Samples to Read y Rate

Buenas tardes, estoy trabajando con la daq ni6009, la utilizo para medir las rpm de un motor de inducción, a través de un swicth óptico. Con un samples to read de 10k y un rate de 20k la lectura de la velocidad me sale aceptable, el problema es que me salen solo dos o tres datos por segundo y yo necesito 20 datos/ segundo (en un archivo). Al cambiar el simple to read y el rate toma mas datos (hasta 10/seg) pero el valor de la medición es erróneo y tiene muchos saltos.
Ah los datos de la medición los guardo en un archivo de Excel, y al guardarlos aquí es que lo hace 2 datos/segundo; ya que la tarjeta si esta adquiriendo bien los datos con el simple to read(10k) y el rate(20k)
Que podría hacer para tener una buena medición y más datos por segundo?
Gracias

Buen día.
Le adjunto mi Vi, y unas imágenes en el cual le explico cual es el problema.
De antemano Muy agradecido por quien pueda ayudarme.
Attachments:
Pregunta.docx ‏139 KB
Tesina2.vi ‏483 KB

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Samples to Read and Rate (Hz)

In the DAQ Assisant window, there are two options for reading samples:
1. 'Samples to Read'
2. 'Rate (Hz)'
Could someone please define the meaning of these? the context help did not clearify the meaning of these for me.
Examples would help also:
for example right now I have the settings at:
Samples to Read: 1
Rate (Hz): 200
what does this mean in terms of samples read per second?
Am i recording data at 200 Hz?
Any help would be greatly appreciated.
Cheers,
Oliver
Solved!
Go to Solution.

What is your sample type (Continuous, Finite Samples, Single Sample)?
If you are using Continuous, then the sample rate is how often a sample is taken. Not sure in the DAQ Assistant, but with the DAQmx Timing VI, the number of samples sets the buffer size.
If you are using Finite Samples, then the sample rate is the same as the Continuous, but the number of samples is how many samples you want in a single acquisition. The DAQ card will not continue to gather samples between reads. It only gathers the defined number of samples with each read.
If you are using Single Sample, then neither of those settings are useful. The card will just take a single sample and be done.
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DAQ Assistant: Clock Settings (Samples To Read, Rate) can affect signal readings?

Dear all,
I'm totally new to Labview, and recently I get confused with the equipment I'm dealing with.
Technical details:
The Labview version is 7.1; computer operate system is Windows XP;
The equipment has a NI PCI-6220 and a 68 Pin Connector Block to read signals from the equipment;
There are 4 channels in DAQ Assistant (2 pressure reading, 2 temperature reading);
For the first pressure reading, Signal Input Range from 4m to 20m Amps;
Clock Settings are Samples To Read = 5, Rate (Hz) = 20.
Description of the problem:
I use Labvew to monitor and record pressure readings and temperature readings. The Labview configuration was set up by my advisor several years ago. Recently, I found the pressure reading vibrated a lot; for example, 5.01 to 5.05 bar within a second. In order to get a stable pressure reading, my advisor suggested me to change "Clock Settings" in DAQ Assistant from Samples To Read = 5, Rate (Hz) = 20, to Samples To Read = 250, Rate (Hz) = 1000. In this case, she believed that since we increase sample numbers and sampling rate, we could have more data, and thus have stable pressure readings.
At first I could have very stable pressure reading. The last digit (0.01) did not change within 20 seconds. However, somehow after a day the pressure reading became unstable and even worse than previous. (pressure reading vibrates from 5.01 to 5.30 within a second)
This is not the worst case. We found that when we set Clock Settings: Samples To Read = 5, Rate (Hz) = 20, the pressure reading is about 8 bar. However, when we set Clock Settings: Samples To Read = 250, Rate (Hz) = 1000, the pressure reading is about 5 bar. In this case, we even don't know which pressure reading is correct.
Labview records current, and transforms it into pressure reading. Thus my advisor tried to monitor the current reading by Labview, and she found the current reading changed when she changed the Clock Settings. (0.004 Amps (5 bar) when Samples To Read = 5, Rate (Hz) = 20; 0.005 Amps (8 bar) when Samples To Read = 250, Rate (Hz) = 1000)
Since we only change the sample numbers and sampling rate, the average readings should still be similar. However, the reading are not similar. That is what confuses me.
My questions are, if Clock Settings in DAQ Assistant could affect signal readings? If so, how it could affect the signal readings? What is the effect of "Samples To Read" and "Rate (Hz)"? How to determine these parameters to get the true pressure readings?
Thank you very much for your help. Hope to have some feedbacks from you.
Best regards,
Cheng-Yu
Energy and Mineral Engineering
the Pennsylvania State University

A 6220 cannot read a current, it can only read a Voltage, so you'll probably have some (or should have) a resistor accros the voltage input. (normally 50 Ohm for a 0-20 mA signal).
My first step would be to measure this voltage with a multi-meter so you know what the actual voltage should be.
Then I would read that same voltage with MAX (measurement and automation explorer) to make sure you have the right value
Now about the changing of the voltage/current/pressure, how have you terminated the other signals? Have you provided a good earthing?
If you sample with a high frequency (1 kHz), perform an FFT on the acquired data, I can imagine a dominant 50 or 60 Hz (depends on where you live) in the signal that might cause your problem.
Ton
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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,
Alaeddin

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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Problème NI usb 6211, sample rate et sample to read

Bonjour,
je viens vers vous car je souhaite faire une acquisition continu d'un signal d'une entrée analogique. Sur cette entrée analogique est branchée un accéléromètre et un transducteur qui me renvoie donc une tension (120Mv/g) . J'ai donc réalisé à l'aide d'un exemple labview un programe. Cependant, celui-ci est très très long .. Lorsque je varie la tension d'entrée, cela prend plusieurs secondes avant d'afficher la valeur exact. Une erreur 200279 s'affiche lrosque les paramètres de sample read et sample rate ne correspondent pas... j'ai été voir sur le net sur ce lien :
http://digital.ni.com/public.nsf/allkb/AB7D4CA85967804586257380006F0E62
Mais rien n'y change. je vous laisse mon Vi en pièce jointe... cordialement
Attachments:
Test 1.vi ‏28 KB

Bonjour Geoff54,
Tu es sur le forum international donc si tu veux que quelqu'un te reponde tu devrais poser ta question en anglais.
Sinon il éxiste un forum francophone : French Forums
L'erreur que tu rencontres vient du fait que le buffer du PC se remplit avec les données que tu acquiers mais tu ne le vide pas assez vite et lorsque le buffer est complet il te renvoie l'erreur -200279.
Pour solutionner celà, il faut que tu viennes vider le buffer plus rapidement.
Tu peux faire celà en augmentant le "sample to read" à plus que 1000 ou bien en laissant la valeur par défaut qui est -1.
Bonne journée,
Valentin
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What are supported sampling frequency and digitization rates for Zen Micropho

Some MP3's are playing back slowly. It is inconsistent, though, since files with the same digitization rate and sampling frequency will behave differently - some right speed, some slow.
The bulletin board says:
"My tracks don't play at the correct speed e.g. they play too slowly, why?
Chances are they are encoded in an unsupported sampling frequency..."
How do I find out what the supported sampling fequencies and digitization rates are?

Thanks for the info. I guess I was looking for something more specific - the exact bitrates and sample rates that Creative claims to support. Would you know where official and comprehensi've data can be had? There must be a tech spec somewhere.
It is common these days in business to see a recording of, say, a conference call or seminar presentation at 32k bitrate/025Hz, or even 24k bitrate/8000Hz, posted to a company's website for download by those who could not be there, and MP3 players are increasingly used for their replay. Companies use low digitization rates because there is no need for hifi and the files are much smaller: less storage, faster download.
I'd be surprized to think that Creative don't have compatibility with the standard range of rates offered by ubiquitous programs like Audacity and dBpower, the latter being one they themselves recommend!

Samples to read option in DAQ

Hello,
          I am new to signal processing and confused about the DAQ Assistance option "samples to read".
What I understand is about
Sampling rate indicates the samples read per second, I run my vi for a second and I got 10K samples when my sampling rate is 10k. Frequency resolution is also depend on this sampling rate and Samples to read.
My settings in DAQ Assistance are
continuous acquisition, Samples to read--1K, sampling rate--10K and I run my Vi for exactly one second and I got 10K samples but I am confused about "Samples to read". What it is exactly?
Thank you.

You can't write "nothing" in that box. The value must be 1 or greater.
It is a bit confusing, because in Continuous Mode, it really isn't Samples to Read, it is a range of buffer sizes - which was described in the previous reply.
Check out the HELP >>> Buffer Size
How Is Buffer Size Determined?
Input Tasks
If your acquisition is finite (sample mode on the Timing function/VI set to Finite Samples), NI-DAQmx allocates a buffer equal in size to the value of the samples per channel attribute/property. For example, if you specify samples per channel of 1,000 samples and your application uses two channels, the buffer size would be 2,000 samples. Thus, the buffer is exactly big enough to hold all the samples you want to acquire.
If the acquisition is continuous (sample mode on the Timing function/VI set to Continuous Samples), NI-DAQmx allocates a buffer equal in size to the value of the samples per channel attribute/property, unless that value is less than the value listed in the following table. If the value of the samples per channel attribute/property is less than the value in the table, NI-DAQmx uses the value in the table.
Sample Rate
Buffer Size
No rate specified
10 kS
0–100 S/s
1 kS
100–10,000 S/s
10 kS
10,000–1,000,000 S/s
100 kS
>1,000,000 S/s
1 MS
Note  For performance reasons, the default buffer size for continuous acquisitions differs slightly when logging is enabled.
You can override the default buffer size by calling the Input Buffer Config function/VI.
NI-DAQmx does not create a buffer when the sample mode on the Timing function/VI is set to hardware-timed single point.
Note  Using very large buffers may result in diminished system performance due to excessive reading and writing between memory and the hard disk. Reducing the size of the buffer or adding more memory to the system can reduce the severity of these problems.
Richard

PLEASE can a AE from NI take a look at my problem. Sound input read behave in strange manner then the buffer size is larger than 2X number of samples to read.

On my computer I have discovered some strange behavior then reading data from the sound card. Then the buffer size is 2x samples to read everything is as expected. But since I read the sound card 10 times pr second I feel a .2 second buffer is to small. I am using XP, and XP is not a RTOS so with a buffer set to 0.2 seconds I may lose data. Therefore I set the buffer size (number samples/ch on Sound Input Configure.vi) to be in range of 2 seconds. The result then is that then reading from Sound input.vi, a reading often take more than 0.1 second. On my computer it is often 500mSec. Then the next 5 read follows with almost zero interval. I do not loose data. But on my front panel the graphs looks like an very early silent movie. This error was introduced in Labview 8.x. To be honest I think the labview 7.x sound system was much better in many ways.
But before I point any finger NI. Other people has to verify the behavior I experience. I have made an example showing this error. It is a modified version of the "Continuous Sound Input.vi" example. Then the "buffer in seconds" control is set to 0.2 every thing works OK. Changer this to a larger number will produce the mentioned above hiccup. The larger number in this control the larger hiccup. Is it any way to fix this? My solution up to now has to use a free 3. part software(http://www.zeitnitz.de/Christian/index.php?sel=waveio) But I guess it soon will be outdated. It may not work with newer windows versions.
Any help at all will be appreciated
And yes I have the most updated version fo DirectX. Also I se this in Labview 2009 which I have trail version of. The VI I have made is in 8.6
Message Edited by Coq Rouge on 09-07-2009 10:54 AM
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)
Attachments:
Continuous Sound Input with timing.vi ‏23 KB

macaba wrote:
If you take a moving average of the 0.2s buffer vs. 3s buffer at an update rate of 10, then they are the same (just under 100ms), so the average refresh rate is the same. I agree that is odd behaviour that the time between sound reads go to zero quite a lot then take a long time once in a while (presumably to fill the buffer
I guess it goes to zero because it is reading data from the buffer it do not has to wait for data from the sound card. The mysterious thing is the periodic delay. You are also correct then saying that average timing is correct. And in my application I have no data loss.
If you search for sound in this forum you will find out that many people has reported trouble with the sound system.
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

Sample per channel and sample to read

Hello everybody
I am new in LABVIEW and I have some difficulties with something.
I don t know exactly what is the difference between the sample per channel et the sample to read. I believe knowing that the sample per channel is the size of the buffer which is more big than the sample rate but I don t know what is the sample to read.
I ve tested with different sample per channel and sample to read. Sometimes I have an error and sometimes know and I would like to know why. If you have any example for I understand better, it will be great.
I really need to understand this part for my project
Thank for your help
Romaric GIBERT
Solved!
Go to Solution.

Hi Roro,
As you mentioned, when acquiring continuous samples you can specify the sample buffer size by placing a value at the input "samples per channel" on the timing vi. The "number of samples per channel" input on the read vi which automatically names a control/constant with "samples to read" specifies the number of samples you wish to pull out of the buffer in one go when reading multiple (N) samples. This link may provide a bit more clarification. I have also attached a good example from the NI example finder which you may find useful to explore. I'm assuming you are using the DAQmx driver set so please let me know if this is not the case, but the same principles should apply either way.
This therefore means when sampling at a given rate, you need to ensure you are pulling data out in big enough 'chunks' to prevent the buffer from overflowing (which may well be causing the error you are seeing). Conversely if your sampling rate is slow and your read vi is having to wait for the number of samples to read you specified to be available, it may throw a timeout error. You can avoid this by either increasing your sampling rate, reducing your samples to read or increasing the timeout specified at the read vi input (-1 means it will wait indefinitely).
Let me know if this helps and how you get on.
All the best.
Paul
http://www.paulharris.engineering
Attachments:
Cont Acq&Graph Voltage-Int Clk.vi ‏27 KB

Raw Read Error Rate, Errors occurred while reading raw data from a disk

hi
when I turn my pavilion dv6 2170ee computer on screen shows below error.
system diognostics (F2) does not any work
and when my windows7 comming up this error was shown.
I install Hard Disk Sentinel software and this program shows below:
Failure Predicted - Attribute: 1 Raw Read Error Rate, Errors occurred while reading raw data from a disk. Indicate problem with the disk surface or the read/write heads.
There are 28 weak sectors found on the disk surface. They may be remapped any time in the later use of the disk.
26848 errors occured during data transfer. This may indicate problem of the device or with data/power cables. It is recommended to examine and replace the cables if possible.
Replace hard disk immediately.
how can I fix it?
may drive format (Fdisk) and renewing windows can fix it?
tanx and regards
Mohammad

Hello mohkhosh,
I see that you're getting an error indicating possible hard driver failure, that you have this message from 3 different sources. I will try to help you with this.
After reviewing everything you're looking at needing to replace the hard drive. I would suggest contacting support to see what they can do for you.
HP Technical Support, North America 1-800-474-6836. For all other regions click here.
Thank you for posting on the HP Forums.
I worked on behalf of HP.

Raw read error rate warning,what should I do?

Hi,I have an HP Pavilion DV6 3103sl,
,it comes with a 320 gb seagate hdd(ST9320423AS),
the raw read error rate is below the average limit,
the hard disk is new, less than one year of life without a heavy use,it never overheated
here' s the test
http://i1142.photobucket.com/albums/n607/goldberg14/Rawreaderrorrate.jpg
should I have this replaced?
obviously the lap is still under warranty

I would say it is just beginning to fail. Call HP and see if they will replace it based on that test, which is not technically a failure but a "watch".

Why can I only write the samples to read during continuous acquisition?

I am acquiring analog voltage signals and attemting to write to a text file when condition is true, thus there is continuous acquisition. However, the written files only contain 100 samples (the size of my buffer).. I need my files to read samples until the while loop is stopped. How can I go abotu doing this?
Thanks,
TFlax
Solved!
Go to Solution.

I have been able to make this work, but it only writes the buffer size. I am new to labview and programming in general and I have tried to make a producer and consumer design however I dont seem to understand the concept properly and fail to run my program properly... So here's my code before any attempt to producer/consumer design which only writes 100 samples to file. Advice on how to modify it to producer/consumer because Im not even sure where to start.
Thanks,
Tflax
Attachments:
Test_Signals_Dec17.vi ‏745 KB

Sampling Inspection at variable rate during Receiving process

Hello,
We would like to perform sampling inspection during receipt process, actually we perform sampling for couple of supplier, the QA procedure is to inspect 10% of the total qty( we don't have lot/serial control set for items), if any failure then need to increase sampling rate to another by 10%.
As I understand Quality module in 11.5.10 allows for sampling at receiving process. But I am not sure, does it allow for above requirement to perform at different sampling rate based on failure.
Looking forward for your expert comments.
Thanks,

In quality module, you can setup rules that can alter the sampling rate. It is called skip lot inspections.
e.g. you can say that
* inspect 1 in every 5 shipments.
* But if any shipment is found bad, inspect 3 in every 5 shipments.
* Once 10 consecutive inspections are successful, then revert back to 1 in every 5 shipments.
Keep in mind the functionality works on number of receipts - not quantity in each receipt.
First you have to enable your org for skip lot inspections
Then you define a skip lot process code. This is where you define your logic/rules.
Then setup your sampling collections plan.
Hope this answers your question
Sandeep Gandhi
Omkar Technologies Inc.
Independent Techno-functional Consultant

Custom samples for read aloud books

I have uploaded a fixed layout read-aloud book and it needed a custom sample before it could go into the IBookstore. Imade one and reuploaded but now it says I still need a sample for the origina l as well as the preview. What am I doing wrong? In the asset guide it says something about type="preview" I assume that means that I have to insert something in the metadata of the preview to say it is a preview Is this right? If so can anybody tell me exatly what I need to insert.
Thanks in Advance
Bagsybaker

You're not doing anything wrong. I used iTunesProducer and got the same message. So I called the people at iTunesConnect and tech told me it says that but it showed on his end. A week later my Children's ebook was in the iBookstore along with my sample being available.

About FM 'READ EXCHANGE RATE'

Hi,
The FM 'READ_EXCHANGE_RATE' documentation says that the exchange rate valid on a date is read from table TCURR according to the currency key and the exchange rate type.
But I find that for some situations, the picked up
Exchange rate is not found in table TCURR.
In debugging I see that it reads from internal table BUFFER and not by making a SELECT query from TCURR.
Only when records are not in BUFFER it makes a SELECT query to TCURR.
My requirement is to find latest Exchange rate b/w two currencies. So I pass the current date as the Currency translation date.
Even if the value for the current date is not available in TCURR, it should pick up the latest one.
So when the FM READ_EXCHANGE_RATE is run, sometimes the BUFFER table is filled up with records having
values for the current date and these records are not found in TCURR table.
As these exchange rates sometimes are not found in TCURR for the Currency keys / Ex. rate type, can anybody please explain me the purpose of the BUFFER table and where from the Exchange rate is picked up.
Regards,
Midhun.

For the first time Buffer doesn't have any data...After selecting the data from data base the buffer will be filled up....!!! Then if you are in the same session and try to use the FM once again the value gets picked up from BUFFER internal table which is ok......
As and when you come out from the transaction/session...The Buffer will be refreshed....since it's an internal table...
Thanks
Suresh

Samples to Read y Rate

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