Hardware buffered analog output single shot

Using DAQmx and M-Series hardware i'm trying to fire a single shot analog output buffered waveform. I need the output hardware timed. I'm able to output a hardware buffered waveform but can't figure on how to configure it for or stop it after prescribed number of cycle runs.
Thanks in advance.
Solved!
Go to Solution.

Hi,
You have a couple of options. You can set your timing to N
samples and you acquisition will stop when N samples have passed. Or you can
use a counter to control the clock of the analog output and then the counter
can be paused whenever you can. Before
we go and dig into the specific details of the scheme let me suggest a couple
excellent reading materials and let me know if they help. M Series Synchronization
with LabVIEW and NI-DAQmx, Continuous Analog Output
with Pause Trigger and Programmatic Grounding of Output in DAQmx, NI-DAQmx: Retriggerable
Analog Output -- LabVIEW and M Series: Analog Trigger
Source.
Also don’t forget to take a look at simpler examples like: Cont
Gen Voltage Wfm-Int Clk-Pause Trigger.vi
I hope it helps
Jaime Hoffiz
National Instruments
Product Expert
Digital Multimeters and LCR Meters

Similar Messages

Buffered analog output puts out additional sample on aborting or stopping task

I'm using DAQmx and LV 8.2
I'm doing a buffered analog output operation where the sample clock is driven by pulses from ctr0 on the same device (PXI-6070E). When I end the analog output task, either with the DAQmx stop task or DAQmx control task (abort option selected), the AO puts out one additional point from the buffer. (I have checked by setting breakpoints and stepping through the code that the additional point is definitely generated when the analog ouput task is aborted)
I need the output to remain where it was before the stop task command is issued. How do I fix this?
Thanks,
Marc

I'm watching to see if there hasn't been a sample output in a certain length of time, then terminating the task if there hasn't been. Specifically, I have ctr0 outputting pulses to drive the task based on input from the AnalogComparisonEvent terminal. I'm using a counter on a different PXI device to count the number of pulses and monitoring this count to determine if another sample has been output. I'm outputting the ctr0 pulse to PFI3 as well, and I'm monitoring both the ctr0 output (which drives the ao clock) and the analog output itself on an oscilloscope.
Basically I'm sitting in a while loop waiting for the monitoring counter to fail to increment. Then I terminate the while loop and stop the analog output task. I can watch the analog output on the oscilloscope while I step through the program. Immediately before the daqmx control task - abort (or daqmx stop if I don't abort first, or daqmx clear, if I don't abort or stop) vi runs, the analog output remains outputting the last sample. Immediately after the abort, stop, or clear, the analog output advances one sample in the buffer.
During this time, ctr0 does not output another pulse, so the scan clock should not advance.
Thanks,
Marc

I often get transfer errors -10608 and -10803 when doing double buffered analog output. How can I fix this?

I'm using the PCI 6711 board programmed in Visual Basic. I'm working from the WFMDoubleBuf example file for VB and I've modified it for continuous output on 2 analog channels. I fill the buffers with customized waveforms from files I have previously created. I often get -10608 (noTransferInProgError, No transfer is in progress for the specified resource) and -10803 (transferStoppedError , The on-going transfer has been stopped. This is to prevent regeneration for output operations, or to reallocate resources for input operations) errors when I try to output at higher rates (about 140000samples per second and up). The -10608 error generally happens after seve
ral (sometimes hundreds) of half buffers have been transfered, whereas the -10803 error usually occurs immediately after starting output. This device is supposed to be able to output at up to 1Msample per sec per channel but I don't seem to be able to do that. I have tried increasing the buffersize (up to 16777216) with no apparent effect. Is there any other information as to what causes these errors or how they can be avoided. Any ideas?

Roz,
I found two KnowledgeBase entries about the most common causes of these errors.
1. Why Do I Receive the Error -10608 When Using the PCI-6711?: http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/37752a79eb6a950886256c8b006e8870?OpenDocument
2. Why am I Getting the 10800 and/or 10803 Errors?:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/c9097c72463d215886256a700075a6ef?OpenDocument
Have a great day.

How much noise expected in analog output?

I'm using a PCI-MIO-16E-4 with LabView to generate buffered analog output, and at the BNC-2090 output (DAC0/1OUT) I'm finding ~180 Hz hum of about 20 mV peak-to-peak. It doesn't seem to matter whether I'm writing a waveform or not; the noise magnitude is always about the same.
Is there something I can do to eliminate or reduce this, or is it typical so I'm stuck with it? I futzed with the BMC-2090 shield ground jumper (W1) but none of the three documented settings made any difference.
Any suggestions would be greatly appreciated.
thanks,
Kevin

No particular noise is "typical." No noise at all is atypical. 20mV is low enough that it could be radiated noise for nearby equipment. I doubt you card would have that noise in the lab situation where they test for noise. Which essentially means something about you estup is responsible for the noise.
Since the frequency is a multiple of 60Hz it is probably environmental noise, radiated ot picked up off of the ground. Really and truly, 20mV is not a lot. I have acquisitions where I must be very careful in grounding ALL the associated equipment or I see huge blurts of noise from a motor drive - on the order of 3 Volts until I drove an eight foot gound rod through the floor to get an isolated safety ground for my DAQ PC and scope. I still see the noise, but it is now lower than 0.8V so I don't get false triggering of TTL circuitry from it. This is AI not AO like you are discussing.
If you check the specification of your card there is a table on "System noise." I am not saavy enough to understand it, but I see that the noise is dependant on the output range. I suspect that the range is not a user selectable item, but in theory if you see more noise than the spec sheet says, then it is part of your setup not the card.
Here is part you really don't want to hear: Solving a noise problem by text messaging is like solving a mental illness over the phone, maybe worse. I can tell you all sorts of practical, common sense things that are not specifically helpful. I can tell you from personal experience that you really need to follow all the good practices you can, if you really want to have as high a SN ratio as possible.
Can you set up a single point ground? Can you eliminate all ground loops (shielding only grounded on one end.) I had a stray strand of shielding that brushed against a case that made terrible noise once.
There is a good book called ,"Grounding and Shielding Techniques," by Ralph Morrison from Wiley Inter-Science. There are papers on this in in the tech resources of ni.com. In particular the paper on "Field wiring" is good. Keithley has a good book they will send you for free on low level measurements that is very informative. You have to call them on the phone to get it.

Single shot analog output: How to pulse this. Probably easy, I'm at a loss.

Hello.
I have a piece of machinery that my system is connected to. Every time it reaches a proximity sensor (It's a reciprocating unit), I need to do a single pulse of 5v out of my analog output. It has to be fast, it has to stop until the sensor is reached again, and it can't stay 'on' for long.
I've attached my VI. I'm using a voltage input via DAQ assistant, routed through some logic to produce a 'true' boolean every time that sensor is reached, and that boolean is connected to a case structure with voltage out tasks created in DAQmx.
My problem is that the machine won't reverse while the case is still true and there's still the 5v being called by the true case on the case structure. It has to pulse, then stop, then be allowed to come back when the proximity sensor is reached again. As it is now, the machine reaches the prox and then the whole system stops, as the 'true' condition on the case structure, and subsequent voltage output, remain high.
I've attached the VI and heirarchy as well.
I've tried a few different things here, as well as just using a DAQ assistant with N samples, but that would just retrigger when the loop repeats anyway.
I'd love to sit and bang my head against this til I get it, but I'm under a time constraint. Help!
Still confused after 8 years.
Solved!
Go to Solution.
Attachments:
using create channel.vi ‏94 KB
logicsub.vi ‏32 KB

Ralph, without knowing the exact DAQ card that you are using, it is difficult to give you the best solution. If you want to continue with the solution that you currently have, try adding a shift register to the outer while loop to track the previous value of the boolean. In this way, we can keep multiple values that are above the threshold from causing multiple pulses. Next add a time delay after the DAQmx Write, then add another DAQmx Write to set the output back to your low value. Remove all code from your "false" case. See attached VIs. Please let us know what model of DAQ card you have as we may be able to do something clever like a retriggerable pulse train if your card can support it.
Charles Chickering
Charles Chickering
Architecture is art with rules.
...and the rules are more like guidelines
Attachments:
using create channel.vi ‏98 KB
logicsub.vi ‏29 KB

NI-DAQmx VisualStudio C++ 6 Single point analog output

Specs: NI-DAQmx 7, VisualStudio C++ 6.0, PCI-6722,8channel AO
We have a very simple application: set a voltage (actually 6 channels) and keep it until we want it changed again, perform the change very quickly in response to an image capturing algorithm. So I don't need any waveforms or buffering.
In this forum post http://forums.ni.com/ni/board/message?board.id=231&message.id=3283&query.id=18094 you talk about an AOOnePoint example, but I get an error that the NI-DAQ driver does not support my device.
I may need to use NI-DAQmx, but how? I would like to use something like AO_VWrite(,,), maybe for 6 channels in one call. But I can't find it in NI-DAQmx. It seems I need to setup buffers and frequencies. I have a working sample, but it seems a slow and certainly overkill of this simple application:
// Link with \DAQmx ANSI C Dev\lib\msvc\NIDAQmx.lib
#include "NIDAQmx.h"
double[2] data;
int taskHandleAnalog;
int written;
void Init()
    DAQmxErrChk (DAQmxCreateTask("",&taskHandleAnalog));
    DAQmxErrChk (DAQmxCreateAOVoltageChan(taskHandleAnalog,"Device and Channel Info","",0,10,DAQmx_Val_Volts,NULL));
    DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandleAnalog,"",1000,DAQmx_Val_Rising,DAQmx_Val_ContSamps,NUMBER_OF_AO_SAAMPLES));
    DAQmxErrChk (DAQmxWriteAnalogF64(taskHandleAnalog,NUMBER_OF_AO_SAAMPLES,0,1.0,DAQmx_Val_GroupByChannel,data,&written,NULL));
    DAQmxErrChk (DAQmxStartTask(taskHandleAnalog));
void SetVoltage( double voltage )
    data[0] = voltage;
    data[1] = voltage;
    DAQmxStopTask(taskHandleAnalog);
    DAQmxErrChk (DAQmxWriteAnalogF64(taskHandleAnalog,NUMBER_OF_AO_SAAMPLES,true,10.0,DAQmx_Val_GroupByChannel,data,&written,NULL));

Hi,
It looks like you simply wants to output voltages on the analog output channels, but only wants one update at a time with no waveforms or buffering in DAQmx.
As I'm sure you know there are really just 3 types of measurements. Single Point, Finite, and Continuous. Since you want a single value at a time it's just a Single Point operation.
You can find DAQmx examples for single point operations in this path:
C:\Program Files\National Instruments\NI-DAQ\Examples\DAQmx ANSI C\Analog Out\Generate Voltage\Volt Update
Simply place the DAQmx Write Code within a loop and you will be updating one value at a time, but multiple times when "we want it changed again".
Dennis Morini
Field Sales Engineer
National Instruments Denmark
http://www.ni.com/ask

Storing analog output data in a datatype other than single-precision

I'm using three PCI-6713 AO cards in a single computer to output 24 channels of data using Labview 6.1. The input terminals of all the analog output VI's are of type single precision (32-bit). The output cards only have 12-bit DAC's, so there is a large amount of information stored that is never used by the cards. Is there a way in Labview to store AO data in another, smaller datatype - such as a 16-bit integer. This would greatly reduce the memory requirements for my application.

I just figured out the answer to my own question. There isn't an option for binary in the AO Write vi, but if you go down to the AO Buffer Write vi (which is called by AO Write), you can select binary array.
Thanks for all your help.
Josh

Synchronize hardware timed buffered counter acquisition with buffered analog input acquisition

LV7.1
DAQmx
PCI-6036E
SC-2345
Windows 2000
Greetings.
I am simply trying to synchronize AI readings with readings from one Counter.
I am trying to perform buffered analog input synchronized with buffered counter acquisition.
I'd like the AI acquistion to trigger the Counter acquistion.
I'm currently setting the Sample Clock Source for the CI Cnt Edges Task to "Dev1/ai/SampleClock" but when I try and set the source for the "DAQmx Trigger" I can't seem to select one that works. I assumed that the source should be the "Dev1/ai/StartTrigger" but that produces and error as does selecting any of the PFI's.
I'm new to DAQmx and didn't have any luck with the examples or what's been previously posted.
Thanks for your help.
Attachments:
Initialization.jpg ‏84 KB

Gentlemen-
All of your initial help was great. I had some noise on my counter lines so switched from an E-Series card to a PCI-6259 M-series card in order to use the counter digital filters.
Now I can't get a corellated buffered counter and buffered analog input acquistion to work. This same code worked fine on an E-series card but it doesn't on the M-series.
I verified that the source and gate of the counter are working properly using the test panel and a external function generator.
But when I run the attached code I get no data out of the "Counter 1D U32 NSamples", only an error saying that the timeout of the function was reached and no count data became available. Am I missing the specification of a another clock or something?
The counters also work fine using the M-series example code "Count Digital Events (M-Series DAQmx) but this is not a buffered acquisition.
Any help would be greatly appreciated.
Steve
Attachments:
Sample_Code.jpg ‏136 KB

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

I am trying to generate an analog output for the following waveform:
Pulse width: 300 usec, Frequency 40 Hz, Amplitude is following a sine wave with a 2 second period.
My approach is: Use an async timer with 1/[40 Hz] sec interval. I set the DAQ output rate at 1 MHz and the approach has been to generate and write 300 samples of the amplitude I need to send out, then wait for the next async interval callback , update amplitude etc etc. The assumption is that once the 300 samples are written and the task started , a 300 usec pulse would be sent out , task then stopped and then the analog output would be set to 0 waiting for he next pulse. The reality is that I get a stream of pulses of 300 usec which last the whole timer interval.
So , trying to establish whether what I am trying to do is feasible without actually sending a large array to the USB-6251 which would write zeros for the period after 300 usec.
Here is my timercallback code for review:
    switch (event)
        case EVENT_TIMER_TICK:
            DAQmxErrChk(DAQmxStopTask(TaskAnalog));
Determine Voltage value algorithm here
           //Generate Waveform and start Task
           //Prepare AO arr
           for (k=0;k<300;k++)
               AOArr[k] = 0;
               if (k<G_PulseWidth)
               AOArr[k] = VOLTAGE_OUTPUT;
           if (AOArr!=NULL)
               DAQmxErrChk(DAQmxWriteAnalogF64 (TaskAnalog, (int32) 300 , 0, DAQmx_Val_WaitInfinitely, DAQmx_Val_GroupByChannel , AOArr, &sampsPerChanWritten, NULL));
            DAQmxErrChk(DAQmxStartTask(TaskAnalog));
           break;
Thanks

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:
DAQmxErrChk(DAQmxCfgSampClkTiming(TaskAnalog, "",1.0E+06, DAQmx_Val_Rising, DAQmx_Val_FiniteSamps , 300));
THis did it. works very well.
THanks

How can I use two analog output channels simultaneously?

I am using PCI6110 DAQ card. I want to run two separate VIs on one computer. Each VI output a waveform to one analog output channel. How can I do this simultaneously without interfering each other?
Thanks

Hi Stephen,
This can NOT be done with two seperate VI's.
The issue is in the hardware/driver.
Your hardware has a clock that controls how fast updates to the AO occur. That clock can only have one value at a time. I will let your contemplate the complications that come up with two different clock settings being active at the same time (see below).
So how do you work around this complication?
You will have to develop a single VI that OWNs both output channels. That VI will have to accept start,stop,configure, etc commands from the two clients (what you will have to convert your existing VI's into). If you decide to place a restriction on the services you provide to the clients along the line of "only one sample rate at a time" you will be making your li
fe much easier.
If I was contracted by a customer to do what you have asked, I would try to combine the two existing VI's into one or simply buy a second 6110 and avoid all of the hassles. Both of these approaches would end up saving the customer money in the long run while freeing them of any restrictions that where established in order to develop the "server".
I hope this helps,
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Usb 6009 continuous analog output

Hi
I'm pretty new to Labview, so you may have to bear with me. I have a USB-6009 and I want to generate a continuos analog output voltage. I've got the example you have posted 'Gen Mult Volt Updates-SW Timed_LV7.1 (0 to 4).vi' working and it outputs a continuous sine wave.
In a similar manner I need to generate:
1. Ramp up voltage (and ramp down voltage): starting with a continuos constant voltage, which after a period of time linearly increases to another constant voltage, and which allows me to specify the 3 time intervals and the rate of increase.
2. Pulsations: whereby I can specify the amplitude and time interval of each pulsation
This is so that I can control voltage to a valve which regulates my pipe flow. In the example I have (one stated above), I do not understand specifically:
i. Why I need both a 'Software Loop Time (ms)' as well as 'Timeout'
ii. The 'Sinusoidal Pattern' input which seems to generate data for a sine wave- I can't get a description of that and there are no similar VIs for other waveforms; and what is the function of the two numbers it has?
iv. How do I change amplitude and time period for the wave?
iii. What does 'Index Array' do?
thank you

Hi there,
I'm guessing the VI you are using is the one from this KB:
http://digital.ni.com/public.nsf/allkb/6F2C2B49A89D685C8625711D007BDD64
i. The software timed loop control is to control the rate at which you change the voltage output. The timeout on the DAQmx Write VI is the maximum time in seconds the VI will wait to output a sample (eg. if the write buffer is full, the Write VI will wait for it to become available for 'timeout' seconds before outputting an error).
ii. The sine pattern is just an array constant of doubles that make up the sine wave voltage values, and the for loop adds an offset (of two volts) to every single one of those values. You might want to replace that entire array constant and for loop with a Simulate Signal Express VI (just search for Simulate Sig or look in the Functions >> Input palette) and convert the dynamic data output to an array of doubles. You can configure the type of waveform, amplitude, and time period from that express VI as well.
iii. Refer to previous answer.
iv. Index array returns an element of an array based on the index input. You can turn on the context help and move your mouse over functions to get more help on them.
I hope that helps!
Way S.
NI UK Applications Engineer

Usb-6009 analog output voltage

Hi,
The usb-6009 has two 0-5 volts analog ouputs. Is it possible to connect
them in series, in order to get a single 0-10 volts analog output
channel ?
Thanks,
Nicolas

Those are ground-referenced signals. To connect them in series, you would have to connect one of the outputs to ground. You would be shorting out (at least) one of your analog outputs, and probably damage the unit.
John Weeks
WaveMetrics, Inc.
Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

2 analog output channels with different frequencies

Hi,
hope that somebody can help me:
I created two physical tasks, analog output channels.
I should give signals (triangle signals) to a scanner. The problem ist that I need these triangle signals with two different frequencies.
I can create the signal with each of the task, but not together. Can I solve this problem somehow?
Ah, and of course the 2 tasks should start together...
Thanks for your help!!
Telly

You didn't mention the type of device you're using, so I'll assume it's a standard MIO. A typical MIO only has one AO timing engine, so you'll have to create one task for both channels and use a single update rate for the task. You will have to make the output frequencies different by passing different data for both channels.
For example, let's say your update rate is 1KHz. The data for channel 0 is 1000 data points of a single cycle of a triangle wave. The data for channel 1 is 1000 data point of two cycles of a triangle wave. When you run the task, you will get a 1Hz triangle wave on channel 0 and a 2Hz triangle wave on channel 1.
Good luck,
Joe

How to avoid delay during analog output generation by changing its frequency?

Windows XP
LabVIEW 7.1
PCI-6036E + BNC-2120
Hi,
I am going to create a vi to generate an engine speed sensor signal (a simple square wave with specific missed pulses, in my case 58 pulses “teeth” and 2 missed pulses “missed teeth”) as an analog output but in addition give me the opportunity to control parameters for example frequency online to simulate the engine speed changes during running that vi. For this purpose I have started with “Continuous Generation.vi” which is available in NI Example Finder under the following path:
Hardware Input and Output > Traditional DAQ > Analog Output > Continuous Generation.vi
Then I modified it towards above mentioned goal, all related vi s are attached. The main vi is: "Motor Signal Generator_1.12.vi"
At the first try it looks that it works properly but when have a look on that more accurately with Oscilloscope (fortunately I have a good one: Agilent 54621A – 60 MHz, 200 Ms/s) obviously there is a gap (delay or Jitter) whenever I change the engine speed. It is also attached in Signal generation_problem report.doc file.
Note: Small gaps are OK and related to predefined missed teeth but the big one is happened during changing engine speed.
As far as I understand it is related to the time which case structure in AO C-GEN sub-vi needs for AO reconfiguration each time after changing the engine speed (update rate). How can I get rid of this delay or gap during signal generation and generating completely continuous signal?
I have to mention that obviously I changed the frequency by changing the update rate. The other possibility is to change the number of updates in one period (refer to "generate arb frequency.vi" in NI site: http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3E48F56A4E034080020E74861) which resulted in no delay however then I can not change the frequency continuously but step by step (for example jump from 5Khz to 2.5KHz immediately) and this can not pass to my application.
Any hint is appreciated.
regards
Attachments:
Signal_generation_NIsupport.zip ‏81 KB

Hi Roozbeh,
The following example will allow you to vary the pulse train frequency during run time.
Thanks,
Lesley Y.
Attachments:
GenDigPulseTrain-ChangingSpecs.vi ‏75 KB

Which audio interface(s) for 16 to 20 analog outputs?

Hi. I wonder if anyone can help me...
I'm running Logic 7.2 on a black MacBook. For my inputs I am using the MOTU 8pre, as this is convenient especially when recording drums with my band... no scrambling together of pre-amps... no faff...
The thing is... I've been given a shed load of gear (literally), including a 24 channel analog mixing desk and tons of outboard rackmounted effects units/compressors/gates...
I would REALLY love to integrate the two systems, especially at the mixing stage, by routing my Logic tracks to the desk. Unfortunately, the MOTU 8pre only has a couple of analog outputs (+ headphone out).
To make this a venture worth undergoing, I'm going to need a minimum of 16 analog outputs. 20 would be great if possible.
I suppose my initial questions are:
1. Can I daisy-chain 2 firewire audio interfaces (each with 8 analog outputs) to give me a total of 16 analog outputs?
2. Bearing in mind I have a low budget, could anyone advise me on which units to get. I don't think I could afford any more MOTU gear, unless I find an amazingly low priced second hand item. What about Edirol or M-Audio?
Thanks in advance.
MS

This is worth checking: http://www.ioneconnects.com/product.shtml
Based on new DICE II firewire chip with JetPLL technology (should have much lower jitter than regular firewire Audio devices that are not built on DICE II).
I believe that you can choose the configuration you need.
The only question for me is whether they are affected by apple's firewire streaming bug. But as I've heard that in the info of 10.4.9 SDK is a statement, that core audio bugs were repaired, I hope the offset streaming problem will be finally the past...
Man I am really considering this firewire snake, as it definitelly has many ins and outs - including 4 AES/SPDIF in and out!!!
I am going to upgrade my studio and two of those will probably give me enough ins and outs for all my needs (musicians + outboard hardware and a summing mixer). I was also thinking about Symphony (PCI solution seems to be still more stable than firewire) and some I/O "modules" from apogee, but that is much more expensive. And I 've read only positive info about the DICE II, so maybe I will give a firewire another chance...

Hardware buffered analog output single shot

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