Unclearity about analog signals

Greetings,
I am trying to create a small DAQ system that digitalizes a analog signal and displays the waveform and spectral analysis. I know that the analog waveform component receives and array to plot the waveform. However I am having doubts about how many samples I need to collect to create the exact graphs that is annexed to this post.
Could anyone give me some help please?
Thanks
Attachments:
InverterWaveform.PNG ‏8 KB
SpectralInverter.PNG ‏8 KB

Recently I tried to made this program to aquire the analog data from a serial port based device. I am trying to use the waveform graph from the right in my program instead of the graph from the left.
I do know that I need to create an array to store the aquired elements and connect to the wave form graph.
Question is: What is the correct way to program that?
My serial device is programmed to receive an character and return a 0-255 number that corresponds to the aquired value.
Message Edited by Borges on 05-13-2009 02:31 PM
Attachments:
sample1.PNG ‏31 KB
sample2.PNG ‏28 KB

Similar Messages

Analog signal staircase help

Hello all,
I'm still new to LabVIEW, but I've played around enough to create a simple analog waveform generator. The signals produced appear staircased when displayed on an oscilloscope, but are smooth when I reread the signals into an analog input (as shown by the waveform graph). How can I change my program settings so that I can view this staircased signal?
I run LabVIEW 2010, and use a USB X Series Multifunction DAQ.
Thanks,
-Olivier
Solved!
Go to Solution.
Attachments:
Waveform Generator.vi ‏106 KB

Olivier,
Thank you for posting. I am a little unclear about what some of the front panel controls are in you're images, but I will explain the best that I can about what I believe is going on.
Take a look at the following images.
Generating a 1kHz sine wave:
Acquiring at 100kHz:
Acquiring at the Nyquist Frequency (2X the input signal's frequency):
What I am trying to demonstrate here is that you are only going to see a smooth signal if you are sampling fast enough. For instance, if you generate a 1kHz and sample at 2kHz, you will only see two samples per period. This will give you an accurate period and frequency, but nothing else. Because an analog to digital converter is used here, you must sample at a much faster rate to get a "smooth" signal. In my above 100kHz acquisition, you see that we are getting 100 samples per period which produces a much smoother waveform. I would suggest that you acquire a 5kHz signal at something on the order of 500kHz to see a smooth signal.
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Regards,
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National Instruments

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.
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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.
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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.
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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

How do i send an analog signal to trigger another program

I am trying to send out an analog signal from labView that will start Bioware. How can I do this?

Hi Orbz,
There are 3 Send modes in Logic:
• Pre Fader (original signal is sent before it reaches the channel strip's fader etc.
• Post Fader (sent before volume fader adjustments)
• Post Pan (send before volume fader and Pan/Balance adjustments).
Click and hold on the Send slot in your synth channel strip and select Post Pan fro the drop-down menu.
Funnily enough I've just finished writing a tutorial about this very topic!! It's not published yet, but will appear on the macProVideo.com blog in the coming days...
http://www.macprovideo.com/blog/

Analog signal from PXI

Hi everybody,
I have a problem: I cannot acquire 6 analog signals with a PXIe 8135 with 4MS/s. I use two boards with 4 MS/s, 16 bits and 8 Analog Inputs. I use a subVI of SAMPLE CLOCK for configuration with this parameters, Continuous SIGNAL, SAMPLE RATE = 4MS/s ( see attachment ). With one signal is ok, but with 2 signals, i have an overload Memory Message.
Where is the problem in the VI?
Thanks for your help.
Attachments:
acq_and_graph.zip ‏165 KB
acquire&loggdata.png ‏230 KB

Quickly looking through your code now, try removing the "Number of Samples analog". Since you are using Continuous Samples, you are just limiting the buffer and also limiting how many samples you can read at a time.
But you might want to think about using Finite Samples. You know how long you want to log for and you know your sample rate. So why not just do the simple math and tell DAQmx to get that many samples? You can use the DAQmx Task Done? VI to see if it is done. That would be much simpler than checking the time that has elapsed.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

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

Msg about no signal, no bars, then poof full signal all in 3-5sec

So, I've had my iphone for about two weeks. In that two weeks I've been using my phone when a pop up message comes up saying (next time I'm going to write it down) something about not being able to connect to the network (and there are 0 bars). I click ok, and then immediately after the phone gets full signal again and works like a champ.
The last time it happened was yesterday and it was while I was looking at an app store review for something.
I did some searching, saw a lot of "signal" posts, but without digging through pages I didn't see a similar post. Is this a hardware or just local network issue? Stopped by the ATT store on my way home and asked (with little expectation) and of course was told by the guy that helped me that he'd never heard of such a thing, and that I should just reboot the phone and it should be ok.
Any help would be greatly appreciated
Thanks,

OP, there's hundreds of posts in this forum that just don't get it, a sad read about blathering about poor signals and all that. Apple and ATT are telling users to turn off 3G on the iPhones (the only ATT-branded phone available today that disables WCDMA without a hack or SEEM-edit; if you don't know what SEEMs are, that's a whole different read).
First, the bars on the 3G network aren't "signal" - it's a representation/ratio of power available to the CDMA/WCDMA device compared to the noise on the network - Ec/No. Apple changed the "bars" from the originally-mapped RSSI (wrong) to Ec/No (correct) - I posted about this months ago.
For ATT, every WCDMA device on a network - the boxes on the towers _and every single 3G cell phone_ generates noise - and the system has to be balanced to work properly. Resets are acceptable. Verizon's completely controlled device deployment (I have a VZW PDA to go with the iPhone) keeps conflicts to a minimum and their system power balanced. Each cell phone is a potential disruptive force within a network - and most of the posters in this forum don't get that; read the analogy at the bottom of this wiki:
http://en.wikipedia.org/wiki/Near-far_problem
Your iPhone, moving from place to place, is a potential source of disruption to other ATTWS 3G devices. When you move from near a window in your house to the basement with your phone in your pocket, you're changing the power balance of the network around you and the ATTWS phones in your area - if a bus with 10 ATTWS subscribers drives by your house, that temporarily disrupts your connection to the network. If a couple of people down the street use unlocked 3G phones from across the pond that aren't set up to work well with the ATT 3G network, you'll all have less-than-stellar service - VZW controls all of their phones and the software on those devices; I've had two dropped calls on my VZW PDA since February and none on my V325 in over two years, in part due to VZW's vast experience with CDMA networks.
ATTWS is new to the CDMA networking thing, and they don't control the types of phones on their network - I know guys with E71s, unlocked 3G RAZRs direct from MOTO, O2 and Telstra phones in my neighborhood, and I've got a wireless broadband card, and we live near three major roads carrying tens of thousands of cars and hundreds of full buses everyday - a networking nightmare for ATTWS with unlicensed devices competing for data and voice capacity.
Wipe your iPhone, start with a fresh firmware and install your apps, install apps from your PC/Mac and not via the 3G network, get one of the new ATTWS SIM cards (out for a few weeks now), and don't move around your house/office quite so much - and it wouldn't hurt to get a repeater (ATTWS is currently in closed beta testing of femtocells to help equalize the network loading). VZW tells us that they won't guarantee our phones will work in our houses - they just don't tell us why. The reps in the ATTWS stores are generally clueless - or they'd be working somewhere else - the stores are retail outlets, not tech help centers. BTW, all smartphones and PDAs should be rebooted periodically - don't let anybody tell you differently - the iPhone's got at least six radios stuffed in it and in close proximity to a processor, all in a box that fits in your pocket; XP boxes go wonky if the network goes down, your iPhone or my Treo do the same when they're cut off from the network, and they do sleep from time to time.
Another reason that your "bars" go away - I live near both 1900 and 850 towers; using Test Mode confirmed it for me, and I can see the bars go to zero when my iPhone's likely changing from one network to the other or when it goes to sleep, and my Treo does it to, to conserve battery power or when they get bumped off the network.
Apple's got to work on their software a little more to get the power balancing thing down, but my backup Z9 and my mom's V3xx get bumped off too. It's not just them, it's you too. Don't waste too much time poking around these forums, head over the iPhone and ATTWS forums at HowardForums.com - they've been at it a lot longer and have some posters that really have an idea of what's going on. And, take your iPhone to an Apple Store - they have diagnostic software that can troubleshoot issues and failures; Apple generally doesn't moderate these forums like HoFo, but just edits out bad behavior - at HoFo, the mods chime in and seek to help out.
That's my last post here in these forums, good luck.

Measuring frequencies present in an analog signal

Hello,
I want to measure the frequencies present in an incoming analog pulse signal.
I tried it as shown in the vi using ‘Extract single tone information.vi’ which was showing the value as ‘39m’ I dont understand what is this value. Can someone explain the right way of measuring the frequencies present in the signal so that I can feed them to my bandpass filter limits.
Thanks.
Solved!
Go to Solution.
Attachments:
Measure_Frequency.vi ‏102 KB

Hello,
The acquired analog signal is pretty much filtered as shown in the attached image.
Now I am collecting data for 5 seconds (collecting 2500 samples using collector.vi ) and finding the single tone frequency from it and plotting the measured frequency after 5secs in a waveform chart.
But I am confused with these1)The original detected signal has an amplitude of above 1.6V but the measured amplitude only shows 0.6V and 2) how the waveform chart has a plot plotted over the duration of 5seconds when the frequency is measured for every 5seconds data I mean shouldn’t the chart has a plotted value of HeartRate plotted for every 5 seconds.
Can someone explain a bit about these.
Thanks.
Attachments:
Freq.JPG ‏74 KB
Frequencyplot.vi ‏94 KB

Input analog signal with trig signal on DAQPad6020E

I would like to record an input analog signal in continous with trig signal on falling edge. The frequency trig is 3.87hz (258ms)with 5V level. In fact I want to record the input analog signal every 258ms.
I use a DAQPad6020E and the VIs "AI-Config", "AI-Start" and "AI-Read" with a "digital A" trigger type (PFI0/TRIG1 on block connectors) and record datas in a file.
I use the following configuration:
- sampling rate= 100000 S/s (max rate DAQPad6020E)
- minimum scan= 25200 pts
When I read the datas I notice that the gap between the first point of the first acquisition and the first point of the second acquisition is 1016ms and not 258ms like the trig.
I change the configuration:
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The gap is now 516ms (it correspond to two trig)
An other configuration:
- sampling rate= 155 S/s
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The gap is 516ms (it correspond to two trig)
I use also the VI "AI-Wave" but the results are the same.
I don't understand what happend. Maybe it's due to the card limits ?
Thank you for your answer.

Hello,
A trigger is an external stimulus that initiates one or more instrument functions. Trigger stimuli include a front panel button, an external input voltage pulse, or a bus trigger command. The trigger may also be derived from attributes of the actual signal to be acquired, such as the level and slope of the signal.
A trigger is not a clock.
If you want acquire with a specific clock, I advise you to use external clock. Instead of using your signal as trigger, use it as external clock.
Have a look at "Cont Acq & Graph Ext Scan Clk - D trig.vi" example. This example is provided with LabVIEW (Help >> Example Finder).
Here a tutorial about external clock acquisition :
http://zone.ni.com/devzone/conceptd.nsf/webmain/7d8eaea1d87cfb2686256802007b8c52?OpenDocument
Regards,
Isabelle
Ingénieur d'applications
National Instruments France

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

HELP about analog output video

Hello, I´m need help about analog output video in Premiere CS5 using Matrox RTX2. I need to crop a video with resolution in 1440x1080 to 4:3 in output analog. But what happens is wrong (I think). My video is in format anamorphic and the other option is 16:9 letterbox. Is there any way to crop the video without using effects. Thanks a Lot and sorry my bad english (my native language is Portuguese).

There are no 4:3 HD specifications. You'll have to put the video into a normal SD sequence, and scale it down till the top and bottom of the video meet the frame. That way the sides will be cut off.

How to input/output a digital signal and acquire an analog signal at the same time?

Dasylab, version: 8.0.04
Acquirement Card: PCI1002L
When I use DasyLab to acquire the analog signals is no problem without digital inputs and outputs,
and when I use DasyLab to input or output a digital signal is no problem also, but when I do that at the
same time, DasyLab tell me the rate is too high and stop.
so, I searched the manual book1 (user guide) for that, it showed me :
To internally equalize measurement time and system time in the analog input, digital input and counter
hardware modules, use the following settings:
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   Sampling rate: <= 5Hz
   Block size: =1
the problem is, if I set the Sampling rate to 5Hz, the speed of the acquirement datas is not enough for my
application.
so, how to improve it? who can give me a example programm for me. thanks!
by the way, I come from China, my English isn't good, I'm sorry.
Allen, China.

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!

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!

How do I set a threshold from an analog signal (4-20ma) coming in on a cfp AI 110, to trigger an alarm on my UI?

I have the alarm set, indicator set, just need a digital trigger from an analog input. I realize I could use an external switch into a digital input, but would rather use what we have. We are using this analog signal for other purposes as well. This application is for controlling a machine. Thanks.....

Hi Bob,
The way you have your Case structure setup now is that the “7” case will only get executed if the value from the wire is exactly 7. This same applies to the “8”. Also, there is no default case, so if value does not match any of the cases then your indicator will not change.
You indicated earlier that you need the indicator to be ON when the value is below 7mA and OFF when above 7mA. You will want some like this:
Alternatively could just use the Not function inside the Boolean palette to achieve the same functionality without the case structure.
You will want to check out the LabVIEW Training Page.
Message Edited by DiscoBall on 03-27-2009 12:12 PM
Message Edited by DiscoBall on 03-27-2009 12:13 PM
Joshua B.
National Instruments
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Problem when combinning PWM signal and Analog signal TOGETHER!

Hello everybody,
first of all i have DAQmx 6212, and i need to run a small water pump (9V-16V) which needs to be driven by a PWM signal; also i have a motor (5V-13V) for a water valve that needs to be driven by a analog signal and it has a built in a force feedback potentiometer, i connected on the extremeties of this potentiometer +5V from the DAQmx and used the output voltage from the third extremety as a diagnose value for knowing the position of the motor.
my VI shows:
1. is a normal Counter output to create my PWMout signal.
2. is an analog input i use it as a PWMin to the LabVIEW to diagnose what is happenning in my water pump through the duty cycle and the frequency.
3. is an analog input from the third extremety of the potentiometer.
4. is an analog output which i have used as a power supply for the motor valve and i have used an AC/DC amplifier to aplify the signal from the DAQmx and drive the motor, between (3. and 4.) i have made a feedback with some calculations i had a P-controller to know the actual position of the motor valve.
My Problem:
when putting 1. and 2. in the same VI alone, i am getting a clean PWM in/out with no problems mentioned;
also when putting 3. and 4. in the same VI alone i can control the motor valve without any problems;
but when i put all these 4 together as found in the attached VI, i have a problem that the motor valve is running continously without stopping even if i change the valve position between 0 and 100 %, i should mention that i am seeing a normal PWM out/in signal on my oscilloscope, one other thing that if i delete one of (1. or 2.) and run the VI the motor valve is working fine without any problems.
so this my problem, if you can think of any solution please let me know.
thanks in advance for your help.
Regards,
Alosh
Solved!
Go to Solution.
Attachments:
pwm.out.in.analog.out.in.vi ‏45 KB

Dear nathand thanks for your reply,
i have ran the vi again and i am have error no 50103 from the (AI, number 3. ) but it is not displaying the error message, the VI keeps running without any error notification.
adding to that, i have tested the VI again today by placing (1. and 2.for the PWM inout) together in one VI and (3. and 4.for the motor valve) in another VI and ran them one after the other, i had another problem. if i turn the motor valve vi, the motor will run smoothly but in the pwm vi i will have a problem in which the AI did not read any value. also doing this vice versa by running the pwm vi first it will work perfect but the motor vi will have problem in reading the measured voltage in AI during this the motor will keep on running without stopping.
so i think now the problem is in AI (2. and 3.) readings they are interfering on each other but i am not discovering where is my problem...
Q: does the AI's seems well build or i can do it in an another way so to get over the interfering?
Regards,
Alosh

Unclearity about analog signals

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