Problems using acquire waveform...

We are trying to read an accelerometer signal using AI Acquire Waveform(it didn't work with similar boxes either).
The problem is that we set a scan rate of say: 10k samples/s and number of samples of 10k.
So every second the buffer is refreshed(so we can see the graph) and there is a big distortion.
Distortion is always the lenght of the buffer. We could do a "blind" acquisition setting a big buffer(# of samples). That would solve the problem but it shouldn't be like that.
Thanks,
Erick

Could you explain a little more what the distortion you see looks like?
Mike...
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Using the NI tkds 30xx library, but there is a problem with acquiring waveforms

When I try to use the Initiate Acquisition function that is part of this library, I get the following error message: "the given session or object reference is invalid." The name of the device (created by the "initialize" function) seems to be correct (when I probe it). It is: "GPIB::1::INSTR 4". Does anyone know how to fix this?
Sean

Hi Sean
find attached an example, how I've initialized
TEKTRONIX TDS7054 DPO-scope. It was made for
a special application - should demonstrate,
how the address has to look like......
( at that time as I made it, was no driver available
from Tek / Natinst - thatswhy I have reused one )
regards
wha
Attachments:
tds7xx_init.zip ‏128 KB

Error 10401 occurred at AI Hardware Config, when using AI Acquire Waveform vi

I can successfully run applications that use the AI Sample Channel vi, however when I use the AI Acquire Waveform vi the following errors are generated:-
Error -10401 occurred at AI Hardware Config, followed by
Error -10401 occurred at AI SingleScan.
All applications have been developed using Labview 6.0.2, on an NT machine. The applications are then run (or atleast attempted to be run) using the Labview Run-Time Engine on a different NT machine.
The driver software I am using is the NI-DAQ Native Data Acquisition Driver Software Version 6.1.

Hi,
I've found a Knowledge Base on the NI website describing some situations where this problem occurs:
http://digital.ni.com/public.nsf/websearch/46F78EDD19BA0CC386256CEE007201FC?OpenDocument
That error code is generally seen when something has changed in the DAQ card's configuration, or the drivers are not installed properly. It's strange that this is showing up only on certain functions for your application.
Also try having a look through the DAQ troubleshooting pages on the website:
http://www.ni.com/support/daq/
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Mark Lee
National Instruments

How to use AI acquire waveform.vi for continuous acquisition

Hello all,
I am using LabVIEW 5.1 and PCI-6023E to acquire a voltage signal continuously, display the acquired data on a chart(display one minute of data at a time)then save all the acquired data to a spreadsheet file.
When I used the random number as a signal to develop my program; everything has worked as expected. However,it is not working now as I replace the random number with a real voltage signal using the AI Acquire Waveform.vi. I have encounterd several problems:
1/ Only display one second of data at a time.
2/ The elapse time that I have calculated does not match with the time display on the chart.
3/ The program runs very very slow when I increase the number of scans
to acquire to 1000, but my program need to acquire the signal for 15 minutes at a rate of 50Hz(50sample/second); it is about 50,000.00 samples.
Do you have any idea how should I do to make it works? I am a novice in LabVIEW; any help would be greatly appriciate.
Hao
P.S: I've attached my program if you want to take a look at them.
Attachments:
Acquire_Using_Random_Number.vi ‏89 KB
Continuous_Acquire.vi ‏96 KB

Helleo Labviewguru,
Yes, I did tried to see those examples but I could not display on a chart nor store to an array and save to a spreadsheet file when I used the AI Config.vi, AI Start.vi and the AI Read.vi(in a while loop). Can you please help me with this.
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Hao

Can I acquire waveform at faster sampling rate using external clock?

I am trying to acquire waveform at a sampling rate of 1MHz. My 6036E card is maxed out at 200KHz. Is there a way to achieve a sampling rate of 1MHz using an external sample clock? Your PFI pin can take external clock as an AI sample clock, right?

Hi,
I remember I asked the similar question before in the NI forum, they reply me:
the max sample rate (scan/s/channel) cannot be greater than your board max sample rate, even you use external scan clcok. So the answer is no for your case.

Problems with getting waveform using tektronix tds 6604

hello,
i'm using the scope tds 6604 with tektronix
lv-driver (TKTDS6K) under lv 6.0.2.
I always want to read the displayed waveform via GPIB.
This is not a problem. The waveform and the scales are correct. BUT if I stop the aquisition on the scope
Run/Stop-Button) and then change the time- or
amplitude-scale or the position of the graph on the scope, I read the correct waveform but the scales are incorrect. I tested it for a while but I could not see a system. Perhaps do I have to use some mathematical operations with the array, in order to receive again the correct scalings and positions?
thanks in advance, sven

without looking at the actual LabVIEW driver, my guess would be that the VI's graph settings are obtained by the VI that you use to programatically set vertical and horizontal settings of the scope. If you manually change the scope, the capture waveform VI has no idea what the settings are because all it does is retrieve the waveform and doesn't do a query to get updated scope settings. If mixing program and manual control is soemthing that you need to do, you'll have to add the code to query the scope for it's settings. Most drivers don't have these queries because typically, only the program is in control.

How can I find an example about acquiring waveform data by software trigger using PXI 4070 DMM?

Anybody could proivde an example or simliar about acquiring waveform data by software trigger using PXI 4070 DMM?
Thanks!

hi there
from the NI main page go to the developer zone http://www.ni.com/devzone/dev_exchange/ex_search.htm. select "LabVIEW" and "Digital Multimeter (DMM)" and search for "4070". then you'll find some examples.
Best regards
chris
CL(A)Dly bending G-Force with LabVIEW
famous last words: "oh my god, it is full of stars!"

Ai acquire waveform.vi

Hi,
Recently I receive a code from my senior to read data from DAQ bnc-2090. I have installed DAQmx 9.3 but I cannot run the code due to "cannot load ai acquire waveform.vi." I have find the answers that an old version of DAQ driver is needed. However, TDAQ driver is only suitable for Windows XP/2000, and I use Windows 7. What should I do to solve this problem? Thank you.

The only driver for that card is traditional DAQ and you've already found out that it is not supported on Windows 7 so why this question?

A question about "AI acquire waveform.vi ".

I use my DAQcard(PCI-6024E) to acquire two AI signal at the same time through AI acquire waveform.vi.
But it is getting into a serious delay on my executing progarm by monitoring my time depended plot or time-counter(It is about 5 seconds in the real world vs. 1 second the program runs.).
however,I didn't encounter that problem when altering another AI vi(AI sample channel.vi),but it couldn't conform to my needs.
My AI acquisition program structure is "AI acquire waveform+equi-Ripple lowpass+mean" and another is "AI acquire waveform+mean".All settings are default except the high and low limit.So,does anyone solve my troubles?I really need help!!
(The situation is Labview 5.1 in the PC of p-133,32MB,and more than 1G reserv
ed capacity for C
thanks a lot!

Hello;
The best way to go about that is to use the Labview shipping example named Continuous Acquisition and Chart (buffered).vi that you can find at Search Examples->I/O Interfaces->Data Acquisition->Analog Input->Continuous Analog Input; as the start point for your development.
That vi shows the best way to do a data acquisition. You can insert you average VI inside the while loop of that VI.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments

AI Acquire Waveforms High and Low Limit

Hey everybody,
I am currently working with Labview 7.1 and a daq card. I am collecting 4 channels and using ai acquire waveforms to do this. I want to have different high and low voltage limits for each channel though. Is there a way to do this with ai acquire waveforms or would can I use something else.
Thanks for the help!
Devon

Hey Devon,
In addition to what David said, there is a great knowledgebase article here with more information about setting multiple ranges for Analog Input. The Traditional DAQ vi, AI Acquire Waveforms, doesn't expose the ability to set multle input ranges per channel, but there is a quick fix that you can do to be able to add it to the vi. See below:
The block diagram of the AI Acquire waveforms is as follows:
As you can see, the inputs of the vi that are exposed are simply the first element in a array of clusters including the high and low limits per channel. To set the high and low limits for other channels, you need to simply add another element to the array for channels 1, 2, and 3. See below:
Here you can see I simply added one element, you need to add 2 more for your 4 channels. If it turns out that you are using DAQmx and this doesn't apply, please refer to the knowledgebase above for details and an examples on how to set different ranges.
Regards,
Paul C.

AI acquire waveform. maximum readable data

Hello,
For acquiring data from an DC-accelerometer I'm using the 'AI acquire
waveform.VI' to perform this task. I'm scanning for 10 seconds at a sampling
rate of 10.000 S/s. When I'm looking at the amplitude spectrum I find
spectral components below 1 Hz which can't physically be there. (10 seconds,
so df = 0.1 Hz). Is it possible that this has got to do with the acquiring
technique??
Thanx,
Ron@ld

To expand on the previos response, Nyquist Thereom tells us we need to sample at least twice as fast as the signal's frequency to get an accurate sampling and reduce aliasing effects. Aliasing can also be due to noise sources in the environment so using a low-pass filter is still a good idea. Here is a Knowledge Base on aliasing and low-pass filtering:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/68f14e8e26b3d101862569350069e0b9?OpenDocument

AI acquire waveform

For my project, I am using a last year student's VI as reference, but when loading it up, it asks for a "AI Acquire Waveform.VI" which I cannot be found, and there is no "data acquisition" tab under which it is normally found according to the manual, why is this?

Hi AV34,
What versions of LabVIEW/DAQ do you have installed?
If you installed DAQmx 8.0 then the traditional drivers (NI-DAQ) would not have been installed.
You need to install DAQ 7.4.1 or earlier onto your computer to get the traditional DAQ vi's.
They can be found at the following address:
http://digital.ni.com/softlib.nsf/websearch/3dbf3d343476a28f8625709e006a4937
All that said and done.. What aquisition device are you using? (DAQmx might be the beter way to go)
Many Thanx
AdamB
Applications Engineering Team Leader | National Instruments | UK & Ireland

AI acquire waveform. vi update rate

Hello,
I would like to increase the update rate ( which governs how many samples are acquired per second) for the attached vi- AI Acquire Waveform(waveform).vi.
This vi is a built in vi obtainable from Analog Input palette under Measurement I/O.
The update rate preset is 1000 samples per second, i want it to be 10,000 per second.
If i type it manually, it doesnt stay and reverts back to 1000.
I am using LABVIEW 8.6 on Windows XP machine
Thank you very much and Regards
poli
Solved!
Go to Solution.
Attachments:
AI Acquire Waveform (waveform).vi ‏14 KB

Hi Poli
Have you looked at the the daq examples. Labview is shipped with a lot of examples. Also are you running this by using the continuous run button? That button is for debugging only, and it is a no-no to use it for other purposes
If you are new to Labview perhaps some of the online basic lessons will do you good.
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

Comedi read command and acquire waveforms VIs

I am wondering about the implementation of the comedi read command in the VIs I got from the NI site.
One of the VIs is called "acquire waveforms" which calls "comedi read". everything seems to be working fine, but I am very curious about a small part of the comedi read VI.
If you look closely at it, you will see that after reading in the samples using the CIN that just calls read() , there is a formula node that basically asks the VI to save only the first half of the array. I am wondering why this would be so? Does it have to do with the way read() works?
I tried changing the VI so that the all bytes from the read() call are entered into the "data" array. But when I do this, labview gets stuck.
any ideas?

Hello:
This question belongs in the Measurement Hardware Driver Delvelopment Kit (DDK) Forum located here:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=8&RFORMNUMBER=3&RHIDETAG=TRUE&UCATEGORY_0=_321&UCATEGORY_S=0
The Comedi driver set is supported by www.comedi.org but you might get some answers from the DDK Forum as well.
Sincerely,
Brooks B
Applications Engineer

Help with Multi point chart plot hile using the waveform data type..

Currently I have two channels being transfered into the AI C-Scan block (by means of a build array) in hopes to display the outputs on a chart as well as an output file. As an outout I am using the waveform data type, as I hear this is the way to go. Problem is that I have the the Waveform chart directly connected to the waveform out put the the AI C-SCAN block but nothing is being displayed on the chart. Although the time is updated on the chart it is listed as the year 1903. I do have data these channels as the there are digital outputs for these channels. Perhaps I should use the AI CONFIG and AI READ clocks rather than this AI C-SCAN. Any ideas...

Christian,
Please see the Real-Time Chart shipping example for LabVIEW. This example describes how to set the base time of the chart so that the time and date are correct.
You may want to autoscale the Y-axis as your data may be out of range of your chart and that is why nothing is seen.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask

Problems using acquire waveform..​.

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