Low sample-rate measurements on the PCI-6115 DAQ card
I need to measure an analog signal at a sampling rate of a few tens to hundreds of Hz in sync with the rising edge of an external clock. I have a PCI-6115 DAQ card w/ Labview 6.1 and NI-DAQ 6.9.2. The PCI-6115 is a high speed card and has a minimum sample rate of 10 KS/s. Is there any way of implementing a low sampling rate measurement using the PCI-6115 in sync with an external clock?
Thanks in advance.
Kuldeep,
It is possible to do what you are describing above (in fact I don't think an external clock is required to do this), however, bear in mind that the reason for this minimum sampling frequency is due to the ADCs used on this high speed board. The ADCs used are pipelined ADCs, meaning that when a signal is digitized, it is digitized in distinct stages within the ADC (in the case of the 6115, I think there are 3 stages involved). Data is moved from one stage of the ADC to the next each time a sample clock pulse is recieved. If too much time elapses between these clock edges, the signal to be digitized can actually 'leak' off of the ADC. This can result in improper digitization, which can lead to less accurate measurements. So, while it is possible to mak
e the device sample below it's minimum rate, it may be advisable to sample faster than the rates required by your application, and either average multiple data points per measurement, or throw away extra points taken.
I hope this helps,
Dan
Similar Messages
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I m using the 404A force transducer unit by Aurora Scientific and i want to connect the (converted to Volt) output, which is a BNC cable, to the PCI-6036E DAQ card via the SCB-68 connector block, facing difficulties in choosing the correct input mode for my signal(couldn t clear this using the manual), setting the switches and which channel shall i use in the block connector in order to configure ot with LABVIEW
Hi MSc Student,
Connecting your transducer to the 6036E card via the SCB-68 connector block should be pretty straight forward. You have 2 choices of input mode, Referenced Single Ended (RSE) this is where you will connect the screen of the BNC cable to a ground connection for the DAQ card in the SCB-68 and the other to any analogue input channel . These are listed in the device pinouts in the help section of MAX, under the 68 pin devices section. The terminal block numbers correspond to the DAQ card's pin numbers. Another method, which avoids ground loop problems would be to use the Differential connection and connect the signal and ground connections of the BNC cable to a differential analogue input, these are listed in the 6036E manual and in th
e MAX help section again. the disadvantage to using this method is 2 analogue input channels are used and you must use the lowest 8 analogue input channels for differential inputs.
The switch settings that you need can be found in the manual for the SCB-68 in table 2-1, the manual can be found here : http://www.ni.com/pdf/manuals/320745b.pdf
The switches are for power to extra signal conditioning and the cold junction compensation for thermocouples which in your case you do not need so set the switches to the positions in the first box ie Direct feedthrough, with temperature sensor disabled and accessory power disabled. The channel you use should not matter the only ting to remember will be that if you use differential mode measurement that you will be connecting the signals to AI(n) and AI(n+8) so differential input 0 is across the connectors for AI0 and AI(8). The channel numbers corespond to the analogue input number for the card.
I hope this information helps,
Chris M
App
lications Engineer, National Instruments -
How does the PCI-6229 DAQ-card communicate with CB-68LP connector block?
Hello!
I want to do a very simple task which is to just turn on/off a LED. I am using LabVIEW 7.1 and I have a DAQ-card PCI-6229. The DAQ-card is then wired to a connector block CB-68LP.
Now my problem is to figure out how the connector block communicates with the DAQ-card?
In the file I attached there is a picture of connector block and the device pinouts from the DAQ-card. But how do I know which of pinouts triggers some connector on the connectorblock?
Which are digital outputs on the DAQ-card?
Where can I read about this?
Attachments:
daqANDconnectorblock.bmp 2437 KBHello asc01001:
The digital pins of the PCI-6229 are labelled as Px.y, where x is the port name while y is the channel name. For example, pin52 of the NI 6229 is P0.0; which is also port 0, channel 0 of the digital I/O of the DAQ card.
While "D GND", which are located at pin53, pin18, pin50, etc. are the negative terminal of all digital I/O of the DAQ cards.
Please advice if this helps. -
What 's the meaning of "sample rate =-1" when to use the CAN init.vi?
ALL,
I saw a kind of use to CAN init.vi where The mode = "output recent" and the sample rate = -1. I check the NI CAN help document, it seems that the sample rate must be large than 0 when the mode = output recent. So,here,why the sample rate can be -1? What does it mean?
Thanks!
LaiI found that it is different whether to use "-1" or ''0" to sample rate. In CAN init.vi, there is an input parameter filepath which is used to load the ncd file or dbc file. The ncd file can't set the sample rate of CAN message, but dbc file can. When I use sample rate = -1 and dbc file , the period(=1/sample rate) of CAN transmission equals the Sample time defined in dbc file and is not determined by loop time in LabVIEW programm. But when I use sample rate = 0, the period of CAN transmission equals the loop time in LabVIEW programm. So I guess the period of CAN transmission is determined by the Sample time defined in dbc file when use sample rate = -1. Is that true?
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1. My PCI-6036E card has a FIFO of 1024 bytes in AI. Maximum how many samples can be acquired with single trigger for digitizing a waveform?
2. PCI-6036E DAQ card has got a AO with 10ks/s update rate? Can I generate a pulsed output with the AO of this card? I need a pulse of, say, 5 V and 1 kHz frequency.Giri,
1.The trigger is usually for enabling the acquisition. I mean, when it is logic zero, you acquire nothing; however, when it is logic one, you start acquiring your waveform,and you can acquire continuously without having to worry about how many samples, unless you want to set your program for doing so. You can acquire continuously by implementing buffer acquisition. Finally, the FIFO that is in the board will not affect the buffer acquisition.
2.Yes, you can do that! You can generate your 5V signal with that specific frequency, and you should not have any problems, because the freq fits in the update rate.
I hope this information is helpful.
L Aguila
Applications Engineer
National Instruments -
PCI-6023E DAQ card maximum sampling frequency
Hello
I am using PCI-6023E DAQ card in pc-based ETS solution (and writing appilication in LabView 7.1 with RT module). The card has 200kS/s maximum sampling frequency, but it can be set for much higher sampling frequencies and the waveform acquired appears to be correct (i.e. i've tried setting it fo 1MS/s and sampling 400kHz sine, which is obviously above Nyquist frequency for 200kS/s card, but on spectral graph, main peak is at 400kHz). Is the card driver doing some kind of free/coherent sampling?
Moreover, when sampling frequency is set to 200kS/s, the card seems to be doing same thing - i.e. for 200kS/s and sample block size of 200kS, graph should be updated once in a second, but it's updating slighty slower.
I'd really appreciate if someone could explain me (or gave me a link to materials) what exactly is happening here? Is driver doing some background work, or maybe it is problem with network latency/unstability ? What is the impact of this effect on real-time aquisition?
Thanks in advance
Jan KienigSince the fundemental is 4 times the nyquist, then what you are measuring is an alias of the fundemental. This works well as long as the fundemental is a repetitive signal. Sampling every other peak and every other node looks the same as sampling every peak and node. Tektronix exploited this on their 7S series sampling heads. Another use of this phenomena is the effective demodulation of high frequency signals as long as the bandwidth meets nyquist. As with your card, if the input amplifier supported it, I could extract modulation information from a 500 MHz signal so long as the the bandwith of that modulation did not exceed 100 kHz.
Parker -
FS: PCI-6024E DAQ card for sale - 200,000 samples/sec - 16 inputs - GREAT DEAL!
Hello everyone,
I have a PCI-6024E DAQ card for sale.
If you want more information, please contact me - I have the following items, selling as a set:
* PCI-6024E Multi I/O and PCI DAQ card, low-Cost E Series Multifunction DAQ, 12-Bit, 200 kS/s, 16 Analog Inputs ($595/list)
Thanks,
Dave M
[email protected]I'm sorry, I should have put in the post that I will entertain offers. Please make an offer.
Regards,
Dave M.
"DaveM" wrote in message news:RJErb.7470$[email protected]..
> Hello everyone,
>
> I have a PCI-6024E DAQ card for sale.
>
> I am sorry if this is off topic - if someone knows what forum to sell NI hardware please let me know.
>
> If you want more information, please contact me - I have the following items, selling as a set:
>
> * PCI-6024E Multi I/O and PCI DAQ card, low-Cost E Series Multifunction DAQ, 12-Bit, 200 kS/s, 16 Analog Inputs ($595/list)
>
> * CB-68LPR (184700B) connector block ($95/list)
>
> * 182482A-01 type R6868 1meter cable ($40/list)
>
> Thanks,
>
> Dave M
> [email protected] -
How do i generate the TTL pulse from PCI 6024E DAQ card
Hi, I'm trying to write a program which generates a single TTL pulse when it is run. My goal is to generate the pulse, send it to the output channel of my PCI 6024E DAQ card, and then use a BNC cable, to display the signal on the oscilloscope. I have written the code and I think it appears fine but when I try to view the signal on the scope I am unable to see the pulse. I have tried slowing down the sweep on the scope and have adjusted the voltage and time scales but have not seen any response. After examing my DAQ card, I noticed that none of the PFI/TRIG terminals on the card are wired; the output channel connects to terminals for DAC0OUT and Ground. I'm wondering if this pin needs to be wired in orde
r to generate the pulse since PFI0/TRIG1 is the start trigger terminal. Any help would be appreciated. Thanks.
Attachments:
ttl.vi 26 KBHi,
You are looking for a retriggerable pulse generation. Please check the Generate Retriggerable Pulse (DAQ-STC).vi example that ships with LabVIEW.
Regards,
RamziH. -
Im using a pci-6221 daq-card.I want to know the difference(use)of a line output and a port output.
Im using a pci-6221 daq-card.I want to know the difference(use)of a line output and a port output.
Hello Hellraiser24,
This question has actually been discussed in another thread here:
http://forums.ni.com/ni/board/message?board.id=170&message.id=95895&requireLogin=False
I hope this helps,
E.Lee
Eric
DE For Life! -
Dear Friends,
I need to interface SCC-TC02 with help of SC 2345 and PCI-6024E DAQ Card.But i can not understand example program.please send me the procedure to interface these three componnets and if possible send me the program.
With Regards,
Eswaramoorthy K Vnce of nth triggering pulse. i need to know when the when the ist trigger occurs and when the nth trigger occurs . please tell me how to to . what i know is that event triggering has to be done with start and stop trigger. please tell me how it has to doneSuresh;
What you will need to do is to set up a digital start and stop triggered Analog Input acquisition. Then you will need to have a counter set as event counter, having the specific number of pulses you need configured as the preset value, configured to count down, and generating a pulse after the terminal count has been reached. That counter output will be the stop trigger of the Analog Input operation. In summary, you will have the external pulse being both the digital trigger of the Analog Input operation and the source pin of the counter, and the counter output being the digital stop signal for the analog input.
I'm attaching a Labview VI that does the start and stop analog input acquisition. You will need to include the counter part and set the stop s
ignal to be the counter output.
Hope this helps.
Filipe
Attachments:
AI_Start-Stop_D-Trig.zip 25 KB -
What is the default gate frequency for the PCI-6602 DAQ?
What is the default gate frequency and default source frequency of the PCI-6602 DAQ?
Hi coachcalamai,
The default behavior on the gate is as if there was no signal on the gate (ungated). If you want a trigger or to send a signal, you will specifically have to set it.
The default signal on the source is the 20MHz internal reference.
Anyway, hope that helps. Have a good day.
Ron -
Counter Problem at low sampling rate
What I am trying to do is to count the input from the camera and generate the number of pulses depending on the delay and interval. At the rate of 33ms the program works perfectly but if the sampling rate is 150ms it generates 2 pulses at a time. Is there a better solution to my problem ? Am I doing anything wrong ? Is it a problem with the loop timing or acquisition timing? I have attached the program. What puzzles me is that it doesnt work if the rate is lower! Please HELP.
Thanks
p.s. I am very new to LabView so please excuse my ignorance.
Attachments:
CoolSnap.vi 142 KBHello sha33,
Thank you for getting back to me with more information. After looking through your code once more, I believe I have found the issue. Since this application is timed entirely in software, it is based on how quickly your operating system can run the program, and thus cycle through loop iterations. Since you have no Timing VIs in the program, this loop is running as fast as possible. Now, in the 33 ms case, you are getting a TTL edge a lot faster, so the DAQ assistant is updating its count faster as well. Lets say hypothetically that your loop is iterating at 60 ms. This means that every time you run through the loop your DAQ assistant will read the updated count value, and since you are counting every 33 ms, your count value will have updated.
Now let's look at your 150 ms TTL signal. This is significantly longer than the 33 ms signal in the previous case. Lets say hypothetically your loop is running on average at 60 ms again. This time, your edge will come in and the counter will increment, generating a pulse with the second DAQ assistant accordingly. Now your loop will run through again 60 ms later but your next edge on the 150 ms signal is still around 80-90 ms away. This means that your DAQ assistant will return the same count value as the last iteration, and once again a pulse will be generated.
Obviously the numbers I used for the loop iteration timing are hypothetical and entirely dependent on the operating system and its resources (i.e. it will run slower with an MP3 or Movie playing in the background). My suggestion would be to use a timing VI such as Wait Until Next ms Multiple to clock your loops more consistently. The goal would be to make sure that your loop is repeating faster than your counter is updating. Alternatively, you could account for the possibility of no counter input in your overall application to prevent a false positive.
Let me know if I can clarify any of the above information, or if you have any additional questions related to this issue.
Regards,
Chris Behnke
Sr. RF Engineer
High Frequency Measurements -
Lossless to lower sampling rate automatic?
I use Apple lossless for many of my imported songs. Will the iPod touch offer to lower the sampling rate on the fly? My shuffle used to do this.
Okay, I tried to bite the bullet and include lossless ripped music files in a synch. I did a SmartPlaylist and limited it to 10GB taken from my general Music Playlist, not played in 90 days. It is now synching a little over 5.6GB in lossless and the rest of the 10GB 128/256. All told 1,235 songs.
It is taking forever to sych. Pardon the pun, but this just about rips it I've got to downgrade the my lossless library which comes from CD's I own. I'm reducing the lossless files now. Hope this works without mucking up the sound too much.
Apple, please add the automatic conversion to a small file via iTunes like my iShuffle!!! Otherwise I've got to manage two music libraries. Any other Apple Lossless Touch users out there? -
Is it possible to adjust the sample rate lower than the default when attempting to record an audio source?
44.1 is the lowest sample rate to record audio at in Logic. But put a Bit crusher plugin on the track and change the resolution there for more lo-fi sounds.
JG -
Low sample rate with NI USB-6008
Hello,
We are working on a project collecting data from a hybrid rocket motor for
University research. We are using a NI USB-6008, which has a sample rate of
10kHz. We are using 3 channels and getting a sample rate of ~60 samples per
second. I have attached the VI. Is this slowed by software, or physical
computer computation speed? This sample rate needs to be much higher. Any help
is greatly appreciated.
- Theo
Attachments:
Hybrid DAQ_10.vi 73 KBHi Rocket 154,
You’ve already had some
great responses, but I just wanted to add a little bit. A great starting point
to writing good code would be the Getting Started with NI-DAQmx: Main Page,
as well as the shipping examples (In LabVIEW, Help » Find Examples) already
mentioned.
If you navigate a bit
through the links (Basic Programming with NI-DAQmx » Getting Started with NI-DAQmx
Programming in LabVIEW) you’ll end up with some great resources. I recommend Learn
10 Functions in NI-DAQmx and Handle 80% of your Data Acquisition Applications.
It will detail many of the functions you can use and give you a feel for proper
code style in LabVIEW.
I hope that helps.
Mark E.
Precision DC Product Support Engineer
National Instruments
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