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

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How to structure the DMA buffer for PXie 6341 DAQ card for analog output with different frequencies on each channel

I'm using the MHDDK for analog out/in with the PXIe 6341 DAQ card.
The examples, e.g. aoex5, show a single Timer (outTimerHelper::loadUI method), but the example shows DMA data loaded with the same vector size.
There is a comment in the outTimerHelper:rogramUpdateCount call which implies that different buffer sizes per channel can be used.
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Does anyone know what the format of the DMA buffer should be for data for multiple channels with different frequencies ?
For example, say we want a0 with a 1Khz Sine wave and a1 with a 1.5Khz sine wave. What does the DMA buffer look like ?
With the same frequency for each channel, the data is interleaved, e.g. (ao0#0, ao1#0; ao0#1, ao1#1, ...), but when the frequencies for each channel is different, what does the buffer look like ?

Hello Kenstern,
The data is always interleaved because each card only has a single timing engine for each subsystem.
For AO you must specify the number of samples that AO will output. You also specify the number of channels. Because there is only one timing engine for AO, each AO will channel will get updated at the same time tick of the update clock. The data will be arranged interleaved exactly as the example shows because each AO channel needs data to output at each tick of the update clock. The data itself can change based on the frequency you want to output.
kenstern wrote:
For example, say we want a0 with a 1Khz Sine wave and a1 with a 1.5Khz sine wave. What does the DMA buffer look like ?
With the same frequency for each channel, the data is interleaved, e.g. (ao0#0, ao1#0; ao0#1, ao1#1, ...), but when the frequencies for each channel is different, what does the buffer look like ?
In your example, you need to come up with an update rate that works for both waveforms (1 KHz and 1.5 KHz sine waves). To get a good representation of a sine wave, you need to update more than 10x as fast as your fastest frequency...I would recommend 100x if possible.
Update Frequency: 150 KHz
Channels: 2
Then you create buffers that include full cycles of each waveform you want to output based on the update frequency. These buffers must also be the same size.
Buffer 1: Contains data for the 1 KHz sine wave, 300 points, 2 sine wave cycles
Buffer 2: Contains data for the 1.5 KHz sine wave, 300 points, 3 sine wave cycles
You then interleave them as before. When the data is run through the ADC, they are outputting different sine waves even though the AO channels are updating at the same rate.

I am using an NI PCI 6024 E board device for an analog output application. Can I generate two independent waveforms, one on each analog output channel?

I am using an NI PCI 6024 E board device for an analog output application. Can I generate two independent waveforms, one on each analog output channel? In attach I send a example of my vi to control one chanel, but i need to control both but with diferent waveforms.
Is the vi correctly programed to this propose?

Yes you should be able to do that. look at the signal generation examples shipped with LabView
You can create a 2 D array, with each row representing a wave form per channel. The number of points of the wave form (per row of the 2 D array) represent the number of points in the output buffer
The wave forms can have different amplitudes/shapes, and therefore they are independent in this sense.
However, you need to set the update rate,which is the same for both channels. The update rate together with number of points per buffer determines the frequency of the wave forms. This means the two wave forms will have the same frequency.
To have different frequencies, you need to have say, on wave form with one cycle per buffer, and the other waveform have 2 cycles
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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
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Finite pulse train with different frequency

Hello,
I'm trying to modify the labview example "generate finite pulse train" to generate a finite pluse train with different frequencies. Each freq will run 400 pulses. The freqs are stored in an array, which is being fed into a for loop. Thus ramp up the freq each iteration. However the program only generate 400 pluse at first given freq. I'm fairly new to daqmx and not sure what is wrong. Anyone have some idea how to fix it?
Attachments:
pulse train finite mod.vi ‏38 KB

The best "fix" will depend a bit on the needs of your app.
Is it ok to have a fraction of a second without any pulses each time you change frequencies? If so, then there's a pretty simple solution:
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3. So for each freq in your array, you'll program the counter for that frequency, start the generation of pulsetrains, and then stop the task after 400 pulses have been generated.
If you must change frequency on-the-fly, producing *exactly* 400 pulses at each freq setpoint will be tricky, and maybe even impossible to do reliably.  Some techniques will get you closer than others though, so post back if you need to do this.
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hi,
I am writing data on the two analog output channels on my PCI-6052E card.But AO write takes only one dimensional array of waveform data. How can I simultaneously output seperate waveforms on each of the analog output channels(say sine on DAC0 and square wave on DAC1)?

I've had a similar experience I believe.
I had to create the two waveforms with function generators, suck out the Y
values, then Interleave them into one array.
Basically, point one was the first point in waveform1 for Dac0, point two
was the first point of the second waveform for Dac1.
Then that gets wired to the output block where you tell it to scan both
channels.
Confusing as labview eh??
"shiv" wrote in message
news:[email protected]..
> hi,
> I am writing data on the two analog output channels on my PCI-6052E
> card.But AO write takes only one dimensional array of waveform data.
> How can I simultaneously output seperate waveforms on each of the
> analog output channels(say sine on DAC0
and square wave on DAC1)?

PC able to detect all except for the analog output channel of my SCB-68 device.

I would like to use the analog output channel of my SCB-68 device. I tried to locate the analog o/p using the wizard but still unable to detect. Why is that so?
Any possible steps/procedure that i have missed out?
Thanks

Rezn,
Aha, therein lies the problem. This was what I suspected, and thus my question as to which data acquisition card you are using. The DAQCard-AI-16XE-50 has analog inputs, digital I/O, but no analog outputs at all. So your card is working as it should, but it has no analog outputs.
If you have the 2002 National Instruments catalog, you can see this in a table on page 231 (your DAQ card is the one on the bottom), or check this pdf file:
http://www.ni.com/pdf/products/us/2mhw254-255e.pdf
Your card is also called the NI6012E. Check out the small table on the first page.
Mark

[svn:bz-trunk] 13716: since include-read-only is a server global setting, we can't have two channels with different value.

Revision: 13716
Revision: 13716
Author:   [email protected]
Date:     2010-01-22 09:26:12 -0800 (Fri, 22 Jan 2010)
Log Message:
since include-read-only is a server global setting, we can't have two channels with different value. remove the test for the include-read-only false. update the service-config.xml as well.
Modified Paths:
    blazeds/trunk/qa/apps/qa-regress/WEB-INF/flex/services-config.mods.xml
    blazeds/trunk/qa/apps/qa-regress/testsuites/mxunit/tests/remotingService/dataTypes/ReadOn lyTest.mxml

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Message Edited by m.lacher on 07-14-2008 07:03 AM

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Attachments:
Single Point Peak Valley Log.vi ‏53 KB

Hi Dennis,
Sorry for that I have modified the VI.
Because the peak and valley of every channel will occur at different time and I want to log the peak/valley with the time stamp.
How can I log them on the same file.
Attachments:
Single Point Peak Valley Log_Mod.vi ‏53 KB

2 analog output channels with different frequencies

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