Multiplexer in LabVIEW 8.0

Guten Tag. Kann mir jemand sagen ob, und wenn ja, wo es in LabVIEW 8.0 einen Multiplexer gibt der in seiner Kanalzahl variabel ist?
Ich möchte damit einen digitalen Ausgangsport schalten dem ich nacheinander verschiedene Daten übergebe. Oder gibt es da eine andere Möglichkeit? Gruss

Hallo FloMAN,
wenn ich Sie richtig verstanden habe, dann kann man das recht leicht in einer Schleife mit Scheieberegister realisieren (s. Beispiel)
Bei den Bits in diesem Beispiel weniger wichtig, aber generell muss man zu dieser Programmierung noch sagen, dass man zu Gunsten der Performance hier auf eine While Schleife verzichten und statt dessen eine For Schleife bevorzugen sollte, dann weiss LabVIEW schon vor Start der Schleife, wie gross das Array werden soll und allokiert dementsprechend Speicher. Das sollte man natürlich vor Allem beachten, wenn man nicht nur Boolsche Werte ins Array schreibt, sondern Datentypen, welche mehr Speicher brauchen.
mfG
Ingo Schumacher
Systems Engineer Sound&VibrationNational Instruments Germany
Attachments:
do port.zip ‏7 KB

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MyDAQ, connect sensors with multiplexer in labview

I am quite new to labview so hope someone can help. What I am doing is to use NImyDAQ to connect 8 different sensors and show the output on labview. Since the myDAQ does not have enough input for 8 sensors, so I am using two 8 bits multiplexers to solve it.
Here is the question. How do the circuit draw in the labview which will make it works? I want to make an drop down button to select which sensor is connected and shown, therefore I need to output boolean value (0,1) to the digital input/output? I have try using case structure but seems difficult for me. Is there any example similar to what I am doing?
Attachments:
Idea_01.jpg ‏187 KB

What you mean by skiping the DAQ Assistant? Can you make a drag and drop diagram for an example? I have no idea how the drop down menu giving out numerical value then goes into the Digital input in NImyDAQ.

How can I use LabVIEW to ground floating SCXI-1520 channels (in order not to lose scanning capabilities from the multiplexer)?

Currently I am reading quarter bridge strain with several SCXI-1520s. When in MAX I noticed my values were no longer reading after a certain gage and as I attempted to troubleshoot, found out that the multiplexer in this module will not scan past any open channel (or if it does, channel results are not consistent) for a very logical reason. If I lose a gage, I usually lose any data from any subsequent gages which we really cannot afford.
Are there any suggestions programming in LabVIEW (right now i'm using NI-DAQmx with an analog task set up)so that each time my loop executes, the program will check for any open channels and either not collect that data or change the order of acquisition (i.e. place the open channels last on the scan list?
I'm open to anything that might be of help

Yes, by "open channel" i mean that there is no signal returning from the gage because it has broken off the structure or the signal to the terminal block has been disconnected somehow.
When I lose data, I'm referring to the data that is acquired on following channels. The behavior appears to be fairly random (which was a troubleshooting nightmare ) but usually if a channel is open, then that and those behind it in the scan order do not return any data. It returns a number like 10.357E-6 and I do not pick up any noise or fluctuations. As far as I understand, the multiplexer stops scanning at this point (open channel) because it has nothing to ground to and subsequently "hangs" - not (or randomly) scanning the following channels. I have gone through the bridge configuration and as of yet, have not figured out how to fix this using any hard-wiring techniques. I emailed NI, and was sent a library file to "ground the channels" but it actually resets the Analog input Task I have defined each loop.
I am new to NI-DAQmx so I do not know if this will alter any configurations I already have in MAX for NI-DAQmx. Will it override? I am concerned it will slow my loop time, and also I cannot see the code for this sub.vi so am a little skiddish about using it if i do not know if it can be tailored to my app.
What do you think? Am I on the right path?

Labview interfacing with a multiplexer

Hello,
I would just like some help with figuring out how to set-up Labview to interface with a multiplexer. On my ciruit board, I have an eight channel multiplexer which is connected to eight different-value resistors. What I would like is that on my front panel, there should be an drop-down control that allows the user to select any resistor that is connected to the multiplexer. So basically, Labview should be able to send binary information to the multiplexer, which would then select the appropriate resistor. I am fairly new with Labview and don't know how to go about this problem. Any suggestions will be appreciated.
Thanks

Hi,
All the adress and enable inputs are TTL compatible (the multiplexer that I'm using is the ADG608 from Analog Devices) and I am currently using the NI PCI-6036E/BNC-2110 starter kit. So, is there a way to implement the interface using this DAQ device? Can I use DAQmx to create a channel just as I would for a normal voltage signal? But I'm not sure how the interface will communicate with the multiplexer.
Thanks

Labview compatible low-budget multiplexer

Hello everyone,
I am trying to set up a device to automate some of the measurements in our laboratory, which will save a lot of time. Since I am on a budget I would need to know a very cheap source for a multiplexer that can be programmed with Labview. Can anybody recommend me sources?
Ideally I would need one 30 to 1 multiplexer and another one that can do 10 to 1. However, I could also create smaller batches if that would save money.
Many thanks,
Ralf

Hi pannepanda,
when you talk about "multiplexer" I thought you would need an external device that does the switching, so you would only need to communicate with that external device. The easiest possibility to drive a 30:1 multiplexer is by using 5 DOs…
Please state your needs with clear descriptions!
Do you need a DAQ card to measure up to 32 analog signals? Call your local NI sales representative!
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

How do I use AI triggers and counters in DAQ6020-E using LabVIEW 6.0

Hi:
I am new to LabVIEW and sorry for newbie questions. My questions are:
1. I want to use the 2 counters in DAQ6020-E to generate 2 continuous pulse trains(C1 and C2) at different frequencies(C1 @ 1k Hz and C2 @ 2k Hz)and I want to synchronize these 2(for example,they both start with positive edges), how can I accomplish that? should I use a software trigger or a hardware pulse trigger?
2. Followed from 1),there will also be 4 analog inputs(a0,a1,a2,a3) in the same VI. I want them to be triggered by two non-overlapping clock sigals phiA and phiB. phiA and phiB are created by C1 and C2, they both will have 25% duty cycle(with 1k Hz frequency) and are out of phase by 180 degree(thus they wont be bo
th high at the same time).I want a0 triggered by the postive edge of phiA, wait for 0.1 ms, take 1 sample,stop and wait for the next postive edge of phiA. Similarly, a1 will be triggered by negative edge of phiA(wait .1 ms and then sample), a2 by positive edge of phiB, and a3 by negative edge of phiB.
I want to know what pins in the 68-pin connectors corresponding to counter0 and counter1 output, and where should I hook up the triggering phiA and phiB to. Should I initialize them first in Measurement & Automation Explorer?
Thanks so much.
Alan

Hello Alan,
Thank you for contacting National Instruments.
Here are some answers to your questions:
1. You will want to use a harware pulse trigger. This pulse will be connected to the gate of both counters. When a rising edge is detected, both pulse trains will be output on the output pins of the counters. See example attached below.
2. It will not be possible for you to accomplish what you are asking with a DAQPad-6020E. E Series devices only have one analog-to-digital converter (ADC). This means that all 16 channels are multiplexed to a single ADC. This means that it will not be possible to sample(trigger) a0, a1, a2, and a3 simultaneously nor independently. Also, it is not possible to implement the 0.1ms delay from when the edg
e of the sample clock is detected. Here what you can accomplish:
1. You can use an external clock to sample(trigger)a single channel.
2. You can select if you would like the sample your signal on the rising or falling edge of your external clock(phiX).
3. You can use the output of one of the counters as your external sample clock.
I have attached two examples below. One of them generates a pulse train from counter 0. The other acquires analog data from channel 0 by using an external clock.
Here is a link to the DAQPad-6020E User Manual. The output pins for the counter can be found on pages 4-2 and 4-3: http://digital.ni.com/manuals.nsf/websearch/9B5442F668EB7C6B8625669F00743D24?OpenDocument&node=132100_US
Regards,
Bill B.
Applications Engineer
National Instruments
Attachments:
Generate_Pulse_Train_(DAQ-STC).vi ‏103 KB
Cont_Acq&Graph_ExtScanClk.vi ‏108 KB

How to acquire data through multiple channels in parallel using PXI 6070 E, PXI 4071 and LabVIEW?

Hi,
I am using NI LabVIEW, NI PXI 4071, and NI PXI 6070E to measure current through a variable resistance. Now, I am using one channel from SCB-68, but I want to add another channel in parallel so that I can have two resistors instead of one that I cam measure current through them.
I have attached a Pdf file showing the setup for hardware in use and LabVIEW code also.
Can anyone look at these files and give me guide lines or ideas that can help me resolving this issue, please.
Thanks in advance.
Best Regards,
Shaheen.
Solved!
Go to Solution.
Attachments:
IV copy for HS.vi ‏55 KB
Layout of NI Cards.pdf ‏248 KB

Your 4071 can only do one measurement at a time. Your DAQ cannot measure resistance either nor has it got any analogue inputs.
However, you could use a multiplexer and multiplex your 4071 DMM. This wont give you simultaneous measurements but can acquire data one after the other, the speed is obviously dependent on the multiplexer you choose!
Hope this helps.
Beginner? Try LabVIEW Basics
Sharing bits of code? Try Snippets or LAVA Code Capture Tool
Have you tried Quick Drop?, Visit QD Community.

Time Division Multiplexing and Processing Different Loops at the same time

Hi, I am new in Labview so you may find my questions too silly, sorry about that
I want to design an interface to control the test&measurement devices remotely. I have two desks and there are several devices on these desks. The real problem is to use two different devices at the same time. To do this I heard that I can use time division multiplexing. But I couldn't find enough information about it in Labview. Another advice I heard was to use a matrice and hold the on/off state of the devices in this matrice.
Where should I start the design to create such a system? Do you have any advices? Thank you in advance.
My basic GUI is attached.
Attachments:
InterfaceAli.zip ‏42 KB

As Mike pointed out you cannot communicate in parallel on the GPIB bus - unless you have separate buses for each instrument - and that defeats the purpose of a bus. I am not sure about LXI.
With regard to your VI:
1. Do not use global variables to pass your data around.
2. You should use the Array data type, not the Matrix data type. The Matrix data type in LabVIEW should only be used for matrix mathematical operations (linear algebra) which cannot be easily performed on the array data type. You have many more tools in LV to work with arrays.
3. The Event structure needs to be in a parallel loop. This is basic data flow. If you do not understand this concept, get some training, either though the online tutorials or through a class.
4. Use Value Changed events and place the button terminals inside the event case for that control.
5. The parallel loops need to have a Wait or some other function which causes a delay. Otherwise, the first one to start executing could consume all available processor resources. These are called "greedy loops."
6. Use integer data types for case structure selector inputs. Floating point values are coerced to integers at the inputs. If the values resulted from calculations, unexpected rounding effects may occur, resulting in the wrong case being selected. In some cases using type defed enums may be even better. The underlying data is integer and the enum item names show up in the case selector labels, helping to document what the case does or why it was selected.
7. Remove the timeout case from the event structure since it never executes. Also avoid Use Default if Unwired on the terminal with your matrix (array) data. You never have a situation where an empty array is appropriate.
Before going any further with the program questions, you need to carefully define your requirements. How many instruments will you have? How many can be active at one time? What kinds of communication between the program and the instruments is required? This includes commands to the instrument, data returned from the instrument, error handling, and timing requirements. What will be done with the data? Display, save to file, use to automatically control another device? What safety requirements or constraints need to be met? Once you have a good requirements document, then you can begin to determine what kind of program architecture is best suited to meet the needs.
I suspect that you may be making some things much more complicated than they need to be while ignoring other important issues.
Lynn

Has anyone multiplexed 5 or more cameras?

Has anyone setup a system using a lot of cameras? I have an application that will require either 5 or 9 cameras. Speed is not a critical factor (the part will not be moving) but I'd like the acquire rate to be on the order of at least a second or two for all 9.
I believe I could use three 1409 cards and synchronize them. Would I have to synchronize all 9 cameras together as well as the cards or if I have 3 hooked up to each, can I just synchronize the 3 cameras hooked to each card and simultaneouly grab from all 3 cards?
Does anyone know of a standalone multiplexer that could take all 9 cameras and output 1 video stream that would go into a 1409 or 1407 or other NI card? I heard of the video multiplexers that will t
ake multiple cameras for recording to a vcr, but I'm not sure one of those would work.
Thanks

I totally agree - using firewire cameras will allow you to hang them all of the same card (only one card required, so you won't need to look at multiplexing anything), will be cheaper, and will allow up to 63 devices on the FireWire bus. As acquisition speed isn't an issue, FireWire would be perfect for your application. This option negates the need for framegrabber cards, although you will need to purchase (not very expensive) the IEEE1394 (FireWire) Vision Toolkit to extend MAX to see your devices, and perform IMAQ functions (more info on the toolkit is here).
You can find more information on IEEE1394 and other vision techniques in my book: Image Acquisition and Processing with LabVIEW.
Copyright © 2004-2015 Christopher G. Relf. Some Rights Reserved. This posting is licensed under a Creative Commons Attribution 2.5 License.

Mux function in labview?

We are working with a LabVIEW VI, and we were wondering if there are any buttons or sub VI's that have multiplexer functionality. We want to put 4 buttons in our front panel, and when one is pressed, we want to choose the set of actions associated with only that button press. Any help is appreciated. Thanks.
Ray

Lets not forget about the radio buttons.
They are nice because they handle the mutual exclusivity and are a enum just waiting to be wired to to a case structure.
Ben
BTW: they can be customized to look like any type of boolean you want.
Message Edited by Ben on 11-30-2006 03:00 PM
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction
Attachments:
RadioButtons.JPG ‏48 KB

How to interface multiple NTC Thermistors to a 8-1 multiplexer and then to myRIO .

I need to measure the temperature of 8 lithium ion battery cells in series individually for my battery management system . So I need to see how can I interface the 8 thermistors with 8 to 1 multiplexer and output to myRIO analog input.

Hey Bakry77,
To expand on what Jeff said you can use an analog multiplexer like this one:
http://www.digikey.com/product-detail/en/HEF4051BP,652/568-1689-5-ND/763293
http://www.nxp.com/documents/data_sheet/HEF4051B.pdf
The 8 thermistors will need to be connected to Y0-Y7 and the myRIO analog input to Z. Then you can use 3 digital outputs from myRIO connected to S1-S3 to select the channel (Y) to pass through (Z).
Let us know if you have more questions about this. I'd love to see the code and your system when you get it working.
Thanks!
-Sam K
LabVIEW Hacker
Join / Follow the LabVIEW Hacker Group on google+

Using third party Strain Amplfiers, feeding DC output to NI 1102 multiplexer to increase channel count, has anyone a vi. already?

As I see required events, measure un-strained millivolt value, file, after applying force, measure strained millivolt value, determine difference between strained and unstrained, convert delta millivolts to strain, and present.
Using NI strain gage boards is good, if we already had them. They are either 4 or 8 chan/board. Amplifiers we already have along with several NI 1102 multiplexed boards. These allow us 32 strains/board.
Calibration can be done by using external shunt with calculated equivalent strain, setting amplifier gain accordingly i.e., 1000ue=1.0 volts.
Can eventually arrive at working vi., but if someone has done this and
are willing to share, it would be of great benifit. Time is always of the essence.

Hello,
Have you taken a look at the Convert Strain Gauge Reading VI that ships with LabVIEW? You could still use an amplifier and then divide the input voltage by the gain and then feed the output to this conversion VI. The VI can be found by searching you functions palette for the word �strain�.
Just let us know if this will help out!
-Justin T.
National Instruments
Also, you can change the type of this VI by right clicking and selecting Select Type.

Problem in creating DLL for a LabVIEW VI

Hi
I am facing problems in creating DLL for a LabVIEW VI. Previously i had no problems in creating DLL for the VI that transmits a message from serial port to NI - PXI 7831-R Reconfigurable I/O card (configured by FPGA MOdule). When i try the same VI with a customized port developed using IVI drivers i am not able to create the DLL. It gives me error as follows:
Fatal Internal error: "datamgr.cpp", Line No: 1882
Please somebody help me out to fix this error.
Regards,
Subramania Bharathi

Hi,
Thanks for your curiosity in replying my questions. I am really sorry for replying so late. Actually the problem was with the NI SWITCH 2503 functions. Actually i was multiplexing the channels of my customized serial port using NI Switch module. This switching is done before i start my communication. My VI follows a sequence as follows.
1. Connect two channelss using Switch functions
2. configuration of both FPGA and the customized port
3. Transmit data from the port
4. Receive it in FPGA.
5. Reset the channels using Switch functions
I never expected that the error was because of NI Switch. When i removed them from my VI i was able to create the DLL and able to create sequence successfully to run in the Testsand. And
further i am using Switch Executive for swithcing the channels in TestStand.
But now i am very curious why it posted me that error when i used my NI Switch function?? I tried to create DLL for a VI that switches two channels and i was successful. But the error occurs only when i combine i with my FPGA functions!! If you could trace out the reason, please let me know
Once again thanks a lot for your support
Regards,
Subramania Bharathi

RS232 De-multiplexing data using Visa Read

Hello
I'm trying to do a simple task, but being new to this I'm having problems.
I transmit data down a RS232 line at 9600 baud. I have two channel of data say x and y where A and B are one byte each.
I multiplex/alternate them down the line i.e ABABABABABAB.....etc
At the labview end I want to seperate the data back to seperate channels for plotting on a graph. i.e A with time and B with time.
There must be a way of toggling some array builder conected to the visa Read VI ie odd for A and even for B and then plotting them in two seperate wave charts.
Iv'e got a single channel working but A and B are mixed together. (see attachment).
Any ideas if it can be done.
Thanks Bill
Attachments:
RS232-single.gif ‏15 KB

RatHunter wrote:
> Hello
>  
> I'm trying to do a simple task, but being new to this I'm having problems.
>  
> I transmit data down a RS232 line at 9600 baud. I have two channel of data say x and y where A and B are one byte each.
> I multiplex/alternate them down the line i.e ABABABABABAB.....etc
>  
> At the labview end I want to seperate the data back to seperate channels for plotting on a graph. i.e A with time and B with time.
>  
> There must be a way of toggling some array builder conected to the visa Read VI ie odd for A and even for B and then plotting them in two seperate wave charts.
>  
> Iv'e got a single channel working but A and B are mixed together. (see attachment).
>  
> Any ideas if it can be done.
>  
> Thanks Bill
>
Hi Bill
I think you were 90% of the way there.
If all you want to do is see the two waveforms on diffierent plots you
can right click on your chart and select stacked plots. I think you
have to increase the size of your ledgend to show two plots.
If you want the data on two different charts, index your array to two
different charts. I'm assuming by your picture that you are reading 2
bytes at a time.
Using two graphs could be useful if your plots had different time
scales. But i think the stacked plots makes more sense.
Good Luck
Eric

My NI-6031E card acts as if the multiplexer is stuck.

Dear Folks,
My NI-6031E 64 channel card acts as if the multiplexer is sticking. I see the same voltages on little groups of 2-3 channels. All the channels are connected to inputs, and there are no overvoltages. The output impedence of the sources should be low, because its the output of an op amp from some optical sensor boxes we build in-house. So all the things listed in the knowledgebase as possible causes are eliminated. I even tried replacing the cable, based on a suggestion from someone on info-labview, but that had no effect. I also ran the on-line E-series diagnostic and all checked out fine.
Now here is the kicker. These same exact systems, same sensor hardware, same cards, have run for the last 5 years in Macs with never a sign of this problem. Now we decide to migrate to PC's running WinXP, and we run into this very large snag. Any helpful ideas out there?
Thanks,
Alvin.

AWMoore,
I have an idea about what might be happening.
When you swtiched from Mac machines to PC machines, you changed the DAQ
driver. If you currently are using NIDAQmx 7.5, your
interchannel delay will be set to a minimum value. In previous
versions of the DAQ driver the interchannel delay was set to round
robin by default which meant the interchannel delay was always the
maximum value. The decrease in interchannel delay might not be
giving your channels enough settling time and thus causing your problem.
There are a few easy ways to test this
1. Change the interchannel delay (convert clock rate) using property nodes, so that it is longer.
2. Remove every other sensor and short the input to the DAQ card it was using (the problem should go away).
To calrify, interchannel delay is the amount of time between each channel's sample.
For example (I am pretty sure you know what interchannel delay is, but
this is for other people who might be reading the posting.):
If you are using 10 analog inputs and are sampling at 10 Hz, a
sample from each channel will be taken every 100 ms. Since the
channels are multiplexed to the same ADC, the samples cannot be taken
at the exact same time. So, we have to take 10 samples one after
another within the 100 ms. In the past we would spread the 10
samples out across the entire 100 ms. This would result in a
sample taken from a channel every 10 ms. Now, we take the samples
as fast as possible. This means that at the beginning of the 100
ms period we take 10 samples with a delay of something like 5 us
between each channel. After the 10 samples are taken (this would
take 5 us times 10 samples = 50 us) the DAQ board does nothing for the
rest of the 100 ms period (99.95 ms would be left over) and then would
repleat the process for the next 100 ms period.
The new setup for the interchannel delay means there is less tolerance
for a sensor's impeadance, but it also means that the samples are taken
at much closer to the same time as one another. Like I said
above, this is just the default setting and it can be changed within
LabVIEW using property nodes (DAQmx Timing Property Node: more->AI
Convert->Rate).
This is just a shot in the dark, but it was what came to my mind
as a possible cause for your problem. I realize you said your
sensors are low impeadance, but they may not be low enough. It is
worth a try.
Lorne Hengst
Application Engineer
National Instruments

Multiplexer in LabVIEW 8.0

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