in the formula node. I hope someone can help. The vi is attached
Attachments:
graph equation.vi ‏15 KB

Yes, that's right. Waveform graphs and charts always show data in this way. If you want to use your x-values as x-axis and the y-values as y-axis, you have to use the xy-graph.
Attached is a screenshot of the vi.
Hope this helps.
Thomas
Message Edited by becktho on 10-04-2005 12:32 PM
Using LV8.0
Don't be afraid to rate a good answer...
Attachments:
xygraph.JPG ‏175 KB

Formula node calculation error

Hi all,
I am expecting the output of formula node as the value of "c" input variable. but it outputs NaN. I am attaching jpeg file illustrating that.
Clarification would be appreciated.
Kousy
Attachments:
Formula 1.JPG ‏21 KB

Hi Kousy,
look at attached example...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome
Attachments:
Interpolate_threshold.vi ‏15 KB

Parenthesis in formula node

I'm using the formula node and it appears that parenthesis don't work. Is this correct? What is the order of operations?
The Formula Node Syntax page in the help is extremely brief and sparse, bordering on useless for anyone that doesn't already now what is going on. Is there a more thorough description of the Syntax anywhere?

Thanks Dennis,
The error is just an incorrect calculation.
I put together a simple node and parenthesis did work. So something else must be amiss. I stripped down my VI and equation and made two formula nodes implementing the same equation with and without parenthesis. One gives an exponential decreasing curve, the other a constant array. Where is the error?
Attachments:
parenth_ex.vi ‏49 KB

PV cell equation error in formula node

Similar Messages

Maybe you are looking for