Low Amplitude Signal on PXI-4461

I am curently using two PXI's to output an analog signal through LabVIEW 2009 to an oscilloscope:
PXI-4461 is running the attachment (labeled appropriately) below. It also produces the green line on the graph. It appears correct on the oscilloscope.
PXI-5412 is running the other attachment (labeled appropriately) below. It produces the yellow line on the graph. This amplitude is measured correctly (or so it shows in the margin of the picture), however it gives me a "Low Signal Amplitude" warning and displays the wave much smaller than the "correct" version from the 4461.
*Note: I suppose it is possible that the PXI-4461 (green) is wrong and the PXI-5412 (yellow) is right, but since the PXI-5412 (yellow) produces the error, i am lead to believe that it is the problem.
I could use some help figuring out what might be causing this inconsistency and how might I go about remedying this issue.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Solved!
Go to Solution.
Attachments:
PXI-4461 Function Generator.vi ‏87 KB
PXI-5412 Function Generator.vi ‏23 KB

This has nothing to do with LabVIEW. It is all oscilloscope related. The reason the yellow signal is smaller than the green is because your scales are different. Look at the bottom of your oscilloscpe: Ch2 says "500mV per division" while channel 3 says "1V per division". You probably get a "low signal amplitude" because you signal is less than "2 divisions" and the scope sugests you to change this. There should be a button named "Autoscale" on your scope which you can hit if you want.

Similar Messages

Noisy signal when using PXI 4461 DC Voltage

Hi
I'm conducting shot noise measurements on single molecule junctions. In order to bias the sample with a very clean DC bias, we've purchased the NI PXI-4461 for our lab. According to the specifications, the output noise should be in a order of 23*10^-6V for a bandwidth of 80kHz. However, when testing the V output by connecting it to a spectrum analyzer (SR780) at V=0 DC bias and differential output mode (To generate the DC signal, I've simply used the test panels.), the output spectra was very noisy (x units are Hz y units are Vrms/sqrt(Hz)):
So we've discovered the output is actually very noisy and especially has a high peak at ~53kHz, probably from the AC power supply. Connecting a 10Hz low pass filter significantly improved the result:
Which shows that the output noise filters of the 4461 are probably not activated. Also the peak at 50kHz from the power supply still remains very substantial (later, we've managed to reduce it further by disconnecting the ground of the output). According the the specifications of the 4461, it should be possible to get a very clean DC signal from it:
"NI 4461 output channels have both analog and digital anti-imaging filters. These filters remove the unwanted out-of-band components generated when an analog signal is produced from digital data. The digital filters limit the bandwidth of the output signal to half the original conversion rate, thereby rejecting images caused by the 8-times oversampling process. The signals generated by the analog output circuitry are low-distortion, low-noise, flat-frequency analog signals."
So my questions are:
1. How can I make these anti imaging filters work using labview? (code examples will be great)
2. Are there is any other configuration parameters of the PXI-4461 which can be used to lower the output noise?
3. How can I reduce the power supply noise? (regarding this - we also have a computer PXIe-8106 running on the same PXI chassis)
Sincerely,
Ran Vardimon

Hello Ran,
It sounds like your main issue is filtering the output noise from your DSA card and you're trying to find a proprty to activate the anti-aliasing filters. There is a DAQmx channel property node that can filter that noise, and is described in the KnowledgeBase article here. The article covers the AI property, but you can use the class browser to find the AO version as in the attached picture. Hopefully this helps.
Jake H | Applications Engineer | National Instruments
Attachments:
Class Browser.png ‏25 KB

PXI-4461 Onboard device memory underflow

I am using a PXI-4461 to generate an aquire a singal. When i generate the signal i get error -200621( onboard device memory underflow) onDAQmx Stop VI. I donot understand what the error means.
Signal Information
Signal Type=Sine Wave
Frequency=3K
amplitude=0.3V
Sampling Rate=48K
Number of samples sent=48000 or 1sec
I have tried reducing my sample rate to 20000 but that didnot help much. How do i get rid of this error
I have attached an picture of my vi below
Thanks. Any help whould be much appreciated.
CS
Solved!
Go to Solution.
Attachments:
Code Image.png ‏82 KB

Welcome and thank you for using the Discussion Forums! This error is most likely due to the non-regeneration property you have set. What's happening is that LabVIEW generates your two sine waves continuously, but slower than the update rate of the DAQ card, so the buffer gets empty before it can write enough samples to the buffer so that the 4461 can keep generating the voltage values on the channel.
What you could do is simply set the Regeneration mode to "Allow Regeneration". I tried the non-regeneration and regeneration property on the "Voltage - Continuous Output.vi" and it works with regeneration enabled.
Regards,
Daniel REDS
RF Systems Engineer
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PXI-4461 Filter Delay

Hi,
I have some questions about the Filter Delays associated with the PCI or PXI-4461 card.
I do not have this card, but am interested in it, especially the 24-bit analog output function, to control a test apparatus I have. The problem I face now is that the test apparatus and sensors are sensitive enough to see each bit change in the 16-bit resolution analog control voltage I now use to control the apparatus. I like the sensitivity of my equipment, but do not like seeing the bit changes in the control signal in the resulting data.
I am concerned about how the Filter Delays inherent in the 4461 operation, the roughly 3 milli second delays from instructing the 4461 to output (or input) a signal, and that output signal actually responding (as I understand what the Filter Delay is), will affect the ability of that card being effectively used as an instrument control signal. I do not want milli second delays interrupting the otherwise smooth control of the test apparatus. I am interested in learning about what triggers a filter delay so it can be avoided if possible.
For example, I might generate an analog output signal to control my test apparatus that consists of several monotonically increasing linear voltage ramps with different slopes, each voltage ramp slope representing a different sliding velocity for the servo mechanism in my test machine to follow.
I could do this by calculating each ramp separately and join them together to make one lengthy voltage ramp / waveform where voltage changes as a function of time vary within the longer waveform. That longer waveform is fed to the DAC to play back at a constant clock rate. Besides the initial start-up of the DAC, I don’t think that there there would be any filtering delays in that example, would there?
However, I do control the machine on the fly so to speak, where changes in the control voltage ramp occurs at arbitrary times without stopping the program, calculations for each DAC update are done right before it’s sent to the DAC. Would each DAC change in this case trigger a filter delay?
Another option to generate a machine control signal is to generate a simple voltage ramp that starts at -10V and ends at +10V that has 16,777,216 values, one for each of the 24-bits. As the program runs, the clock rate is varied which causes the DAC to generate bit changes at different rates, which varies the rate the voltage output changes with time. Will each chang of the clock rate trigger a filter delay?
I realize that there are other ways to increase the resolution of an analog output using 2 or more 12 and/or 16-bit analog outputs, but they too have their limitations. It would be nice to simply have a high resolution analog DAC without the added external hardware and added programming complications associated with the multi DAC output ‘solutions’.
Any comments regarding the 4461 cards and how they might behave under these scenarios, or suggestions for alternative hardware/software to get a finer DAC output resolution would be appreciated.
thanks,
Brian

Briank:
The filter delay in an analog output is dependent on the sampling rate that you choose. If the 3-4 ms delay is too much for your application, you can sample at a faster rate. For example, if you sample anywhere between 102.4 - 204..8 kS/s, your delay is 32 samples. This corresponds to a delay of 0.1563 to 0.3125 ms. Do these numbers seem more reasonable for your application?
The filter delay happens regardless, it is not triggered. Let's take a filter delay of 1 ms for example. From the time the data is transferred onto the card, there is a 1 ms delay as it propagates through the DAC. There is a constant lag time when using any output channel.
Changing the clock rate during run-time is not supported, the better way to do this would be to sample at the highest rate possible and create an array of data that has multiple samples of the same value to emulate a lower sample rate. This gives you the benefit of having the shortest filter delay time (0.3 ms).
Nathan M.
Applications Engineer
National Instruments

How to measure the directivity of microphone by pxi-4461

i want to measure the directivity of microphone, but how can i do it by pxi-4461 ? i have a standard microphone, an under test microphone and pxi-4461? can you give me some ideas? thanks

ok， follow is my ideas:
1、the fixed source is generated by the port AO0 of 4461
2、the signal via power amplifier to transmitting transducer(device under test),
3、the transmitting transducer is placed on a turntable(0-360°)
4、the signal receive by standard microphone, and access into AI1 of 4461
if the above true, i just need to record the sound level(Sound Level.Vi) in different angle, and polt it by Poalr Plot.vi?
thanks again

PXI 4461 simultaneously read and generate

I am using PXI 4461 card, which has 2 inputs and 2 outputs.
I have a sequence, which will be loaded for multi UUT testing at the same time. I am trying to use AI0, AI1 to read the signals, which are generated by UUTs at the same time. One UUT can measure signal at AI0 and other UUT should measure AI1.
I was in impression that it can be possible to measure both AI0 and AI1 at the same time. But it's giving the error, when I try to measure.
I made the attached VI as an reentrant. Please let me know if this is possible.
I would like to know same if this is possible to generate from AO0, AO1 at the same time with different frequencies (1KHz, 10KHz). AO0 should generate signal with 1KHz and AO1 should generated signal with 10KHz. Is this possible?
Thanks,
Attachments:
4461.vi ‏17 KB

LV2010,
Thank you for using the forums!
First off, I ran your VI as is with one AI. I received the following error:
The message is letting you know you have your MIN set higher than your MAX. Basically, your max value is currently set to -10 and your min value is set to 10. Switch those, and you eliminate the error.
In order to read from both ai0 and ai1, you can simply put them both in the control window:
This is called channel expansion.
In order to see the waveforms, I added a Waveform Graph to my front panel and then on the block diagram I wired it to the data output of the DAQmx read.
The DAQmx Read VI will read the channels in the order in which you specify in the Physical Channels terminal.
In terms of generating two outputs from AO0 and AO1 at the same time, that is definitely something you can do! I have attached the final VI, but this is how I did it...
First, I opened the example finder by going to Help >> Find Examples. On the bottom left, I selected the PXI-4461 and marked the box next to where it says "Limit results to hardware". Navigating to Hardware Input and Output >> DAQmx >> Analog Generation >> Voltage, I opened the example "Cont Gen Voltage Wfm-Int Clk-Non Regeneration.vi".
Taking a look, this will allow us to generate one waveform at one frequency. First off, I know I want to output two different waveforms with separate information. I selected the relevant indicators and controls, then pressed Ctrl+C and dragged it over to create a copy. I changed labels and moved stop button to make it more appealing, and changed the waveform information.
Then, I moved to the block diagram. I placed a new Function Generator.vi and moved/wired the controls/indicators I created above to the inputs/outputs of the new function. I changed the error wire to go through the new Function Generator.vi before going into the DAQmx write. Lastly, I connected the sampling information from the first function generator to the new one.
Next, we need to change the write function. It is currently set up to write an along waveform with 1 channel and N samples. We want N channels and N samples. Change the DAQmx write to Analog >> Multiple Channels >> Multiple Samples >> 1D Waveform. By doing so, it creates an broken wire between the output of the one function generator.vi that is still wired to the input of the DAQmx write vi.
The reason for this is that the DAQmx write with N channels and N samples expects an array of waveforms, not a single waveform. I deleted this wire and placed a Build Array (Programming >> Arrays >> Build Array). I dragged it down to expand it to hold two waveforms, one for ao1 and one for ao0.
The order that you wire the two waveforms into the array will determine which waveform is output on which channel. The first waveform in the array will be output first. We will put the first function generator output to the first row of the Build Array function and the second to the bottom row. Then wire the output of the Build Array function into the DAQmx write.
The block diagram now looks like this:
All that is left is left is to specify what channels we want. We will again use channel expansion. Remember, the first waveform we wired into our array will be the first output, and the first in the list of the control will be the channel output first.
The front panel now looks like this:
And we are done! I have attached the final version of this VI as well as the edited version of the VI you posted.
I know this was long, but I hope it was helpful!
Also, here is an article and here is an example from our community forums you may find helpful.
The attached Code is provided As Is. It has not been tested or validated as a product, for use in a deployed application or system, or for use in hazardous environments. You assume all risks for use of the Code and use of the Code is subject to the Sample Code License Terms which can be found at: http://ni.com/samplecodelicense
Katie
Katie Collette
National Instruments
Attachments:
Edited-Cont Gen Voltage Wfm-Int Clk-Non Regeneration.vi ‏38 KB
Edited 4461.vi ‏22 KB

Error during self calibration - PXI-4461

We are running Calibration Executive 3.2. We are using a PXI chassis and controller and trying to calibrate a PXI-4461 card.
In running the procedure, we received the following error during Self Calibration:
Error 200718 occurred at DAQmx Self Calibration.VI at step self calibrate.
Any guidance in resolving this issue would be appreciated.
Richard

Here is the info from the calibration report. I can email you a PDF of the report and also a screen capture of the error message which states: "Measurement taken during calibration produced an invalid AI gain calibration constant. If performing an external calibration, ensure that the reference voltage passed to the calibration VI or function is correct. Repeat the calibration. If the error persists, conatct National Instruments Technical Support.
CALIBRATION PERFORMANCE TEST DATA
DUT Information
Type: PXI-4461
Tracking Number: 33367
Serial Number: 33367
Notes
Customer Information
Name: Cal Lab
Address:
Purchase Order:
Notes
Environmental Conditions
Temperature: 23.0 C
Humidity: 13.0 %
Operator Information
Operator Name: administrator
Calibration Date: Friday, March 23, 2007
16:27:03
Notes: Error or termination
occurred. This calibration
may not be valid. Error
code: -200718 Error
message: Error -200718
occurred at DAQmx Self
Calibrate.vi at step Self
Calibrate Possible
reason(s): Measurement
taken during calibration
produced an inval
PXI-4461 Serial Number: 33367
Friday, March 23, 2007 16:27:03 Page 1 of 2
Standards used during Calibration
Type Tracking Number Calibration Due Date Notes
Fluke 5500A Multifunction
Calibrator
32261 3/15/2008
DMM 32260 11/21/2007
33250A 29536 10/13/2007
Calibration Results
Test Canceled
Calibration As Found As Left
Test Value Low Limit Reading High Limit PassFail Low Limit Reading High Limit PassFail
N/A N/A N/A N/A N/A N/A N/A N/A N/A
PXI-4461 Serial Number: 33367
Friday, March 23, 2007 16:27:03 Page 2 of 2

PXI-4461 frequency sweep.

Hi,
I'm writing a sweep function for PXI-4461 to measure frequency response. I fixed the number of samples of sine wave as 100 and the sampling frequency is varied by ten times the output frequency. The Input and Output channels clock rates are changed on the fly according to the output frequency. However, I found that the PXI-4461 is needed to stop the task before changing the clock rate, am I right? Therefore, the output signal from 4461 become on and off repeatedly due to the task start/stop. I want the signal generated continuously, any suggestions?
Bill

If you are using LabVIEW, you could try the swept sine in the Sound and Vibration Toolkit. It uses a constant sample rate and update rate and changes the generated frequency on the fly. There are no glitches in the output.
Doug
NI Sound and Vibration

Has anyone performed a correlation study between a PXI-4461(or PCI) vs the Audio Precision 2722?

Hello,
Wondering how you would configure the input and output connections on the 4461 (psuedo/differential) and correlate that to the 2722 (balanced/unbalanced, floating, etc).
I'm mostly interested in comparing voltage levels.
Thank you in advance

Hello dmf,
I am by no means an expert on pro-audio equipment, but I can tell you about the PXI-4461. First off for a description of pseudo differential inputs you can look at this KnolwedgeBase article: What Is a Pseudodifferential Input?
As my understanding of balanced inputs goes, these signals consist of two signal wires and a ground reference. The signals lines carry the same signals, but one line is inverted (180 degree phase shift). This is useful because at any point you can re-invert one of the signals and combine them so that any noise you picked up as a balanced signal is now canceled out. In general this is used to reduce noise caused by traveling through cabling. I believe that most audio devices that support balanced inputs convert these balanced inputs into unbalanced signals early on in an input stage--it is rather rare that an audio device does any amplification/filtering etc. on a fully differential signal.
Since many of National Instruments devices are intended to serve a wide variety of needs we do not specify in terms of balanced or unbalanced inputs since those are industry specific terms. However, when compared to this definition, the inputs on the PXI-4461 are unbalanced in that there are only two wires for each input, + and - (or + and reference if you use pseudo differential). That being said, I believe that most audio stores have boxes that you can buy that convert balanced to unbalanced signals or vice versa. If you want to use balanced signals to avoid cabling noise in your hardware setup then all you'd need to do is get one of these boxes to use for input and output with your PXI-4461.
This is a rather general comparison focusing on the topics that you've brought up. It may be helpful if you can re-phrase your question to ask about a particular capability of the PXI-4461 rather than a straight comparison. As far as the input signal type I don't see much of a difference between the two (assuming you get a balanced to unbalanced converter if you want to use balanced inputs--these are relatively inexpensive). As mentioned in the PXI-4461 Specification sheet, the input and output ranges are +/- 10 V and the rates are 204.1 kS/s. If you need more specifications like that I would suggest looking at that pdf, but if you'd like to describe your application a little more it may be easier to provide you with the information you're looking for.
I hope this helps, and please feel free to post back if you need further advice.
Cheers,
Brooks

My Ipod nano touch is not charging, not showing in my PC or laptop. Last I saw an apple icon and low battery signal. There after the screen is black and no power not taking AC or PC charge. What Can I do?

My Ipod nano touch is not charging, not showing in my PC or laptop. Last I saw an apple icon and low battery signal. There after the screen is black and no power not taking AC or PC charge. What Can I do?

If the Reset didn't work, you'll need to do a Restore.
From iTunes, select the iPad and then select the Summary tab. Follow directions for Restore. You will be warned that all data (apps, music, movies, etc.) will be erased but, as the Restore finished, you will be asked if you wish the contents of iTunes to be copied to the iPad.

Program to write signals from PXI 5105 using labview 2011

Hello
I am new in using labview. I need help in writing program to continuously record the signals form PXI 5105 using LabVIEW 2011. I prepared a program using help examples. It is recording the signal using pxi 5105 into the file after trigger. I tested the code using waveform generator with -100mV to 400mV, 1 kHz, sine wave. I have also attached the waveform of signal from the excel file recorded by the program. I have following queries
(i) Is the program correct to continuously record the triggered signals. Have I used the while loop correctly?
(ii) why some part in waveform is missing.
(iii) What should be the value of millisecond multiple ( I used zero)
I want to use above program for strain gauge signal measurement. Where I have to record the data at 20Ms/sec sample rate for 1 milli second after trigger.
thanks
Attachments:
Signal recording programme.vi ‏85 KB
recorded_signal.png ‏38 KB

Hi,
Sorry but I've only got LabVIEW 2010 so I can't open your file. If you can post a 2010 version I can take a look.
vinod_p wrote:
(iii) What should be the value of millisecond multiple ( I used zero)
If you are talking about the "Wait until Next ms Multiple" function then "Wiring a value of 0 to the milliseconds multiple input forces the current thread to yield control of the CPU." (from the context help for the function - press <ctrl>+h). Is this the behaviour you want?
Normally the ms multiple function is used to synchronise loops as it waits until the next multiple (be it 10ms or 10s) before continuing the loop.
-CC
"If anyone needs me, I'll be in the Angry Dome!"

PXI-4461 input protection?

Hi,
Is there any specification for the PXI-4461 input protection? I can not find any mention of it in the datasheet.
By misstake I connected an input to 60VDC and to my surprise it survived

Hi Janaf
From the manual the PXI-4461 Analog Input looks like this:
Input Overvoltage Protection
Differential configuration ............... ±42.4 Vpk
Pseudodifferential configuration
Positive terminal......................... ±42.4 Vpk
Negative terminal (shield) .......... ±10.0 Vpk
Best Regards
David
NISW

Low Mic Signal via Mbox2

More frustrated n00b questions:
I'm getting a really low mic signal into Logic.....
So in trying to research why, I'm spending HOURS combing the web looking for "mbox2 low mic signal", "Logic Pro low mic signal", etcetera ad infinitum, trying to find information. FINALLY I find, buried in a mess of search results, a single sentence on the Digidesign site indicating that rather than select the mbox2 driver in Logic, I have to use DAE (and I also have to download an update to the DAE). So I download and install the update, relaunch everything (a few times), and now am asked to authorize all of Digidesign's various third-party Plugins when I start Logic. Except that I can't activate them because my Mbox2 didn't come with an iLok dongle (which the box said I'd need a USB port for -- I dunno if it was supposed to come with one?). So I click through 20 different third-party-plugin failed activation dialogues as Logic boots, only to be told at last that Logic doesn't recognize any hardware attached. !
So where it was recognizing the mbox driver before, now it's not. (I was able to get a mic signal and record audio yesterday; but the level was VERY low, to the point of having to pump the levels so high that it distorted.)
I don't know if this is a Mbox issue or a Logic issue or a mic issue. I'm leaning toward an mbox/Logic compatibility issue but I'm trying to figure out how the f* to fix it. And my eyes are beginning to cross.
Help!

Doesn't the Apple Store sell mbox????? I'm sure they
used to if they don't now. I wish they wouldn't
recommend a product that proclaims itself a viable
substitute for things as fundamental as a preamp that
are not sufficient to be. (I haven't looked at the
Store; maybe they stopped recommending it.)
Thanks for the info
They used to sell the original Mbox, that is why I bought
one. I saw it on their web site sitting next to and plugged
into my the same Titanium G4 laptop I had. They even
had this whole web page about how great Digi products
would work on Macs. They had me all psyched about
getting pro stools. It only took a few months to see
the way things really were. After that, I did not
swallow everything Apple fed me. After I decided to
to try Logic things got ugly. Digi has a seperate audio
driver for people that want to use their hardware and
not their software. It is almost like
revenge for rejecting them. If you update OSX ( which
you would be crazy to do, once you discover this)
you always need to update their audio driver or the stuff
does not work and lets just say they are not very prompt
on the updates to this driver. I will eventually be getting
another interface and like you,I dont care if it is the
industry standard. I will never buy any Digi products again.
The only thing that keeps me from letting it go on Ebay is
that it has got a pair of high quality Focusrite preamps
in it. Digi, I guess thought that they were not as good
as their own (yea, right) so that is what they put in
the Mbox2, those cheesy 50db gain preamps. Well sorry
you had to a lesson the hard way. I try and persuade
people against buying their stuff but if you had tried
to persuade me before I bought mine, I am not sure
you could have done it. That web page Apple made
sucked me right in.

Differential inputs or pseudodifferential PXI-4461 inputs

I am wondering aboout the pseudodifferential an differential inputs of the PXI-4461
I am doing measurements on switch mode amplifiers where the outputs are bridged and not really ground (PGND) referenced. The input is ground (AGND) referenced to a 5V section. Due to switching currents, AGND and PGND can fluctuate relative each other.
I understand that the pseudo-differential inputs means the inputs are decoupled from ground and therefore suitable for common mode noise reduction. Differential are fully differential per input.
Is there any performance (accuracy) downside to the fully differential mode, compared to pseudo-differential?
How are maximum voltages specified for fully differential mode (max voltage relative to ground)?
Can I use one input channel of the PXI-4461 in differential mode, one in fully differential?
Thanks

I believe the information in this link would be helpful: Pseudodifferential versus Differential Input Configurations

PXI 4461 Coupling

Hi, all,
I am now using PXI 4461 to acquire data. This DAQ can provid AC or DC coupling, however I can not find this option in DAQ assistant subvi. I tried to modify this subvi, but it looks like that it is not a correct way. I attach what I have done and hope someone can help me to work it out. Thans a lot
Wu
Attachments:
Coupling.doc ‏64 KB

Wu,
You are very close! You're exactly correct in thinking that you need to add a DAQmx Property Node into the subVI. However, you'll need to move it from where you've initially placed it. I recommend that you put that same node immediately after the DAQmx Create Virtual Channel inside of the False case structure. Making this change will correctly enable AC Coupling for your input channel.
Thanks!
Regards,
Alan L
Applications Engineer
National Instruments

Low Amplitude Signal on PXI-4461

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