Is any extra isolation required when using Analog output to dirve higer power circuitry?

I want to connect the analog output of a DAQcard-1200 to a current amplifier to give 5A and a tranformer to give approx 200V, is any extra isolation required to protect the card?

Hello;
As long as the maximum current that the board can source is taken in consideration and the input impedance of the external circuitry is high enough to prevent signal reflections back to the DAQ board, you should be good to go.
However, since the protection circuitry can be built with such little budget, I wouldn't take my chances. I would go ahead and include the protection circuitry anyway.
Regards
Filipe A.
Applications Engineer
National Instruments

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Attachments:
M22PitchPlunge.zip ‏524 KB

Brian,
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provided here.
Of course the accuracy is limited by the accuracy of the onboard
oscillators of the board but this shouldn't be really relevant.
Generating triggers based on 2D position data is not a trivial
task. I have tried to examine your program but it's a bit hard to read.
I had a look at your onboard program. I don't understand exactly how
you determine if the axes have reached a trigger position or not. It
looks like you are only reading values from buffers. For an exact match
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from the axes and compare them with your trigger position buffer. In
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some deviation from the ideal trigger position (see image).
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either try to implement the more advanced comparison in your onboard
program but I'm not sure if this will result in the performance you
need. The 7350 provides only a limited amount of CPU power for onboard
programs. At last it all comes down to the question how good your
deterministic real-time behavior needs to be. If some ms delay and
jitter are ok for you then you probably could stick with this approach.
If you need a better real-time behavior you should consider using
either an additional real-time board like the PCI-7041/6040E that could run the 2D trigger algorithm or a PCI-7830R board that could run the algorithm on an FPGA.
There are even more options including the NI SoftMotion Development Module to design your own motion controller using LabVIEW RT but again, this depends on your application needs.
Best regards,
Jochen Klier
National Instruments Germany
Message Edited by Jochen on 09-09-2005 10:47 AM
Attachments:
Image1.jpg ‏19 KB

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PXI-5660 / 5620. What is lowest reasonable voltage when using Analog Edge Trig?

Presently, I am using Analog Edge Ref Triggering on the PXI-5660. The lowest voltage that I can set the trigger level to is 0.200 volts without noise causing the trigger to occur. Is this level reasonable? Is there a way to reduce the noise so that the trigger level can be set lower?
I graphed the waveform coming out of the niScope MultiRead Cluster.vi in the ni5660 Read Average Power Spectrum.vi. The noise on the graph was as high as 0.190 volts. I thought that I saw the noise down to 0.010 volts at one time.
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Thank you for your response.
The reference level I am using is 0 dBm.
I ran the ‘niScope SMT Power in Band.vi’ example with dithering enabled and disabled. I could see the noise when dithering was enabled and the reduced noise or no noise when dithering was disabled. See attached .jpg’s. I added ‘Waveform Graph 2’ to display the output of ‘niScope Multi Read Cluster.vi’.
In my application, I disabled dithering and put the trigger level lower. It now works.
Disabling dithering needs to be set after ‘ni5660 Configure for spectrum.vi’. Inside the ‘ni5660 Configure for Spectrum.vi’, a vi called ‘SMT Configure RFSA for Spectrum.vi’ enables dithering. ‘SMT Config niScope for Spectrum.vi’ is another vi that enables dithering.
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Attachments:
SMT Power in Band with 50 ohm termination on input of 5620 Dither Disable.jpg ‏100 KB
SMT Power in Band with 50 ohm termination on input of 5620 Dither Enable.jpg ‏106 KB

Avoiding Resource Reserved Error -50103 when using Independent Outputs

Hi all,
I'm currently working on a VI for performing Auger spectroscopy. Part of the program acts as a lock-in amplifier for focusing on the the amplitude of an input waveform at a specified reference frequency and another part should act as a kind of sweep generator. In the main execution loop of the program, I first want to set the sweep control, wait for an appropriate amount of "settling time," and then read the input waveform and perform the lock-in analysis. At the beginning of each loop iteration, the sweep control should be incremented by a small amount. I was able to complete a VI which performed all of these tasks successfully (with the help of a few topics I found here on the forums).
Up to that point, I had been using an external function generator to create the reference waveform, which would be read in to the program so that its frequency could be measured for the lock-in section of the VI. In an effort to conserve ADC resources for the primary input channel, I decided to try generating the reference with the second DAC on the NI PCI-6221 that I'm using. After creating a second output task to which I assigned the other physical output channel, I set up a waveform buffer for generating the desired sine wave, and then I promptly started running into these pesky resource errors. I understand now that setting up the outputs in this manner will not work since the first output task created will dominate all of the resources of the DAQ; the best solution to the problem I came across on the forums was to come up with a scheme of condensing the two outputs into a single task.
The trouble with this approach is that my two outputs have very different requirements. There is the reference signal, which should be written continuously for the duration of the VI's operation (i.e. as soon as the user specifies a frequency, this output should begin acting just like a function generator). And then there is the sweep control, which should be re-written for every execution of the main loop with gradually increasing DC values.
Is there any way that I can configure the output task so that I can treat these two channels as if they were independent? At this point, it is starting to seem like my best bet might be keeping the reference signal as an external input, even though this would mean sacrificing a great deal of my ADC capabilities.
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P.S. - I am not including a copy of my VI since the block diagram is cluttered with the input methods (which work just fine). My problem can essentially be reduced to that of generating a DC signal that increments with each iteration of a loop while simultaneously generating an unbroken sine wave.

Let the analog generation rate and the number of samples per generation set your loop timing. Don't add any additional wait functions. Doing so will goof up your analog generation.
The way the code in the picture is set up, the loop will iterate every second. This is because I set the clock sample rate to 1kHz, and set the waveform generation number of samples to 1000. It takes 1 second to generate 1000 samples, therefore that's the amount of time it will take the loop to execute. Because the generation is performed in hardware, the analog generation is still continuous.
If you want your loop to take longer to execute, adjust those numbers. For instance, when you generate your waveform, if you set the number of samples to 2000 and leave everything else the same, the loop will take 2 seconds to execute. If you were to set the number of samples to 500 and leave everything else the same, the loop would iterate every 0.5 seconds.
Does that make sense?
Also, be more specific than "the program stops working right". That tells me absolutely nothing. What, specifically, no longer works correctly?
I've attached an example, which is basically the same thing I showed earlier, except that I've added some code that calculates the loop iteration time, so you can see for yourself how changing the number of samples in your waveform affects your loop speed.
One other thing to keep in mind that's very important: if you have other code in your loop which takes longer to run than your analog generation, you are going to run into problems with your analog generation. The loop won't iterate until everything inside it has finished executing. If your analog generation takes 1 second, but you have another subVI which takes 2 seconds to execute, your loop will take 2 seconds to execute, leading to analog generation buffering errors.
You only want a single timing source in your loop. When you're doing hardware-timed analog generation or acquisition, that should be your timing source. Does that make sense? From your original description, it sounds like you might want to consider a different architecture, something more like a producer/consumer. If your analog generation needs to be continuous, you probably want it in a separate loop. You can use queues and notifiers to communicate between loops.
Attachments:
analog out example.vi ‏33 KB

Using analog output in the background

Hi,
I need to use the analog output channel on a NI PCIe-6351 to play an audio signal, and while the signal plays i need make some changes the UI dialog box, is it possible for me to move the playing of the audio to the background and proceed with program execution?
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#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
#include<math.h>
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int32 error=0;
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float64* AIOSample;
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DAQmxErrChk(fnCreateTask(&AOtaskHandle));
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puts(errBuff);
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The program reads a 10 seconds long 1kHz sine wave signal from a WAV file and plays it over AO0.
I want the program to print "Playing Audio" on the console window while the audio is still playing, i.e when DAQmxWriteAnalogF64 is executing.
I'm using Visual Studio 2005 on Windows XP and an NI PCIe6351.
I'd really appreciate any help I can get.
Thanks a lot!
RaziM

Hi RaziM,
It sounds like you will need to implement some sort of multithreading to accomplish playing audio in the background and also making changes in the UI dialog box in the foreground. Since DAQmx is thread safe this should definitely be possible, but it will probably take a little more work on your part.
You may want to take a look at this page which gives a walkthrough to Multithreading with a Background component, http://msdn.microsoft.com/en-us/library/ywkkz4s1.aspx
Here is another forum post about how DAQmx runs multiple threads, http://forums.ni.com/t5/Measurement-Studio-for-VC/DAQmx-how-does-it-multithread/td-p/221953
I hope some of this helps!
Rachel M.
Applications Engineer
National Instruments

Using analog outputs in labview with

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I have used the PMD12208FS and I used this vi to use the analog outputs for it. I obtained it from Measurment Computing ftp site. The data value is in mV. Hope this helps.
Attachments:
PMD1208FS_AOut_lv61.vi ‏17 KB

How can i deliver a single pulse of varying amplitude using Analog output and USB-6251?

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Determine Voltage value algorithm here
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I did resovle the issue I encountered. It was due to bad configuration of the Task.
My initial configuration was:
DAQmxErrChk(DAQmxCfgSampClkTiming(TaskAnalog, "",1.0E+06, DAQmx_Val_Rising, DAQmx_Val_FiniteSamps , 300 * 1.0E+06));
which should be:
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THanks

Is any extra isolation required when using Analog output to dirve higer power circuitry?

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