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

Similar Messages

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

How do I set the PXI 6031E for single ended or differential input?

6030/1/2/3 E manual states that the 6031 and 33E has software selectable single ended or differential input per channel. How do I set it in labview? I have been unable to locate the property.

Are you using traditional daq or DAQmx??
look at this VI to understand how to select this feature for both Versions of DAQ
any doubts, do get back
Regards
Dev
Message Edited by devchander on 03-08-2006 10:30 PM
Attachments:
mode.vi ‏23 KB

How can I connect the output of a BNC cable as a differential input to the SCB-68 block connector?

The output of a BNC cable has two lines, one for my voltage data and one for the ground. I would like to use the differential input mode of the SCB-68 connector block and i m not sure if i have to connect the ground to AI0 and the voltage to AI7 or the opposite, and also what is the name of this channel when i have to configure it using Labview. The DAQ card i m using is the 6036E.

Hi,
Because it just measures the potetial difference between the 2 pins it does not really matter. i would stick with the +ve going to the first channel of the pairing and then the -ve going to the second. You then have to go into Measurement & Automation explorer and create a virtual channel. In here you right click data neighbourhood and create channel....go through the steps, I.E analog input, device type, input type as just a voltage....and then on one of the later screens it tells you the exact pins to connect the wires to and gives you the option to select RSE NRSE or differential input type....as you change the connection type the pins guidance changes accordingly. its quite straight fwd and very easy to follow using this wizard.
Cheers
Lee

How do I do differential inputs with 5B devices?

I have the following hardware:
PCI-6071e, SC-2056, 5B-01, and 5b41's
I'd like to use the differential input mode, but I don't readily see how to hook-up the hardware.

Hello Phantom,
Thank you for contacting National Instruments.
It is not possible to use differential mode with 5B. You must use NRSE mode. Please see this KB for more information:
http://digital.ni.com/public.nsf/websearch/BDCD2656F6A8CFA7862562B4007A0DBF?OpenDocument
Regards,
Bill B
Applications Engineer
National Instruments

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

How do I get NIDAQ to allow 8 differential channels on a PXI 6031E card?

The PXI 6031E card contains 32 differential analog inputs (64 SE). However, in MAX, it is not possible to select Differential mode for any channels past the first 8. If you run the Test panels for the 6031E card (configured for differential input), selecting channels 8-31 results in an error. (0-7 operate correctly).

Yep! The URL has the answer. My problem statement wasn't quite accurate in that I claimed that I had errors on channels 8-31...Actually 8-15 and 24-31 were invalid and caused errors. What is/was confusing is that when editing an analog channel in MAX, and differential mode is selected, MAX allows the user to select invalid channel numbers(e.g. 8-15). The MAX editor requires the user to somehow "know" (or access the above URL) to skip 8 points to get to the next group of valid differential analog channels (16-23). It would be better if the channel number selector only displayed valid selections - based on the selected mode.

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

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

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

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

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

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 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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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

Differential inputs or pseudodifferential PXI-4461 inputs

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