Optimum sampling freq. in PCI-6220 DAQ

The NI PCI-6220 DAQ has a fixed anti-aliasing filter (called "small signal bandwidth" in the documentation) of 700 KHz. The DAQ itself has a maximum sampling rate of 250 KHz.
Currently, I sample a given signal (which may have lots of interferences) at 256 Hz, and then digitaly filter it and decimate it to get a final sampling rate of 16 Hz. This gives me a signal of a bandwidth up to 8 Hz, which is fine. Thus, I effectively oversample by 16, and then decimate by 16.
I am wondering that, since the anti-aliasing filter is 700 KHz, then I might be better off sampling at a much higher rate, say 200 KHz, and then filter-decimate accordingly. I believe this should give a better performance since the anti-aliasing filter will work best in this case, while if I sample at 256 Hz then I am effectively not benefiting much from it.

Your sampling rate needs to be at least twice as high as the highest frequency interfering signal, so it sounds like >=100 kHz will be needed to meet the Nyquist criterion on all the interference. Any interfering component which is aliased in cannot be removed by filtering or other post processing. So you need to prevent the aliasing.
The 16-bit converter of the 6220 has a theoretical dynamic range of ~96 dB. So to get the best measurement of the interfering signals you want to make sure that the signal is very near the full scale of the selected range.
Even a simple RC antialiasing filter with a time constant of ~10 ms would substantially reduce the higher frequency interference components and make you signal processing much simpler. Why do you not want an external filter?
Lynn

Similar Messages

Quadrature encoder on PCI 6220 DAQ custom digital filter problem

I am using both counters on my 6220 DAQ for quadrature encoders. What I am trying to do is filter some bounce that I am getting on the axes. I want to be able to custom set the minimum pulse width for each encoder (or both the same should be fine). The problem is that the digital filter using DAQmx channel property for each line seems to work fine (I haven't proven that this actually works) but one has to choose from preset values (the smallest being 2.55ms). I want to reject anything that is less the 10ms. This document mentions that you can set up a programmable filter based on an external filter clock. How do you actually do this? Is there no way to use one of the internal timebases for this? If so how? The "Digital Filtering Conciderations for TIO-Based Devices" entry in the NI-DAQmx help states that you can choose one of four different values for a debouncing filter on a PFI line (different values than the previously linked document) and a custom filter value.
OK here is the short question .... is there a way for me to digitally filter the lines coming into my counters to reject anything less then 10ms through software only? If so, how? If using an external timebase is required, how do I do this?
Thanks in advance for any help
Greycat

Hi Greycat,
Although the documentation does mention that you can have one programmable filter setting, this is only true for TIO-Based devices. Unfortunately, the NI-6220 is a M-Series, which means that the only allowable minimum pulse widths settings are 125 ns, 6.425 µs and 2.55 ms. More information on this can be found in your NI-DAQmx help under NI-DAQmx Device Considerations » Digital Filtering » C and M Series.
I believe for your application requirement, we would have to look into some oour Counter/Timer devices.
S_Hong
National Instruments
Applications Engineer

What is the maximum number of samples that can be acquired with a single trigger using PCI-6036E DAQ card?

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

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

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 Kienig

Since 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

PCI-6220 COUNTER (Labview): Does "Sample Source" = "Gate Source"?

Hello,
I'm using Labview, DAQmx, PCI-6220 (Counter0). I connected an incremental encoder signal to the source input of CTR0. In Labview, the "DAQmx Timing" vi requires that the "source" input be wired. Does this "source" actually mean the source of the sample clock vs. the "Source" input to the counter?
Thanks for your assistance,
Chris

Chris,
When you talk about using a DAQmx Timing vi, I assume that you are performing
buffered event counting or any other task that performs buffered acquistion.
You can see an example that performs buffered event counting in NI Example
Finder called Count Digital Events Buffered - Continuous. The DAQmx
Timing vi in this example is used to read the current state of the counter
into memory at a constant rate. The source input of the Timing vi in this
case means the source of the sample clock. This clock is what determines
when the counter state is read and stored into a buffer.
If you are performing event counting, and do not need buffered acquisition (no
sample clock), you can look at example Count Digital Events.vi in Example
Finder. In this example no DAQmx timing vi is used.
Regards,
Jesse O.
Application Engineering
National Instruments
Jesse O. | National Instruments R&D

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]

Trouble Acquiring Digital Input through 1302- 1180- 1349-PCI 6220- software

Hi,
I've got an SCXI-1000 chasis, and I'm trying to use an external clock and trigger signal to acquire data from a BNC 2095 board. I have the 1302 unit to input my external digital signals. The information feeds through the following units: 1180--> 1349 --> SHC 6868 EPM cable --> PCI 6220 card --> software
I've got my trigger connected to terminals 39(+) and 24(-) in the 1302 unit. The external clock is connected to terminals 38(+) and 33(-).
Within the DAQ Assistant, I've selected the trigger as PFI 1 and the clock as PFI 0.
I'd like to test the setup, but the test panel in the MAX won't let me select PFI0 or PFI0 as a channel. I've also got a acquisition VI made, but it doesn't log any data even though there are no errors. That's why I want to check that I'm getting the trigger/clock signals properly.
Any ideas on what to check or change?
Thanks,
Michael

Hi Michael,
In general, it's not a good idea to call the DAQ Assistant in a loop, since it allocates and frees resources every time it runs. You might want to take a look at the DAQmx examples in the NI Example Finder (Help>>Find Examples). There are located in the Hardware Input and Output\DAQmx directory in the Example Finder. There are several examples, with several timing and triggering configurations.
Here is some information about reference triggers: In NI-DAQmx, the stop trigger is referred to as a reference trigger. The reference trigger establishes the reference point in a set of input samples. It allows you to acquire samples both before and after the trigger is received. The number of pretrigger samples to be acquired is set using the Pretrigger Samples input. The number of posttrigger samples to be acquired is automatically determined by subtracting the number of Pretrigger Samples specified from the number of Samples to Read specified.
Also, take a look at the article I am linking below for information about NI-DAQmx. I hope all of this helps!
Learn 10 Functions in NI-DAQmx and Solve 80% of Data Acquisition Applications
Michael P
National Instruments

How can I set up a delayed analog trigger on PCI 6115 DAQ

I have an S-Series PCI 6115 DAQ which I’m running with Labview. I’m using it to measure signals from an acoustic emission sensor and two force transducers. I’d like to set up a delayed analog trigger which will start acquisition on all three channels a period of time after a selected channel’s voltage exceeds a threshold.
Currently I’m using the AI Config VI in line with the AI Start VI and AI Read VI to capture data after a analog hardware trigger occurs. A software trigger probably wouldn't work because I have to sample my data at 10MS/sec. My setup works fine for triggering without any delay or skip counts. However, if I set the delay or skip count in the additional trigger parameter field of the AI start VI, there is no effect, and the device still starts capturing data immediately after the trigger is received. What is the cause of this, and how can I get around it?
Also, is it possible to sample the channels of a PCI-6115 DAQ at different rates? Right now, I’m sampling all my channels at 10MS/sec and throwing away data on all channels except one. However, this seems relatively slow and eventually I would like to attempt pseudo-real time control using my data.

rpursley8 is right about needing to get the counters involved if you want a hardware timed delay in your application.
Concerning whether or not you can sample at different rate, check this document out.
Sampling Different Channels at Different Rates with NI-DAQmx
Otis
Training and Certification
Product Support Engineer
National Instruments

PCI-6220 Analog output to Biometrics DataLOG?

Hello all,
I am trying to send an analog signal to our Biometrics DataLOG device. Currently, I have the PCI-6220 card installed and am running the signals through a BNC-2111 DAQ. I am getting no output from our card through our DAQ, any suggestions? Thank you!

Provide some detailed information. How is the 6220 configured? How is it wired to the bnc? Do you see an output when you test the device in MAX? Are you checking the output with a meter or a scope or are you just relying on this unknown (to most of us) logger?

Help PCI 6220

Hello I have a final project study on the design of a tester and I want to develop the program on the LabWindows / CVI for the PCI 6220 National Instruments if you help me thank you

Hello,
Maybe you should explain more precisely the functionnalities required for your tester.
Beyond that, you can find many DAQ examples in CVI...

DAQmxbase with pci 6220

I have developed C code to sample a USB-9215A using nidaqmxbase on windows xp. Installing only nidaqmxbase (not nidaqmx) the code ran well. Now on the same machine I have installed a PCI-6220 card and am trying to reuse the same code (for both devices Dev1, Dev2). After trying many different strategies it is not working and the USB device no longer works either. Sequence of events:
1) There did not appear to be a driver for the 6220 using nidaqmxbase
2) So removed nidaqmxbase and installed nidaqmx (940f1) , the device is now found (Usb on Dev1 and PCI on Dev2)
3) Tried to compile the code but it appears nidaqmxbase is not a subset of nidaqmx as indicated in the documentation (e.g. calls to "DAQmxBase****" functions are not found when linking against NIDAQmx.lib) and code will not compile
4) So reinstalled nidaqmxbase (345) over the top of nidaqmx, code now compiles (linking against nidaqmxbase.lib) but will not run (for either USB or PCI)
5) Error is DAQmxBase Error: 2288296
6) The devices do not appear to be available to nidaqmxbase e.g. program "lsdaq" does not show devices
So the question is do I need to ditch the nidaqmxbase software and re-write it using nidaqmx functions or can nidaqmxbase be made to work with the pci-6220 (my preference)

Solution found
It seems that 6220 is not supported in nidaqmxbase, so removed all ni software and installed nidaqmx only
Then the code can easily be ported by changing all DAQmxBase**** function calls to DAQmx***** function calls

Problems with PCI-6220

Hi Labviewers,
I'm using a a PCI 6220 card for AI and having some troubles (LabView 7.0 / XP on industrial PC / DAQ-mx 7.4 but I also tried with other versions).
1) the card is not "plug'n'played", at least not completely; it's recognised as a NI card, but with no model: I need to reinstall the driver and let XP to search automatically the correct driver to have it working
2) my program works well if manually launched, but doesn't acquire data when launched at Startup; in this last case, after the program is closed, MAX is not able to access the card (it cannot even reset it!), moreover, restarting/switching off the PC does not help: the only way to get the card working again is to completely uninstall the driver and reloading it!
I found a workaround, though: keeping the program into the Startup folder, I delayed launching by some seconds.
Has anyone seen something similar?
Paolo
Paolo
LV 7.0, 7.1, 8.0.1, 2011

I think you found the answer yourself by delaying the startup of your application.
1) my suggestion is to always use the latest Driver. NIDAQmx 8.1 is out and available for free download.
2) There might be something related to your specific HW that shows this behaviour. Basically, the driver is loading up sometime after the app has started. This means that when the DAQmx functions are called, the driver has not yet gotten hold of the PCI-6220.
Try and change the PCI Slot for the card and see what happens. Anyways, adding a few seconds of delay at the beginning of your application may just do the trick.
3) Also, did you check if your PCI bus is supplying 3.3 V as well as 5V on the rails?
AlessioD

PCI-6220 and Absolute Encoder

Hi,
Can anyone point me to a C# compatible example that would serve as a good starting place for determine the position of an UUT?
Using 12-bit absolute encoder with PCI-6220, I need to determine if the UUT (with optical encoder mounted) is moved either up/down 30 degrees from 0.
This piece of code will be called from another API to tell the motor to move then stop moving when the desired position of the UUT is found.
Any advice would be appreciated.
Sonny

Hi nimaq,
If you are using the DAQmx drivers, you can find the .NET examples here:
C:\Documents and Settings\All Users\Documents\National Instruments\NI-DAQ\Examples\DotNET2.0\
The position measurement example is located here:
C:\Documents and Settings\All Users\Documents\National Instruments\NI-DAQ\Examples\DotNET2.0\Counter\Measure Position
Chris Bolin
LabVIEW Partner Program, CLA

PCI 6220 digital I/O CB68LPR

Hi,
I would like to know how to connect the PCI 6220 with CB68LPR for digital input and output? appreciate your answers.
regards,
nazreen

Hello Nazreen,
You can use the SHC68-68-EPM 68 Pin Shielded Cable (part #: 192061-01) to connect your PCI 6220 to the CB-68LPR.
The CB-68LPR connector block has 68 pins labelled "J0" through
"J67". These pins have a one-to-one correspondance with the 68
pins of your PCI 6220, i.e. pin "J5" of the CB-68LPR correspondes to pin 5 of the PCI 6220. From looking at the M-Series Help
manual under 'IO Connectors and Pinouts'', you can find what pins
correspond to what actual signals on your DAQ device. The PCI
6220 has three ports (groups of 8 lines) available for digital
I/O. I can see from the pinout diagram for the 6220, that port 0
line 0 (P0.0) corresponds to pin 52, or terminal "J52" on the
CB-68LPR. I hope this helps!
Travis G.
Applications Engineering
Message Edited by Travis G. on 04-05-2006 04:54 PM

Optimum sampling freq. in PCI-6220 DAQ

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