VI Logger - use of multiple DAQ cards

How do I configure VI Logger to acquire data from multiple DAQ cards?
I have set up channels for two DAQ cards but the VI Logger Tasks seems only capable of acquiring from either DAQ card, not both.

Hi Metronet,
VI Logger doesn't support acquiring data from multiple DAQ cards.
VI Logger was a free software tool that came with new DAQ cards up until the end of March. To get customers up and running and acquiring data in the quickest possible time.
VI Logger however is not LabVIEW, and as such cannot use more than 1 DAQ card at any one time. If you want to acquire from multiple cards then you will need to program in LabVIEW, CVI, Visual Basic or Visual C.
I am sorry that I have to inform you of this, but NI has no plans to release VI Logger with support for multiple DAQ cards.
Regards
James
Applications Engineer
NI UK

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How to use PXI 6071E daq card to complete multichannels scan with high sampling speed

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Attachments:
多通道监测4.vi ‏199 KB

Sunny;
As you are scanning multiple channels and the signal range is high, you can try to set the interchannel delay a little higher. The interchannel delay is the time which the multiplexer will take to switch to the next channel. If that time is to short, the instrumentation amplifier can have problems to settle, and then an error at the reading will happen.
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Hello,
You won't need any other functions after AI_Read_Scan or after DIG_In_Prt since both functions are for none buffered acquisitions.
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Hello;
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Hello, I am trying to access two analog-input cards in a "ping-pong" type fashion with LabVIEW 7.1.
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"Error -200558 occurred at DAQmx Create Channel (AI-Voltage-Basic).vi.
Possible reason(s):
One task cannot contain multiple independent devices.
Create one task for each independent device.
Device: B
Device: C"
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Attachments:
Surrogate.vi ‏251 KB

One task cannot span multiple devices. Your problem is that your physical channels in DAQmx Create Channel reference two different devices. You cannot create tasks like that. If you want to ping pong between devices, you'll have to do it with single point reads like this:
B/ai0 >> DAQmx Read Single Channel Single Sample
C/ai1 >> DAQmx Read Single Channel Single Sample
etc...
Hope this helps.
Regards,
Erin

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Giri,
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I hope this information is helpful.
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Applications Engineer
National Instruments

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AI using two PCMCIA DAQ Cards

Can anyone tell me the easiest way to do analog input data acquisition
(in LabVIEW) using two PCMCIA (DAQCard-AI-16E-4) cards? There is no
RTSI bus connection between the cards... as would typically be used to
synchronize the scan/trigger.

[posted and mailed]
[email protected] (Joshua Marshall) wrote in
<[email protected]>:
>Can anyone tell me the easiest way to do analog input data acquisition
>(in LabVIEW) using two PCMCIA (DAQCard-AI-16E-4) cards? There is no
>RTSI bus connection between the cards... as would typically be used to
>synchronize the scan/trigger.
>
I'm not sure about these particular cards and whether it applies to them
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commence when the signal is triggered through one of yo
ur channels. Set up
two parallel processes (one for each card) and have two conditional
acquisitions. Combine the data in some fashion (depending on what you're
after).
This would be the simplest, but there are probably other more efficient
ways of doing it.
cheers, Alex.
Alexander C. Le Dain, PhD
ICON Technologies Pty Ltd
http://www.icon-tech.com.au

Measuring the frequency using PCI 6221 Daq card

Hi
I want to find the frequency of an external signal.
How can i do that give me some idea or example.
Regards,
Hari

If you need to capture the waveform look at the aquire waveform examples and add the
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Owning Palette: Waveform Measurements
VIs
Requires: Full Development System
Takes a signal in, finds the single tone with the highest
amplitude or searches a specified frequency range, and returns the single tone
frequency, amplitude, and phase. The input signal can be real or complex and
single-channel or multichannel. Wire data to the time signal in
input to determine the polymorphic instance to use or manually select the
instance.
(copied from the help)
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

I am trying to sample 2khz signal at 8khz,with an accuracy upto 6place of decimal ,using pci 1200 DAQ card.

how can i externally trigger this operation.i need to sample my signal at 4 points and store it in a excel sheet and the values should be same,as the the 2khz signal and the 8 khz signal both are comming from the same source.

could u tell me what more details would be required....i will be more than glad to let u know about it.

Capturing data instantaneously after condition is met using 2 DAQ cards

Hi all,
I am wanting to sample a pulse and a sine wave at a low frequency of 1 kHz point by point sampling and upon a condition being met - the leading edge of the pulse being greater than a certain value - I the want to take a certain number (here 270) of samples of the sine wave at 50 kHz, multiple samples. I am doing this within a case structure and using a separate DAQ card.
The problem is that when the conditon is met is does not capture the data at the higher frequency straight away. It misses part of the sine wave before commencing capturing the 'window' of the 270 samples of the sine wave at 50 kHz. I want to know if there is any way of speeding this up? I am aware that using an FPGA could help but I don't have access to one.
The other solution would to advance the condition, i.e advance the pulse train by a certain amount so that I compensate for the delay in activating the high freq capture. I would need to set up this advance of the pulse train so that, after the delay in activation, it captures the data exactly where it is required to. What would be the best way to do this? I could delay the pulse train by a certain number of samples/ or delay the sine wave, or I have read that you can use the sample timer/counter within the DAQ card to change the 'trigger of the pulse train'. How would I implement this?
Attached is my vi. I would be very appreciative if you could help.
Attachments:
2 DAQ cards Low and High Freq Sampling.vi ‏29 KB

I do not have DAQmx or any suitable DAQ devices so I have not tested this.
This is a start on cleaning and speeding things up. Note that writing to the front panel indicators at 1 kHz will not work because the screen update rate is on the order of 50-100 Hz. Also charts take a considerable amount of computation beacuse they need to (1) store data in the internal buffer, (2) erase old data if the buffer is full, and (3) (slowest) recalculate all the pixels in the display for the updated data. The cart should be moved to the parallel loop. The condition True boolean will only be true for about 5 ms out of each 100. Look at the 5 ms boolean.vi attached. It runs close to 1 ms per iteration. The boolean is true about 5% of the time but I never see it change. Remove that boolean from your VI.
With continuous sampling on the pulse channel and reading 1 sample every millisecond (assuming you get that fast) when the high speed sampling occurs it takes 5.4 ms to acquire the 270 high speed samples. So, ten times per second the loop takes >= 6.4 ms for an iteration. The next sample it reads from the pulse channel is the one which was measured (acquired) at 1 ms after the previous sample. Thus, this data point is read ~5.4 ms after it actually occurred. The next time you detect a pulse, it will be 5.4 ms late. The second one will be 10.8 ms late. Eventually you will get a buffer overflow, but your data will be useless long before the error occurs.
The Dual Sampler Simulator.vi shows a possible approach to the issue. It simulates sampling both channels at high speed. I generate both a sine wave and a square wave and sample both at 50 kHz. It simulates reading 4000 samples at a time (equivalent to reading 12.5 times per second or every 80 ms). The square samples are then processed for the transition using the boolean Implies function. I do not recall whether the Conditional terminal was available in LV2012. I did not get an error when saving for previous version so I think it will be OK. The same thing can be done with a while loop with some extra logic. This does not handle the case where the transition occurs at the boundaries of the 4000 sample segment. To handle those cases use a shift register on the outer loop to pass the needed samples to the next iteration. The 800 ms Wait makes it run slower than "real" time but allows you to see what is happening.
Lynn
Attachments:
2 DAQ cards Low and High Freq Sampling.2.vi ‏26 KB
5 ms boolean.vi ‏10 KB
Dual sampler simulator.vi ‏15 KB

VI Logger - use of multiple DAQ cards

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