Quantifying absorbance in LabView from amplitude.

I am currently trying to develop a way to convert amplitude to absorbance, and to be honest I am not sure if this can be done using LabView. Can this even be done?

Hi,
LabVIEW can do almost any math operation (spherical bessel functions, etc...). So, as long as you can develop an algorythm that is: absorbance as a function of amplitude (Y = Absorbance(amplitude)) you will be fine.
I assume that amplitude is a acquired signals value. Just work the algorythm, and then push the acquired data through your analysis routine before displaying on a graph, writing to a file, or whatever your use case is.
Let me know if you have any questions.
J

Similar Messages

Converting to real and imaginary from amplitude and frequency

basically there is a control of the amplitude and frequncy, so as to changes with resoect of real and imaginary

See the attachment, if this is what you require.
I ve enabled the Unit Label for the Freq control on the FP. Just rt-click & select to enable the Unit Label feature to dorectly key in the Deg [angle] value for the frequency parameter. Normally it takes frequency [or phase angle] in radians in LV.
- Partha
LabVIEW - Wires that catch bugs!
Attachments:
converting to real and imaginary from amplitude and frequency.vi ‏8 KB

How can i use labview.tlb to control Labview from an external application?

Hi,
I've been told by a labview engineer that i could use the file
labview.tlb located in the labview install folder to control labview
from an external application (in my case, a C# app). I'm using Labview
6.1 under Windows 2000. This article confirms that:
"ActiveX and LabVIEW"
http://zone.ni.com/devzone/conceptd.nsf/webmain/5401BE584FBAEECE862567C2006D36C7?opendocument
But i've not been able to find out how to use this file to achieve
what i want. I just want to be able to open/close labview, open/close
a vi, start/stop a vi, hide/show a vi from a C# application. The above
web page talks about activex but i really don't see the realtion
between activex and that labview.tlb file.
Is there so
mebody around who knows how to use that file? Why does NI
tell us that it's possible to do what i want to do but doesn't explain
how (or hides this info very well)?
Thanks

Hi,
> Hi I am fighting a similar problem and so far I found this: Calling
> LabVIEW from C++ Using ActiveX
>
> http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?>p_guid=B45EACE3E21356A4E034080020E74861&p_node=DZ52051&p_submitted=N&p_rank=&p>_answer=&p_source=External
Thanks for the link, i actually already found this link before. I've
found yesterday how to use Labview.tlb, just add it to the references
of the project, it was probably too easy for me at that time:-) But
now, i'm still stuck as there is no doc about using the interfaces and
classes of this activex to control labview.
The example given on your link is made is C++ and for some reasons,
the wrapper generated for Labview.tlb when i added it to my c# project
doesn't seem to expose the same
interfaces and classes as the one used
in the C++ example. I therefore can't use the C++ example in C#.
I've tried to do something like:
LabVIEW.ApplicationClass a = new LabVIEW.ApplicationClass();
Just this line causes labview to launch but then immediately throws an
exception: "Query interface for interface LabVIEW._IApplication
failed".
Does somebody knows how to use that control in C#/VB.NET ?

How to stop a while loop in LabVIEW from a C program

How to stop a while loop in LabVIEW from a C code

hi
I think by creating dll you can stop the while loop from your C program.For that you just create dll (Dynamic Link Library) for the VI which has that while loop.
Anyway can u please explain ur requirement clearly.

Import image to labVIEW from MSSQL

Dear all ,
i have some trouble about import the image from the SQL server by using labview
database connectivity toolset . How can i read the image in the Database ? as the image
is encoded by binary.
Thank all

hi mike ,
in fact , i want to import the image to the labview from the SQL database , but the image datatype is varbinary( Max ) ,
i don;t know how i can show this image and show it in the labview after i use database connectivity toolset to get the information of this image
my image is jpg.
is there any demo to do this ?
Thanks

To invoke an application exe built using Labview from python.

I am trying to invoke an application exe built using Labview from python.
I am able to invoke labview vi, send and receive data. But if I change the vi to exe, it doesn’t work.

This is more of Python. I can suggest you another way, if you can do those changes to your existing code.
This is what I do: If I have to communicate between 2 different platforms I use "File" as a communication medium (Simple method). So if you want to pass data to the LabVIEW code from python, write the data to the file from Python and read the data in LabVIEW and vice versa. I generally use *.ini files for this purpose.
The best solution is the one you find it by yourself

GPIB/LabVIEW from Java

I would like to develop software using the GPIB interface either directly or to access LabVIEW from Java to do so. I have seen bits and pieces of information posted on this exchange, but I have not seen anything about how to go about doing these things, just problems people are having doing it. I do not wish to do a large amount of work to be able to communicate with the GPIB controller, but I am willing to invest some time in it if I can get it working.
Thanks,
Naveen

A workaround could be the GPIB-232CT-A controller assuming that comunicating with the serial port it's simpler and much more documented.

ActiveX - LabView from C#

Hello,
I am creating a program in LabView from a already developed program in C# which uses ActiveX for controlling a laser machine.
The first thing I see in the program is the initialization of the ActiveX server and equipment system:
Laser = new LaserAxApp();
LaserSystem = Laser.System;
I found a refNum in labview with LaserAxApp but in their properties I found systems inside ILaserAxApp property. But also I found another refNum called laserengineLib.ISystem which is another class reference like AxApp.
which one should I choose to continue implementing my program from C#?
thanks in advanced,

Hello,
My name is Ed and I am with National Instruments Technical support. I’m happy to assist with this issue you are having, firstly I will need more information as to the overall system and just clarify what it is you are trying to achieve.
Am I correct in assuming that what you want is LabVIEW to communicate with C# through ActiveX (COM) and then C# also communicates to the laser machine through ActiveX and in this way you are able to control the laser machine from LabVIEW? Is the C# also a .dll file or an executable and do you also have access to the original source code or documentation as to the library/application code?
In the mean time I will continue to research in specifically communicating with C# from LabVIEW, as I understand it the process is very similar to that of .NET development for communication between C# and LabVIEW. The properties you are referring to I believe are that of classes in C# yes, where LaserAxApp could be the main object for the laser machine and laserengineLib.ISystem referring to a library which is used but this can only be confirmed by inspecting the C# code itself.
Here is one thread already solved referring to C# and ActiveX with LabVIEW which may be of some use to you:
http://forums.ni.com/t5/LabVIEW/Calling-ActiveX-dll-in-Labview/m-p/802573#U802573
Also included are two white papers which outline ActiveX in terms of the LabVIEW programming itself and the concepts behind these.
http://www.ni.com/white-paper/2983/en/
http://www.ni.com/white-paper/3831/en/
Regards,
Ed.

Way to acquire more than one sample at a time into Labview from cFP?

In reading data from my cFP into Labview I see that I can use the FP Read.vi but it only grabs one sample per call (loop iteration). In other devices, I could just use the AI Acquire Waveform.vi to grab multiple samples per call. Can I use this for cFP? Is there another way to grab more than one sample per call from my cFP? I'm just running it from a host computer, not using RT.
My specific problem is that I have two things I want to do with the same signal, one slow (PID control loop) and one fast (data logging). If I put the FP Read.vi in the same loop as the PID control, I can only get one sample in the time it takes the PID loop to run which is too slow. I'm trying to think of ways around this problem.
Thanks,
Hosehead

Hello Hosehead,
With FieldPoint there is no way to acquire more than one same at a time like
you can with NI-DAQ. With the FieldPoint read and write VIs
you can only read or write a single point at a time.
Please see the Sampling
Speed of FieldPoint Modules document for more information on cFP
acquisition rates. This document explains how channels are updated, how
often the data is updated, and what happens if you miss samples. Please
note that you will be able to acquire more samples if you are running your
application on the RT controller and not on your host computer.
If this does not answer your question, can you please post more data about the rate
you want your PID loop and your data logging loop to run at.
Regards,
Jesse O.
Applications Engineering
National Instruments
Jesse O. | National Instruments R&D

How can I collect and record data in LabVIEW from Sensirion Temperature/Humidity Sensor connected to myRIO?

The product documentation of the sensor and the datasheet is attached. Also Digilent MXP Breadboard's image is attached.
I've connected the sensor to myRIO using the starter kit's MXP breadboard: http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,1216&Prod=MXP-BB
The output of the sensor is in digital. My initial goal is to get digital output in form of 8 or 12 or 14 bits and then convert them to decimal numbers and record them.
Pin 1 of sensor is Data, which is connected to myRIO's connector A, DIO1 pin 13.
Pin 3 of sensor is Clock, which is connected to myRIO's connector B DIO5/SPI.CLK pin 21. According to the datasheet of the sensor, if VDD < 4.5V then Clock should be set to 1MHz.
Pin 4 of sensor is Ground, which is connected to Digilent MXP Breadboard GND pin.
Pin 8 of sensor is VDD, which is connected to Digilent MXP Breadboard +3.3V pin. Supply voltage range is 2.4-5.5V and recommended voltage is 3.3V.
I need to be able to send the following commands to the sensor from LabVIEW.
Measure temperature: 00000011
Measure relative humidity: 00000101
Then, myRIO has to wait for maximum 20 milliseconds (ms) for 8-bit measurement, 80 ms for 12-bit measurement, and 320 ms for 14-bit measurement.
Two bytes of measurement data will then be transmitted. myRIO as microcontroller must acknowledge each byte by pulling the DATA line (pin 13) low. All values are Most Significant Bit (MSB) first. Note that for 8-bit result, the first byte is not used. Finally, myRIO has to terminate the communication after the measurement data Least Significant Bit (LSB) has been received by keeping ACK bit, which is the LSB bit, as high.
Attachments:
Digilent MXP Breadboard.jpg ‏96 KB
Sensirion-Temerature-Humidity-Sensor-Documentation.pdf ‏136 KB
Temperature-Humidity-Manufacturer-Datasheet.pdf ‏323 KB

Have you searched the forum?
http://forums.ni.com/t5/LabVIEW/Sensirion-sht7x-labview/m-p/350958/highlight/true#M179022
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

Error in Calling a dll built in labview from Matlab standalone

hello,
The problem I encountered is in the use of the math interface toolkit. I
created a dll which performs data fitting using a labview vi which i converted into a dll using the
math interface toolkit.
This dll is then called from a standalone matlab program. It works fine in the computer where I
create the matlab standalone program and labview dll. Howerver when i export to another
computer the matlab part runs fine but an error is reported when it tries to
call the labview created dll.
"One or more output arguments not assigned during call Parfit.dll"
The files related to this problem in the math interface toolkit (the labview vi, the corresponding dll and the matlab .m and .fig files and the standalone exe are in the attachment and named MathITproblem.zip
The matlab run time engine(for matlab 7) and labview runtime engine(ver 7.1) must be installed for this matlab file to run. the run time engines are downloadable from the web.
Does any one know the source of this error or encountered it before?
thanks
Attachments:
MathITproblem.zip ‏1263 KB

Hi Srinivas,
Just another note, I noticed that the Math Interface Toolkit version (MIT) 1.0 is not compatible with LabVIEW 7.1. You’ll need version 1.0.1. of the MIT toolkit in order for it to work with LabVIEW 7.1.
The LabVIEW 7.0 lvanlys.dll is also attached. I had to rename it with a .txt extension, so you’ll want to delete the extension.
Kileen
Attachments:
lvanlys.dll.txt ‏516 KB

Call function in LabView from a DLL, then access global variable from DLL

I have created a DLL in LabWindows with a function and a structure. I want to call the function from within LabView and then access the global structure. I am able to call the function from the DLL with a "Call Library Function Node" and can access the return value, but I cannot figure out how to access the global structure. The structure is declared in the DLL header file with __declspec(dllimport) struct parameters.
Is there any way of accessing this structure without using the Network Variable Library?
Solved!
Go to Solution.

dblok wrote:
When you say "access to" or "the address of" the global variable, do you mean to pass the variable as an argument to the function call in the DLL? If so, then I was not really sure how to pass a cluster from LabView by using the "Call Library Function Node".
Yes, that's exactly right. I would include a pair of helper functions in the DLL to read and write the global variable. Alternatively you might write separate helper functions for each field inside the global structure, depending on the number of fields and whether you want to do any validation on the values.
You can pass a cluster by reference to a function that expects a struct by setting the parameter to Adapt to Type, so long as the cluster does not contain any variable-length elements (strings or arrays). The cluster needs to match the struct exactly, and sometimes that involves adding extra padding bytes to make the alignment work. Variable-length elements in LabVIEW need to be converted to clusters containing the same number of elements as the struct definition (for example, if your struct contains char name[12], you would create a cluster of 8 U8 values, and you could use String to Array of Bytes followed by Array to Cluster to convert a LabVIEW string into that format). If the struct contains pointers it gets more complicated, and it may be easier to write functions in the DLL to access those specific elements individually.
If you can't get this working or need help, post your code and an explanation of the error or problem you're seeing.
EDIT: it is also possible to include a single function in the DLL that returns the address of the global variable, which LabVIEW can then use to access and modify the data, but that's more complicated and likely to lead to crashes if you don't get the memory addressing exactly right.

Calculate time difference in Labview from excel file

I am reading in values from a excel files, the file contains date and time data in one cell, then either an On or Off value in the cell next to it. I would like to find the time difference between the on and the off cycles. The VI I have so far brings in the Excel file but I don't know how to subtract the dates. Any help would be appreciated. I have attached the vi and hopefully I can attach and example excel file.
Attachments:
Hobo Import.vi ‏156 KB

Hi Bryan!
I made a small VI (in LabVIEW 7.1) that converts to strings (of your format) to timestamp datatype and then subtracts them resulting in a difference measured in seconds. There might be a more optimal way to do this in your application, but I thought I'd at least try to contribute. Also, notice that there is a Y3K bug in there :-)
Hope this helps!
Travis H.
National Instruments
Travis H.
LabVIEW R&D
National Instruments
Attachments:
FormattoTimeStamp.vi ‏38 KB

Call compiled LabView from Delphi

Argh! I've done this already, but try as I can, I can't remember how, nor can I find my simple example!
I have a Delphi program that needs to communicate with my LabView app. The LabView app will be compiled into a standalone executable using the LabView (V7.1.1) Application Builder, as the target machines will not have LabView installed; hence, I can't take the approach of automating LabView.
For discussion purposes, the LabView app has a string control and a "go" button as controls, and a string indicator for indicators. The Delphi client supplies an XML fragment as a text string to the LabView app's string control, then "hits" the go button. The LabView app then processes the XML fragment, and outputs the results to the string indicator.
The LabView app is contained in a VI that has the aforementioned controls and indicator as input and output terminals, and has been compiled into an application with the "Enable ActiveX server" option selected. The Delphi app is built using Delphi 2007 for Windows.
How exactly do I import the LabView app into the Delphi programming environment? I've tried many things, have gotten close, but I'm not sure if I've got it right. I can connect to the LabView app, in that running the Delphi app starts up the LabView app, but I can't access the VI's controls or indicators.
How do I access the VI's controls and indicators from Delphi?
How do I simulate a button press?
This is very frustrating, as I had prototyped this six months ago!
Thanks for any help!
-Bob

Hi Donovan,
donovanb wrote:
Hi Bob,
You can use LabVIEW as an ActiveX Server, and thus expose properties and methods to ActiveX client applications, such as the Delphi app you're referring to. You can read and write front panel controls/indicators through the LabVIEW ActiveX Server interface, and it seems like this is what you are looking for.
Yes, that is exactly what I am looking for! Right now, I can only "see" a few, very generic methods, such as the GetVIReference() function in my second post. What I don't get is what to do with my "newapp" variable; how to I access the front panel controls and indicators?
Looking back at my second post, it seems the VI.Call may not really be the right thing to do, is that right? I have demonstrated to myself that the newapp.Connect call starts the LabView app - so then, I suppose the VI.Call is illegal, as the VI is already started - is that correct?
So I'm guessing that, after newapp.Connect, all I need to do is read/write the front panel controls/indicators, right?
But how?!!!
I'm not aware of a way to insert a LabVIEW front panel into an ActiveX container in another application, but even if you could, you would still need to use the ActiveX Server interface to actually access the data by the rest of the Delphi program.
That would be cool, but not necessary. Probably, I'll end up bringing the LabView app to front, and just using its front panel as is. That said, if someone know how...
The LabVIEW application doesn't even need to display the front panel, but can instead be called by the Delphi program, run in the background, and be polled/updated when needed by the Delphi application.
That's the other possibility...
Thanks!
-Bob

Adding an "IMAQ Image.ctl" to the "Display State.ctl" of an XControl prevents LabVIEW from creating a probe of "Display State.ctl"

I am working on an extended IMAQ Display control using LabVIEWs XControl capabilities.
I need a copy of the original image passed to add some overlays which must not affect the original image. To achieve this I am creating a backup image in the "Init.vi" and deleting it in the "Uninit.vi". I am storing the reference of this image in the "Display State.ctl" which is part of every XControl.
As soon as I am adding an "IMAQ Image.ctl" to the Display State cluster, it is no longer possible to generate a probe of the Display State cluster for debugging purposses. I am always getting the message: "Failed to load or create probe."
Deleting the "IMAQ Image.ctl" from the cluster makes the probe working again.
Is it a bug or am I doing something wrong?
I am working with LabVIEW 8.5 and Vision 8.5.
Regards
Ingo Bartsch

Hello Mr. Bartsch,
is it possible for you to post a small example to reproduce the behaviour? It would be helpful to get a description in which way you use the typedef files.
I found a example/knowledge base where some informations were included to XControl and LV but not with Vision.
http://digital.ni.com/public.nsf/allkb/1DC1ADD2A136DA298625712C00635758?OpenDocument
Best wishes
Jan Kniewasser
Jan Kniewasser | Applications Engineer | Tel.: +49 89 7413130 | Fax: +49 89 7146035

Quantifying absorbance in LabView from amplitude.

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