Compare two analog signals.

How do I compare an analog signal to another analog signal to see which signal has a higher value? I want to display the result on the front panel using an LED indicator.
Solved!
Go to Solution.

Sorry about the lack of inforomation.
I have photodiode voltage four output signals go into the SCC-68 module. The SCC-68 module is hooked up to the PCI 6224 M DAQ Card.
The signals have almost no noise to them, and I am trying to compare the value (voltage) of two analog inputs to see which value is higher. I want to compare the analog inputs of QPD 1.1 & QPD 1.2 from the VI below.
Attachments:
QPD.vi ‏158 KB

Similar Messages

How to make a synchronous acquisition of two analog signals with a one channel DAQ ?

Hi !
It is the first time I use Labview. I have just made some easy VIs, and now, I do not know how to deal with my problem...
My problem : I have only one acquisition card (DAQ Ni 6034E) and I would like
to acquire simultaneously two analog signals. It seems to be possible, in a quasi-synchronous acquisition if the card acquires one point of the first signal, then the first point of the second signal, then the second of the first signal, and so on ... I thougth that I could made two sequencies with a VI of data acquisition in each sequency, with the AI MULT PT. But with this, I think that I will lose the precision of the sampling frequency. And I have to know the sampling fre
quency ...
Thanks for your help !
Carline

Hi Carline,
A PCI-6034E is a low-cost board, which only has one Analog to Digital Converter (ADC).
With only one ADC you can't acquire different channels at the same time. That's why you find a multiplexer before the ADC in this type of board. This enables you to acquire multi-channels at the same rate quasi simultaneously. The samples of the different channels will be interleaved as it is explained in the following knowledge base :
- http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/9379ea091c264b7c86256bc90082ca5d?OpenDocument.
With this method, the sampling frequency is the same for all channels. The sampling frequency of one channel is determined with the "scan rate" parameter. There is only a small delay between the samples
of each channels. When you perform an interval scanning acquisition, this delay depends on the "sample rate" that you specify. To have more informations about this terminology, please refer to the following KBs :
- http://digital.ni.com/public.nsf/websearch/4D1435DF82EF494186256D8A006DD6D4?OpenDocument.
- http://digital.ni.com/public.nsf/websearch/4D1435DF82EF494186256D8A006DD6D4?OpenDocument.
To easily perform such a multi-channels analog acquisition, you can use the VI named "AI Acquire Waveforms.vi". You also can use an example provided with LabVIEW. You just have to browse the NI Example Finder in "Harware Input & output >> Traditional NI-DAQ >> General".
Best regards,
Benjamin
National Instruments France

Graphing two analog signals vs. a third with xy plot

I am trying to plot two analog signals on the y
axis vs. an analog signal on the x axis on an xy plot. If anyone knows how to do this or has
an example vi showing it I would appreciate it.

I think the best starting point for you is the XY graph.vi example. You will locate it in examples\general\graphs\gengraph.llb directory. The example that most probably matches your needs is '(X and Y arrays) Multi Plot' graph.
Hope it helps
Roberto
Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

How to send out two analog signals

hi
I'm running Labview 10.0 with a PXI controller 8196 with with an M-series DAQ board 6289 which has 4 analog out ports. What I have done is create a statemachine which controls a multi LED board (57 LEDs arranged in 7 concentric circles, with a centre LED). The state machine moves between various states such as Fixation point on, Fixation point off, Target on, Target off. At the moment I have one Analog out port which outputs a voltage to tell me which state I am in, but I want to know how to configure a second port to say which LED I am turning on. I am controlling the LED with the digital out, and converting a binary to a digital code so I was just going to convert that digital code (by diving it by some factor) and write out that factor to a second port. I've read I can not confiure two Analog out ports on the same board, but instead I have to cluster the outputs together, I'm just not sure now to do that. I've attached my main vi as well as the two subvi's that the main vi calls. I've looked at some of the other threads and the suggestion was to close one port to open the other, that's just not possible in my case as I need to keep both channels open throughout the whole program as the analog out is constantly changing. I'm also recording from up to 25 analog channels at the same time.
Thanks in advance
NB. I could only add two of the sub vi's that the main program calls, so the main vi will not work, so if need be I can post the other sub vi in an additional post.
Attachments:
VisDisplay_v1.vi ‏121 KB
Build Table_v3.vi ‏45 KB
LEDon.vi ‏24 KB

Hi
For one of the channels it is a stepping voltage which changes between +/- 5 volts depending of which state of the statemachine the program is in, so it is not just a constant voltage through out the whole task. On the second channel I want to out put a single voltage that would signify which LED is turning on, that would just be a constant voltage, but it would not be the same voltage on both channels. I'm just about to try something else and hopefully that will work.
Thanks
Sam

How to use DAQ Assistant to display two analog channels in a XY Graph

Hi,
I am new to LabVIEW. I have been assigned a project in which i have to display two analog signals from an analog potentiostat i.e. voltage and current (also a voltage signal) on a graph using labview. I am using a myDAQ device to acquire these analog signals and I am using labview 2013 to display these signals on a graph. I am using DAQ assistant to configure these signals. Rightnow I have separate graphs for each channel. However, I want a single XY graph to display one voltage as a function of the other i.e. I want to have voltage on the X-axis and current output on the Y axis. Any kind of help is greatly appreciated.
I have attached a screenshot of the VI. that I have made.
Regards,
Max
Attachments:
New Microsoft Word Document (2).docx ‏32 KB

Thanks for the quick response. I was able to make a X-Y graph. However, I can only see a dot floating around. It's not drawing anything. I want to see it making a plot as it collects data. Also, I want to see the complete waveform formed when I stop the VI.
Thanks,
Max

Why i not has two analog outputs at same time ?

Hi, i am try to output two analog signal, which is trangle and sine waveform, with my pci 6036E. i code with Labview 7.1 and the vi is in single loop with both triangle and sine wave analog output to AO0 and AO1.
someguy can help me to figure out is there any problem in my vi or is there any other way.
thank you very much in advance.
scott

Hi All-
Dennis is exactly correct- only a single analog output (or input) task may be run at once on any DAQ board. To add one small bit of advice, CUHK, you will also need to choose the correct polymorphic instance of DAQmx Write to reflect "N Chan N Samples" as shown here:
You will also need to build an array of waveforms using the Build Array function. Hopefully this helps-
Message Edited by Tom W. on 10-17-2005 01:08 PM
Tom W
National Instruments
Attachments:
nchan_nsamp.JPG ‏25 KB

Problem in camparing two sound signals

Gud Afternoon All,
I am trying to compare two sound signals in LabVIEW 2013, but facing some problem. My aim is to detect a particular sound say "Clap Sound". I have recorded that sound and added it into LabVIEW. the other signal is generated by using microphone. I am trying to compare both the recorded signal and generated signal, but unable to find any solution.
any help will be greatly appreciated.
Thank you
Akshay Joshi

I am posting some of my results also.
the waveform named as "Signal" shows two waveform one is the recorded sample(brown) and other one is the sound generated (Orange). there are some moments when the comparision result comes true even when both the waveform overlaps each other. no able to understand the problem.
any help please.
Akshay
Attachments:
result 1.png ‏126 KB
result 2.png ‏128 KB
result 3.png ‏128 KB

Error 200560 while generating two AO signal

Hello,
I am trying to send two Analog signals out and I keep getting the error 200560 at 'wait until done' vi.
I was wondering if there is any solutions to fix this problem.
btw the vi is attached.
Thanks,
Pooya
Solved!
Go to Solution.
Attachments:
2AOsignal.vi ‏27 KB

No problem. A kudo would be nice if you feel I deserve it

Convert analog signals into I2C

hi all,
I am using NI-6351 DAQ unit.I want to capture two analog signal and I2S data from the hardware.
Is it possible to do this?

Depends upon what computer you have. You'll need a player with an output line of some sort, then a converter to go from analog to digital (e.g. http://store.griffintechnology.com/catalogsearch/result/?q=imic). then recording software (free Audacity). Time.
Those are the basics. For higher quality you might want a soundcard that has RCA input and various software packages for cleaning up the audio.
How may cassettes? it may be cheaper to just buy the CD. There are also commercial services that will transfer cassettes. If you're just talking one or two I would go that route because you can spend a lot of time doing this and that will increase sharply if you haven't done this kind of thing before.

How to generate two different analog signal in two different VIs

I'm using a PCIe-6321 board and a SCB-68 connector block. As it has two analog output I would like to use one of these output in one Vi to generate a square waveform and the other output in another VI to generate a sine waveform. Each VI work perfectly separatly but if I run one then the other, the second one doesn't send any signal. Since I don't want to merge the two VIs (It's more convenient to operate them separatly), how can I figure out to make them work together (sometimes).
Solved!
Go to Solution.

I assume you get error -50103 (resource is reserved) at either on vi.
It's not possible to run two AO channels independetly from each other with different VIs since both Tasks are trying to request the same timing engine at the DAQ device.
Christian

How to compare two signals

I would like to compare two singals from NI-DAQ (ch0) and NI-Function generator (ch1).
One(ch0) is 500 Hz and the other(ch1) is a little bit complex (sine and then square pulse 250 times faster than 500Hz).
In so many times, I tried to get a trigger mode in ch0 or ch1.
The comparison points of two signals are starting and ending point(phase) to check the synchronization.
Is it possible to compare them by oscilloscope?
Is there a suitable instrument to compare them conveniently?
Best,
labmaster.

Hello labmaster,
Could you tell me a little more about what you are trying to do? What devices are you using to generate your signals, and where are you trying to start and stop the aquisition? The way you would go about triggering on a 3rd party oscilloscpe will depend on the triggering options supported by that scope.
If a pure hardware-defined oscilloscope does not give you the kind of triggering you need, you might consider looking into using a NI digitizer. Not only do our digitzers support a large variety of triggering methods, you will be able to choose which samples to display through use of LabVIEW.
-Abram

How can I measure the frequencies of two analog input signals simultaneously?

Hi
I have two AI signals, and I need to determine the frequencies of those signals. The frequencies range from 1-125Hz. I currently have a VI where I can sample one of the signals for 1 second (sampling at 300 Hz for 300 samples) and determine the frequency.
I need to read two signals at the same time and get both of the frequencies at the same time, but I can only figure out how to read them individually, so I can read one signal, then one second later I read the second one, then I read the first one again, then the sceond one, etc.. How can I read two signals simultaneously?
Thanks
Attachments:
FreqMeas11.vi ‏41 KB
FreqMeas11.PNG ‏18 KB

"at same time", this depends on the hardware, you can do as has been previously stated just set up a 2 channel acquisition and you will get 2 sampled waveforms back. Most hardware A/D as multiplexed and true simultaneous sampling is not done. At 125Hz this is not an issue unless you are interested in very small phase changes between the samples. just keep this in mind if you are expecting samples to be completly synchronized.
Paul
Paul Falkenstein
Coleman Technologies Inc.
CLA, CPI, AIA-Vision
Labview 4.0- 2013, RT, Vision, FPGA

SB X-FI Titanium.. Digital output works but Analog Signal M.I.A.

@SB X-FI Titanium.. Digital output works but Analog Signal M. I.A. Hi Guys,
I recently installed a new hard dri've on my machine after my power supply failed and fried it. After reinstaling Vista 64 and my drivers I noticed that my sound card was not working properly.
In.. control pannel > Sound > Playback I see my soundblaster listed but only the digital out is showing. There are two other icons listed.. one is for "Digital Output Device 2-High Definition Audio Device.. and one for a 3-High Definition Audio Device. I don't remember these being listed when my sound card was working properly before the HD crash.
No icon representing my analog output (Left/Right, Center, and Rear?Speakers)?is displayed. I reinstalled the drivers, updated the drivers, reformatted my HD and started all over again but nothing works.
I made sure that my motherboard sound card is disabled.. I am really stumped.. The sound card used to work quite well.. Has anyone else had this problem and been able to fix it's
Here is my system info:
Motherboard: Gigabyte GA-MA790FXT-UD5P (Realtek Audio Disabled)
Sound Card: Internal Sound Blaster X-FI Titanium
Any advice is much appreciated.

DRe: SB X-FI Titanium.. Digital output works but Analog Signal M. I.A. High definition audio device is what your card is detected as until you install the original CD driver or the Daniel K 2.0 support pack. Then you can update to the newest Creative drivers. I tried to format just like you and thought that I would just download Creative's newest driver and start from there. No Go!!? The newest Creative driver seems to install, but then after reboot like you, I have multimedia audio device.
So take out your CD if you have it, and run the driver setup only. Then using just this driver you can install all of the newer Creative updates. The Creative auto updater is installed along with your original driver and you will see it detect all available updates.
Easiest solution of all,
Try this pack and save yourself a load of hassle........
http://forums.creative.com/t5/Sound-Blaster/SB-X-Fi-Series-Support-Pack-2-0-05-5-2009/td-p/527485
This will install a very proper Creative driver, and applications that will work very very well on your system compared to the CD orignals

How to acquire analog signal and send a TTL pulse at the same time based on PXI 6123

Hi,
I am using a PXI-6123 data acquisition card, as the picture show in the attachment ,I want to acquire the analog signal of ai0 through reference analog window and at the same time send a TTL signal to trigger my camera. I have tried two methods, one is using the DAQmx Export signal.vi another is using DAQmx connect terminals, but when the data acquisition card acquire the analog signal, the DAQmx Export signal.vi and the DAQmx connect terminals sometime can send an TTL pulse ,sometime can not.
I don’t know why? or some other method that can achieve my arm is appreciated.
Regards
chunlei
Attachments:
method export signal.vi ‏21 KB
method connect terminal.vi ‏36 KB
Send a TTL pulse.JPG ‏288 KB

Hi,
Have things changed over the years?
I need to syncronise a digital output (Modul NI9474) and an analoge input (AI-Modul NI9203) module. I need to measure time intervals from a flank in signal A to a flank in signal B. I would like accuracies of the order of 1 ms. Currently, the signals are not synchronised, with errors of the order of 2 times the block length (block size x sample rate), sometimes much higher. The best I got so far was a block size of around 20 with a sample rate of 1 kHz.
If I use the master and slave settings on the RTSL settings, my program doesn't run properly.
If I use digital signals for input and output, I can syncronise them with RTSL settings and everything is good, but I can't always do that.
Also, if I do anything in the GUI (such as scrollowing something or going to another window), my output gets screwed up properly.
1. What can be done to synchronise AI with DO?
2. Is there something that can be done to avoid messing up the output when something happens in the user interface? (I know that I am messing up the outputs as they make some valves switch and that is loud).
Thanks in advance!

Analog Signal to Digital a Primer

Many users have analog material sitting around, and they would like to get it into digital form, so that it can be edited. As this material is below SD (Standard Definition) quality, I will address the methods for digitizing it, so that it can be best edited in a DV Project. The output can be a DVD-Video, or other format, depending on what one wishes.
The process of getting this analog material into a digital form, is referred to as Capturing, and it is digitizing the analog material and writing it to a file, that can be edited.
One will need some method of getting the analog signals into digital form, and for connecting the analog output from their analog playback device to the computer. Though the analog signal could come from all sorts of devices, I’ll use a VHS tape deck in this example.
Since a VHS tape deck does not have an A-D (Analog to Digital) processor, and also does not have a a digital signal Out, one needs something in between it, and the computer. That “something” serves two needs: mechanical connection of cables and the ability to convert the analog to digital for use in an NLE (Non Linear Editor). That “something” can be a digital video camera with pass-through capabilities, a device, called a “bridge,” or a capture card inserted into a bus slot in the computer. All three have pluses and minuses.
The first two methods rely on one having a FireWire connection on the computer and will use the Capture module in the NLE software.
The digital video camera route is good, as one already owns it. Having one with pass-through capabilities is getting more difficult. The camera also has to have FireWire (FW, IEEE-1394a, or iLink) output, and the computer must have a matching connection.
An A-D bridge will do the same thing: allow one to connect the analog cables to one end/side, process the analog signals to digital and then output via FW to the computer. There are various such bridges available and two of the most often recommended makes/models are: the ADS-Pryo, and theCanopus/Grass Valley ADVC-110. Products, like the Dazzle lineup, just do not seem to work, or work well. I would avoid such.
A dedicated capture card performs the same task, with one exception. The card will mount into an empty PCI slot on the MoBo, and have inputs for the analog cables. The card will have chips on it, to digitize the analog signals and feed these to the computer via the PCI slot. These do not connect via FW, but have one drawback: they must, in virtually every instance, use additional software to do the actual Capture, as most NLE’s cannot directly see and work with them. Some of the included software Capture programs are better, than others. One common issue with many of these cards is a loss of sync, between the Audio and the Video. This is usually static OOS (Out Of Sync), in that it is usually off by a fixed number of frames, and does not drift over time. This can be fixed in the NLE, but is extra work. This ARTICLE will give you tips on correcting OOS.
Now, we are ready to begin the Capture, as our equipment and cables are all ready to go. We have a big decision in front of us - what format/CODEC do we use to Capture our digital files? Since we are doing an SD Project with non-HD (High Def) material, there is one fine choice: DV-AVI Type II w/ 48KHz 16-bit PCM/WAV Audio, using the DV/DVC CODEC. These files will be approximately 13GB / hour of Duration. Storage will need to be considered. These files are also I-frame, meaning that each “Frame” is rendered and available, so that frame-accurate editing is possible. The NLE will not need to do any processing, or conversion of these files, as even the Audio is ready for DVD-Video. Note: there will still be Conforming and the generation of PEK (Waveform Display) files, but the NLE will be able to do this quickly and efficiently.
Using AVI Uncompressed will get you nothing that you can see, other than larger files. Do NOT use any compressed format/CODEC, like MPEG-2, WMV, MOV, etc., as these will loose data from an already inferior source, and will then need conversion to be used, either with a stand-alone conversion program, or internally by the NLE. You loose quality and then have more work to be done. Do not let the temptation of smaller files lure you into using anything but DV-AVI Type II, and just accommodate the larger file sizes.
With the file format/CODEC decision made, the cables and devices hooked up, we’re ready to start the Capture. The exact operation will depend on what our equipment choice has been. See above for talk about additional Capture software, if one uses a capture card. Otherwise, we should be able to use the Capture module of our NLE. The first issue is that we will NOT have Device Control, as we would with a Capture from a miniDV tape-based digital camera, where we can control the mechanical aspects of the camera, during this process. As our VHS deck is hooked up to the A-D bridge, or digital camera w/ pass-through, via analog cables, our control signals cannot be sent to it. One would cue up the tape in the VHS deck, and then choose Record/Capture in the NLE’s Capture module, starting the Capture. Instantly, they would hit Play on the VHS deck, or via that deck’s remote control. This is easier the second time that one does it. I sit with the mouse in my right hand, poised over the Record/Capture button, and the VHS deck’s remote in my left hand, finger hovering over Play. It’s then a 1 - 2 push, and all starts. One can stop the Capture, if an unwanted section of tape comes up. The Capture module of the NLE will direct us on how to proceed from there, should more Captures be wanted. Some will just start up at a later point, and write an additional file for that portion of the tape, but some might require that one basically sets up a new Capture session One should investigate just what their NLE will require for doing multiple Capture sessions from one VHS tape.
When done, one closes the Capture module, and then navigates to the location that these DV-AVI Type II files have been stored in, and Imports them into the Project. This differs slightly from doing the Capture from a miniDV tape camera, as those Captured files are already in the Project.
Edit away, and Export/Share to the necessary output settings, file type and CODEC.
What about those VHS - DVD decks, the ones that will burn a DVD directly from the VHS tape? They seem so simple to use, and for the most part are. However, those DVD-Video discs, contain pretty heavily-compressed MPEG-2 AV streams. These MPEG-2's, besides being compressed, are in aGOP structure and are muxed (Multiplexed into one file with both a Video & Audio stream), plus there is often some Menus and navigation in the first VOB, the main container components of a DVD-Video. Many NLE’s can Import the VOB’s, and basically rip the MPEG-2 out of them, but that first VOB can be highly problematic, due to the way that most of those decks do the Menus and navigation. It is seldom 100% DVD-compliant by the DVD-specs. This can be a major problem. This ARTICLE will give you some background and tips on DVD VOB's.
Those dual-decks are good for doing one thing, regarding the DVD’s that they produce - provide one with an archival DVD-Video of the VHS tape, and not to be edited. However, the VHS side of these works well with an A-D bridge, just like a pure VHS deck does. I would strongly recommend that one does NOT use the DVD-Video portion of these, if editing will be desired. They cause many more problems, than they solve - just use them for an “archive” copy of the tape to a DVD-Video, for playback on a computer via DVD software or a set-top player, hooked to a TV.
What about film? Well, film is obviously analog, and one needs to digitize this to edit on the computer. The process of this digitizing is referred to as telecineing the film. While one can buy equipment to do this, it is expensive, and involves a lot of setup and testing to get the job done. There are many service bureaus, that offer telecining. Some are better than others. The main considerations are: care in handling of fragile film, how the telecining is done, i.e. frame by frame w/ a liquid gate, or just by straight projection, and then output format for the digitized files. Some of these services will offer a DVD-Video disc. Do not be tempted to do this. See above. Others will offer to write these digitized files to a miniDV tape, and this is just fine. One does then need a miniDV camera, or miniDV tape deck, to then do the Capture from, but the quality and editability will be preserved. The final delivery format would be to put these DV-AVI Type II files onto an external HDD. This saves one from having to do the Capture from miniDV tape, having to have a miniDV camera, or miniDV deck, and only Importing of those files would be required to get them into the Project. Many of these service bureaus will either sell you the external, or use one provided to them. Check out specifications for things like format of the external. FAT-32 will limit the file sizes to ~ 4GB max, and NTSF will have no such limitations. However, if the service bureau is on Mac, and you’re on the PC, their Mac’s can ONLY see FAT-32 HDD’s. Talk this over with the service bureau first, so that there are no surprises later on.
Hope that this helps,
Hunt
PS - also see this FAQ Entry for more detail.

the_wine_snob wrote:
Products, like the Dazzle lineup, just do not seem to work, or work well. I would avoid such.
Although I now have a Canopus ADVC300 I previously used a Magix 'Movies on DVD' USB device. I found the results from this to be particularly good and, to my ageing eyes, I see very little quality difference.
I think this is because Magix use their proprietary high quality codec (from their Pro products) to capture the footage. Like DV-AVI it runs around 10GB+ per hour. This can then, very simply, be exported to DV-AVI Type 2 for use in PRE. Note that there are some sound synchronisation issues with the 'out of the box' settings - but the fix is quick and I posted details to the Magix forum.
Would I revert if I could return my ADVC300 bridge? Probably not - the firewire connection and the PC seeing the box as a camcorder adds to ease of use. In fact I am pleased to have both. There are some things Magix does better than PRE7 (batch exporting each scene as an individual DV-AVI file being just one) and it has smart-rendering which is handy for quick clip splitting/exporting.
Cheers,
Neale
Insanity is hereditary, you get it from your children

Compare two analog signals.

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