Labview myRIO Analog data sampling rate

I have been using the myRIO to acquire audio input from a microphone.
In LabView I'm using the Analog Input Express VI to acquire the data.
I wanted to know if there was a way to increase the sampling rate of this data from this VI, or any VI at that?
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Hi ykhali,
Try putting the VI into a timed loop and set the loop rate to your sampling rate.
Regards,
Joel I.
Applications Engineer
National Instruments

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What sample rate does the 2 channel oscilloscope example (solution wizards labview 5.1 ) acquire data at?

I am using labview 5.1 and a DAQCard1200. I chose the Solutions Wizard from the LabView starting window. I followed the steps and selected a DAQ based 2 channel oscilloscope. I chose to program scales etc. myself rather than use the virtual channels. My question is, in this program, when I change the timebase, am I changing the sampling rate? What is the sampling rate for that matter? Is it set to the DAQCard maximum? Does it change if I only set one channel to be active? I threw in some code so that I could take a snapshot of the data, but I end up with 2 columns of voltage data but no idea what the sampling rate was. Makes it very difficult to perform any frequency
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Hi, here's a simple program i did a few years ago. Just remember the daq cards only go up to about 100khz(assuming they have'nt changed) max sampling frequency, so your highest frequency will be 50khz to stop aliasing. This proram will let u select your sampling rate and let u select the number of scans to be aquired. I do not know if the spectrum analyzer side will be any use to u, but its there if u need it.
Stu
Attachments:
op_amp_2.vi ‏104 KB

Conflict between the saved data and the sampling rate and samples to read using PXI 6070e

Hello, I am using PXI 6070e to read an analog voltage. I was sampling at 6.6 MHz and the samples to read were 10. So, that means it should sample 10 points every 1.5 um. The x-axis of the graph on the control panel was showing ns and us scale, which I think because of the fast sampling and acquiring data. I use "write to measurement file" block to save the data. However, the data was saved every 0.4 second and as 35 points data at the beginning of each cycle (e.g. 35 points at 0.4 sec and 35 at 0.8 sec, and so on) and there was no data in between. Can anyone help me how there are 35 reading points every cycle? I could not find the relation between the sampling rate and samples to read, to 35 points every 0.4 second!
Another thing, do I need to add a filter after acquiring the data (after the DAQ assistant block)? Is there anti-aliasing filter is built in PXI 6070e?
Thanks for the help in advance,
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I'm not seeing anything that points to this issue. Your DAQ is set to continuous acquire. I'm not sure if this is really what you want because your DAQ buffer will keep overwriting. You probably just want to set to Read N Samples.
I'm not a fan of using the express VIs. And since you are writing to a TDMS file, I would use the Stream to TDMS option in DAQmx. If you use the LabVIEW Example Finder, search for "TDMS Log" for a list of some good examples.
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How to acquire data from 2 chs of the same DAQ card at different sampling rate

I am using single DAQ card (either 6013 or 6014) in my system i want to acquire data from 2 (or more) channels with following requirements
1. sampling rate of each channel should be independant of each other (say one is 20 Hz and other is 15 kHz)
2. data from all the channels should be acquired simultaneously.
3. coding must be done using DAQmx VIs
I have tried out following things
1. I created separate task for each channel: i found out that two tasks can not run simultaneously even though the channels are different
2. I tried out single task with two channels included in it. and i used 'channels to Read' property to determine from which ch. i want to acquire data: this method works fine if the sampling rates are same. but if i change the sampling rate of one channel it gets reflected in other channels as well.
can somebody help me out to solve this problem.
i will appreciate if somebody can post the sample code as my deadline is approaching
Tushar Jambhekar
[email protected]
Jambhekar Automation Solutions
LabVIEW Consultancy, LabVIEW Training
Rent a LabVIEW Developer, My Blog

Hi Dennis Knutson
Thanks for your suggestion.
Tushar Jambhekar
[email protected]
Jambhekar Automation Solutions
LabVIEW Consultancy, LabVIEW Training
Rent a LabVIEW Developer, My Blog

High sample rate data acquisition using DAQ and saving data continuously. Also I would like to chunck data into a new file in every 32M

Hi:
I am very new to LabView, so I need some help to come up with an idea that can help me save data continuously in real time. Also I don't want the file to be too big, so I would like to crete a new file in every 32 mega bytes, and clear the previous buffer. Now I have this code can save voltage data to TDMS file, and the sample rate is 2m Hz, so the volume of data increase very fast, and my computer only have 2G ram, so the computer will freeze after 10 seconds I start to collect data. I need some advise from you briliant people.
Thanks very much I really appreciate that.
Solved!
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Attachments:
hispeedisplayandstorage.vi ‏33 KB

I am a huge proponent of the Producer/Consumer architecture. But this is the place I advise against it. The DAQmx Configure Logging does all of it for you!
Note: You will want to use a Chart instead of a graph here.
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Attachments:
hispeedisplayandstorage_BD.png ‏36 KB

MyRIO memory, data transfer and clock rate

Hi
I am trying to do some computations on a previously obtained file sampled at 100Msps using myRIO module. I have some doubts regarding the same. There are mainly two doubts, one regarding data transfer and other regarding clock rate.
1. Currently, I access my file (size 50 MB) from my development computer hard drive in FPGA through DMA FIFO, taking one block consisting of around 5500 points at a time. I have been running the VI in emulation mode for the time being. I was able to transfer through DMA from host, but it is very slow (i can see each point being transferred!!). The timer connected in while loop in FPGA says 2 ticks for each loop, but the data transfer is taking long. There could be two reasons for this, one being that the serial cable used is the problem, the DMA happens fast but the update as seen to the user is slower, the second being that the timer is not recording the time for data trasfer. Which one could be the reason?
If I put the file in the myRIO module, I will have to compile it each and every time, but does it behave the same way as I did before with dev PC(will the DMA transfer be faster)? And here too, do I need to put the file in the USB stick? My MAX says that there is 293 MB of primary disk free space in the module. I am not able to see this space at all. If I put my file in this memory, will the data transfer be faster? That is, can I use any static memory in the board (>50MB) to put my file? or can I use any data transfer method other than FIFO? This forum (http://forums.ni.com/t5/Academic-Hardware-Products-ELVIS/myRIO-Compile-Error/td-p/2709721/highlight/... discusses this issue, but I would like to know the speed of the transfer too.
2. The data in the file is sampled at 100Msps. The filter blocks inside FPGA ask to specify the FPGA clock rate and sampling rate, i created a 200MHz derived clock and mentioned the same, gave sampling rate as 100Msps, but the filter is giving zero results. Do these blocks work with derived clock rates? or is it the property of SCTL alone?
Thanks a lot
Arya

Hi Sam
Thanks for the quick reply. I will keep the terminology in mind. I am trying analyse the data file (each of the 5500 samples corresponds to a single frame of data) by doing some intensive signal processing algorithms on each frame, then average the results and disply it.
I tried putting the file on the RT target, both using a USB stick and using the RT target internal memory. I thought I will write back the delay time for each loop after the transfer has occured completely, to a text tile in the system. I ran the code my making an exe for both the USB stick and RT target internal memory methods; and compiling using the FPGA emulater in the dev PC VI. (A screenshot of the last method is attached, the same is used for both the other methods with minor modifications. )To my surprise, all three of them gave 13 ms as the delay. I certainly expect the transfer from RT internal memory faster than USB and the one from the dev PC to be the slowest. I will work more on the same and try to figure out why this is happening so.
When I transferred the data file (50MB) into the RT flash memory, the MAX shows 50MB decrease in the free physical memory but only 20MB decrease in the primary disk free space. Why is this so? Could you please tell me the differences between them? I did not get any useful online resources when I searched.
Meanwhile, the other doubt still persists, is it possible to run filter blocks with the derived clock rates? Can we specify clock rates like 200MHz and sampling rates like 100Msps in the filter configuration window? I tried, but obtained zero results.
Thanks and regards
Arya
Attachments:
Dev PC VI.PNG ‏33 KB
FPGA VI.PNG ‏16 KB
Delay text file.PNG ‏4 KB

Different Sampling rates for different channels in Analog Input

Hi,
I would like to acquire data at different sampling rates on different channels say ACH 0, ACH 1 and so on. I have a PCI 6052E board and NI DAQ 6.9.2. Also is it possible to simultaneously perform Analog output on two different channels along with the Analog input? What will be the problems/consequences as far as the system resources are concerned. I am a beginner in this area and would greatly appreciate any help/pointers for my queries.
Thanking you in advance
Deepak

Search the eaxamples that ship with LV.
Theer is one called simultaneous input and output or something like that.
It will get you started.
re: multiple scan rates. This is acoomplished by sampling all channels at the highest rate and throw away the expttra samples you do not need.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

PXI-7831R analog input max sampling rate?

I'm using 5 of the analog inputs on the 7831R and seem to only be able to get a max sampling rate of 10K per channel. Looking at the specs it should do at least 10 times this per channel, also the time for the A/D loop is 228 ticks of the 40MHz clock so this would suggest a higher sampling rate than just 10K. I'm missing something here... Any ideas as to what the deal is?
pete

Hi Pete,
You are right in saying that the 7831R boards should acquire data much faster than 10KHz. Infact you can take a look at the actual specs from the data sheet http://sine.ni.com/nips/cds/view/p/lang/en/nid/14757 as well as the product manual. However, I am concerned that you may be measuring the rate of acquisition on the RT VI (or any host vi) you are running as opposed measuring it in the FPGA VI.
Your time critical loop may be running at 228 ticks of the 40 MHz clock but the data is buffered (at that rate) and has to be then transferred to the communication loop which then sends the data to the host vi (which may be your RT vi). Hence, the rate at which host VI receives the data will be much slower than the FPGA VI is acquiring data.
Hope this helps!
Prashanth

MyRIO analog input express Vi (n samples) missing file

Dear Users,
I am trying to read analog data with an express VI in myRIO. This works with Analog input (1 sample), but fails with Analog input (n samples) due a missing file "myRIO v1.1 FPGA Throughput.lvbitx".
I googled it and searched it on ni.com, but nobody seems to have the same isssue (I suppose because of the myRIO is quite new right now)
Thank you!
Solved!
Go to Solution.

I would try doing a repair of your installation. It looks like something didn't get installed properly.
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Sample rate and data recording rate on NI Elvis

I am currently working on a project that requires me to record my data at 1ms intervals or less. Currently the lowest timing interval I can record is at 10ms. If I change my wait timer to anything below 10 the recorded data in excel will skip time. For example instead of it starting at 1 ms and counting 2,3,4,5,6...,etc. It is skipping from 2,5,12,19,....,etc. So my question is if it is a limitation that I have reached on the NI Elvis or if it is possibly a problem with how I've created my LabVIEW code. My program from an operational stand point is working great, but it is my data recording that is causing me to not be able to move to my testing phase. Any help on this matter would be greatly appreciated.
Other information that might be relevant:
Operating System: Windows 7
Processor: Intel(R) Xeon(R) CPU E31245 @ 3.00 GHz
Memory: 12GB
DirectX Version: 11
Attachments:
Count Digital(mod12).vi ‏76 KB

Hi crashdx,
So my immediate thought on this issue is that the code inside your primary while loop might be taking too long to process to achieve such a high sample rate. Especially when making calls into external applications (such as Excel) which can take a large amount of itme.
There is a very useful debugging tool called the Performance and Memory tool. If you aren't familiar with this tool, it will allow you to see how much memory the various chunks of your code are using and, more importantly here, how much time each subVI is taking to execute. Does the code inside your while loop take longer than 1ms to run? If so, then you will definitely see unwanted logging behavior and will need to change your approach. Would it be possible to collect more than a single sample at a time and perform calculations on a large number of samples at once before writing them to Excel in bigger chunks?
I've included a link to the LabVIEW helpful detailing the Profile Performance and Memory tool.
http://zone.ni.com/reference/en-XX/help/371361H-01/lvdialog/profile/
I would first try and figure out how long it's taking your loop code to execute and go from there.
I hope this helps!
Andy C.
Applications Engineer
National Instruments

Adjusting Sampling Rate to write continuous data to excel?

Dear colleagues,
I am reading data from a DAQ from 4 channels and am wanting to write the data continuously to an excel sheet. Problem is, I cannot get the sampling rate and # of samples to appear "constant". instead, labview is only sampling x number of samples in a row and storing those to excel. What I want is this:
Beginning at time t=0, and every 0.2 seconds after that (5 Hz), read the values from all 4 channels and append them to an excel file. What I am using is a 1D to 2D array converter and the Write-to-Spreadsheet function outside my while loop. If I set it to only do 1 sample every 0.2 seconds, then it just stays at t=0, just refreshing the value and thus overwriting my excel data. How can I make it sample continuously from t=0 to t=when STOP button is pressed, and then log all samples into excel? I have attached my sample vi below. Thank you.
Attachments:
working_final.vi ‏547 KB

Hi Mike, Thanks for replying.
The latter of the two methods you mentioned, " you write your values every iteration to the file, therefore you have to place the "Write vi" inside the while loop.", this would be ideal. What sort of conversions need to be done in the while loop before the data is written? In my file, you can see that I am trying to use a converter to go from Dynamic Data to a 1D array. Would this be the appropriate method for doing this? What I am trying to accomplish can't possibly be this complex, I'm sure lots of people require the use of a similar write-to-spreadsheet function.

How to store the sampling rate into the header of the data file?

I want to store the data parameters such as sampling rate to the data file. Now I am using the Write Labview Measurement File VI, the data is saved, but like the sampling rate this kind of parameter is not in the file. How can I store this parameter?

If you want the sampling rate to appear in a different location of the header, then it and it's subVIs can be modified to write anyway you want. Right click on the Express VI and slect Open Front Panel. Then you have a VI that can be modified. If you want to use an unmodified Write LabVIEW Measurement File, you could use that, read the whole file back in with one of the file read functions, insert a string with the sampling rate and then write the whole thing back out again. It might be simpler though, to use Write Characters to File to create your own header and then use Write to Spreadsheet File to write the data. There is also the function Export Waveforms to Spreadsheet File on the Waveform>Waveform File I/O. This uses a slightly different format than a .lvm file. It too can be modified if you don't like the default header.

Record data at one sample rate and calculate velocity

I need to record position data at a sample rate of 10 hz but I would like to calculate velocity every half a second. What is the best way to do this so the velocity display does not jump? I want to capture quick responses but I would also like to calculate the velocity over a longer period of time like 1 minute.

I am trying to calculate vertical speed based on pressure altitude data. I am using serial communication to measure pressure at 10 Hz. I am using Labview 8.2 for all of the calculations and measurements.
I am looking for some way to average the data over some time interval that I have yet to determine. I want to be able to see any major pressure changes whithin about .5 seconds but I also need to see trends over a longer time period say 2 to 10 seconds.
I have thought about using an array and then averaging the array or implimenting a rolling digital filter.

MyRIO aggregate sample rate

Hi Forums,
Quick question, the myRIO AI sample rate is 500kS/s aggregate on the MXP connectors (A and B).
My current thoughts are that connecting to inputs on AI0-AI3 on MXP connector A, would give me 125kS/s per channel, therefore ~ 62.5kHz bandwidth (please correct me if I'm wrong).
What I'm trying to work out, is whether the 500kS/s gets split between the total inputs shared between MXP A & MXP B; or is it 500kS/s aggregate per connector? I.e. If I split my inputs to AI0-AI1 on MXP A; and AI0-AI1 on MXP B, would I be able to increase my sample rate per channel?
Kind thanks,
Tori
Tori
Student
Solved!
Go to Solution.

Hey Tori,
Here is a thread on a similar question: http://forums.ni.com/t5/Academic-Hardware-Products-ELVIS/Question-about-myRio-Hardware-ADC-DAC/td-p/...
Any I think my answer in that thread (copied below) should answer your question:
The best way to think about the myRIO hardware is as if it has two ports the MSP and MXP (don't distinguish between A and B on the MXP connectors).
The MSP AI, MXP AI, and Audio In (ie all the AI) share the same ADC.
The MSP AO and Audio Out each have their own DAC but share an SPI line.
The MXP AO has its own DAC and has its own SPI line
Let us know if you have additional questions!
-Sam K
LabVIEW Hacker
Join / Follow the LabVIEW Hacker Group on google+

Problems with Sampling rate in LabVIEW with 1/4 bridge strain gage

Hello,
I have a question. I have SCXI 1001 and am trying to read strain gages and thermocouples. In the slot 1 I have a 1122/1322 with thermocouples that works great. In slot 2 I have a 1121/1321 that needs help. I cannot figure out how to make a LabVIEW program to read the strain gage.
Is computer hardware a factor? I have a relatively old Dell, 1.7 ghz, 256 MB RAM, and all of my programs bog my machine down. My thermocouple program with 1 functioning channel takes almost 2 minutes to load.
Anyway, I program the DAQ assistant like I think it should be done, but I am having problems with the sampling rate. Everytime I run the program I get an error message saying that it could not get the recommended samples in time. I have had my delay time on my While Loop as low as .25 s and as high as 1.5 s. I have changed my sampling rate from 1 hz to 1000 hz.
I would really appreciate any and all help on this matter. I am still very new to LabVIEW. <I could not contain my excitement when my thermocouple program worked>
Thanks,
CDawgttu

Hi CDawgttu,
I think the best thing that we can do for the moment is to try and see what the maximum rate you can get on the 1121 is, when working on its own.
According to the DataSheet the 1122 is more likely to be what's slowing you down. There could also be some concerns with how the internal jumpers are set on the 1121, so you may want to make sure that the settings there match how you have configured your board in Measurement and Automation Explorer.
-You can set this up by right clicking on the SCXI module and adjusting the Properties. On the Jumpers Tab you should then make sure the values match what you've set internally (SCXI-1121 User Manual - Chapter 2)-
When you use just the 1121, see if that makes a difference in your overall application speed.
Finally, it may be easier to use an example program than the DAQ Assistant since you are using such an old machine. You can find Strain Gauge examples by opening LabVIEW and following this path:
Help > Find Examples > Browse > Hardware Input and Output > DAQmx > Analog Measurements > Strain > Cont Acq Strain Samples.vi
I hope some of these tips get you pointed down the right path.
Regards,
Otis
Training and Certification
Product Support Engineer
National Instruments

Labview myRIO Analog data sampling rate

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