Acquiring and Averaging DAQmx Values

All,
I am aquiring two voltage signals, one from a differential probe and one from a clamp-on current probe.
Two questions:
1. How do I configure my DAQ device, a USB-6212 in this instance, to aquire one signal on AI 0 and the other signal on AI1?
2. Is there an automated way to do the averaging? My For Loop works, but it is not elegant.
As always, any help would be greatly appreciated. Image and LV2009 code attached.
Thanks!
Attachments:
Fluke Voltage and Current.JPG ‏70 KB
Read and Graph Fluke Voltage and Current.vi ‏18 KB

To use a different scale for each, wire one DAQmx Create Channel to the next with the same task - not separately as you have done.

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Bind Variable in SELECT statement and get the value in PL/SQL block

Hi All,
I would like pass bind variable in SELECT statement and get the value of the column in Dynamic SQL
Please seee below
I want to get the below value
Expected result:
select distinct empno ,pr.dept   from emp pr, dept ps where   ps.dept like '%IT' and pr.empno =100
100, HR
select distinct ename ,pr.dept   from emp pr, dept ps where   ps.dept like '%IT' and pr.empno =100
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----- TABLE LIST
CREATE TABLE EMP(
EMPNO NUMBER,
ENAME VARCHAR2(255),
DEPT VARCHAR2(255),
LOC    VARCHAR2(255)
INSERT INTO EMP (EMPNO,ENAME,DEPT,LOC) VALUES (100,'TEST','HR','NYC');
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CREATE TABLE COLUMNAMES(
COLUMNAME VARCHAR2(255)
INSERT INTO COLUMNAMES(COLUMNAME) VALUES ('EMPNO');
INSERT INTO COLUMNAMES(COLUMNAME) VALUES ('ENAME');
INSERT INTO COLUMNAMES(COLUMNAME) VALUES ('DEPT');
INSERT INTO COLUMNAMES(COLUMNAME) VALUES ('LOC');
COMMIT;
CREATE TABLE DEPT(
DEPT VARCHAR2(255),
DNAME VARCHAR2(255)
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PL/SQL BLOCK
DECLARE
TYPE EMPCurTyp IS REF CURSOR;
v_EMP_cursor    EMPCurTyp;
l_col_val           EMP.ENAME%type;
l_ENAME_val       EMP.ENAME%type;
l_col_ddl varchar2(4000);
l_col_name varchar2(60);
l_tab_name varchar2(60);
l_empno number ;
b_l_col_name VARCHAR2(255);
b_l_empno NUMBER;
begin
for rec00 in (
select EMPNO aa from EMP
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for rec in (select COLUMNAME as column_name from columnames
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LOOP
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END;
END LOOP;
END LOOP;
END;

user1758353 wrote:
Thanks Billy, Would you be able to suggest any other faster method to load the data into table. Thanks,
As Mark responded - it all depends on the actual data to load, structure and source/origin. On my busiest database, I am loading on average 30,000 rows every second from data in external files.
However, the data structures are just that - structured. Logical.
Having a data structure with 100's of fields (columns in a SQL table), raise all kinds of questions about how sane that structure is, and what impact it will have on a physical data model implementation.
There is a gross misunderstanding by many when it comes to performance and scalability. The prime factor that determines performance is not how well you code, what tools/language you use, the h/w your c ode runs on, or anything like that. The prime factor that determines perform is the design of the data model - as it determines the complexity/ease to use the data model, and the amount of I/O (the slowest of all db operations) needed to effectively use the data model.

How can I do to acquire and save date in the same time and in the same file when I run continual my VI without interruption.

I've attached a VI that I am using to acquire amplitude from Spectrum analyzerse. I tried to connect amplitude ouput to the VI Write Characters To File.vi and Write to Spreadsheet File.vi. Unfortunately when I run continual this VI without interruption, labview ask me many time to enter a new file name to save a new value.
So, How can I do to aquire and save date in the same time and in the same file when I run continual my VI for example during 10 min.
Thank you in advance.
Regards,
Attachments:
HP8563E_Query_Amplitude.vi ‏37 KB

Hi,
Your VI does work perfectly. Unfortunately this not what I want to do. I've made error in my last comment. I am so sorry for this.
So I explain to you again what I want to do exactly. I want to acquire amplitude along road by my vehicle. I want to use wheel signal coming from vehicle to measure distance along road. Then I acquire 1 amplitude each 60 inches from spectrum analyzer.
I acquire from PC parallel port a coded wheel signal coming from vehicle (each period of the signal corresponds to 12 Inches). Figure attached shows the numeric signal coming from vehicle, and the corresponding values “120” and “88” that I can read from In Port vi.
So I want to acquire 1 time amplitude from spectrum analyser each 5
period of the signal that I am acquiring from parallel port.
So fist I have to find how can I count the number of period from reading the values “120” and “88” that I am acquiring from In Port (I don’t know the way to count a number of period from reading values “120” and “88”).
Here is a new algorithm.
1) i=0 (counter: number of period)
2) I read value from In Port
3) If I acquire a period
i= i+1 (another period)
4) If i is multiple of 5 (If I read 5 period)
acquire 1 time amplitude and write to the same
file this amplitude and the corresponding distance
Distance = 12*i). Remember each period of signal
Corresponds to 12 Inches).i has to take these
values: 5,10,15,20,25,35,40,45,50,55,60............
5) Back to 2 if not stop.
Thank you very much for helping me.
Regards,
Attachments:
Acquire_Amplitude_00.vi ‏59 KB
Figure_Algorithm.doc ‏26 KB

How to use and configure DAQmx software triggering in Labview 7.0

Dear NI support staff,
I want use to software triggers to start and stop acquiring an indefinite amount of analog samples (as opposed to a fixed number of N samples in most of your code examples). I don't know the correct way to configure the DAQmx property nodes and the DAQmx send software trigger VIs. In the property node VI it doesn't seem to have an entry for software trigger. So I think I am not on the right track. Would you please help me out? It would be great if you can show me an example. Thanks a lot!
Regards,
Bennett

Hello Bennett,
The example below demonstrates how to perform an analog software triggered acquisition in NI-DAQmx. The example allows the user to specify the triggering condition and the number of pre-trigger samples to acquire.
Example Code - Triggering
Let me know if you have further questions.
Good luck and have a great day!
Regards,
Koninika
Applications Engineer
National Instruments

Finding and averaging multiple rows

Hello,
I am having a little problem and was wondering if anyone had any ideas on how to best solve it.
Here is the problem:
- I have a large file 6000 rows by 2500 columns.
- First I sort the file by columns 1 and 2
- then I find that various rows in these two columns (1 and 2) have duplicate values, sometimes only twice, but sometimes three or four, or five or up to 9 times.
- this duplication occurs in only the first two columns, but we don't know in which rows and we don't know how much duplication there is. The remaining columns, i.e. column 3 to column 2500, for the corresponding rows contain data.
- Programatically, I would like to find the duplicated rows by searching columns 1 and 2 and when I find them, average the respective data for these rows in columns 3 to 2500.
- So, once this is done I want to save the averaged data to file. In each row this file should have the name of colunm 1 and 2 and the averaged row values for columns 3 to 2500. So the file will have n rows by 2500 columns, where n will depend on how many duplicated rows there are in the original file.
I hope that this makes sense. I have outlined the problem in a simple example below:
In the example below we have two duplicates in rows 1 and 2 and four duplicates in rows 5 to 8.
Example input file:
Col1 Col2 Col3 ... Col2500
3 4 0.2 ... 0.5
3 4 0.4 ... 0.8
8 5 0.1 ... 0.4
7 9 0.7 ... 0.9
2 8 0.1 ... 0.5
2 8 0.5 ... 0.8
2 8 0.3 ... 0.2
2 8 0.6 ... 0.7
6 9 0.9 ... 0.1
So, based on the above example, the first two rows need averaging (two duplicates) as do rows 5 to 8 (four duplicates). The output file should look like this:
Col1 Col2 Col3 ... Col2500
3 4 0.3 ... 0.65
8 5 0.1 ... 0.4
7 9 0.7 ... 0.9
2 8 0.375 ... 0.55
6 9 0.9 ... 0.1
Solved!
Go to Solution.

Well, here's an initial crack at it. The premise behind this
solution is to not even bother with the sorting. Also, trying to read
the whole file at once just leads to memory problems. The approach
taken is to read the file in chunks (as lines) and then for each line
create a lookup key to see if that particular line has the same first
and second columns as one that we've previously encountered. A shift
register is used to keep track of the unique "keys".
This
is only an initial attempt and has known issues. Since a Build Array is
used to create the resulting output array the loop will slow down over
time, though it may slow down, speed up, and slow down as LabVIEW
performs internal memory management to allocate more memory for the
resultant array. On the large 6000 x 2500 array it took several minutes on my computer. I did this on LabVIEW 8.2, and I know that LabVIEW 8.6
has better memory management, so the performance will likely be
different.
Attachments:
Averaging rows.vi ‏30 KB

Overall Average and Average of part of data-set displayed simultaneously

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Hi James,
It looks to me like your code is not giving you the results you desire because of an assignment syntax error. You want to add all the Upr_Values together and then divide by the Upr_Count to get the overall average for the upper lobe. Your code, though, just overwrites the previous Upr_Value with the current one and assigns the value +1 to Upr_Count each time:
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Upr_Count = Upr_Count + 1
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[email protected]

Calculate total and average for same key figure

Hi Experts,
I have a requirement where I need to calculate total and average for same key figure no of employees.
eg:
If I enter 03,2009 as Input the reuslt should give from financiual year starting to current month.
     11.2008      12.2008     1.2009     2.2009     3.2009        average
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total         21         20       23       22        20          21.2
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Waiting for your Inputs.
Regards
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no it will work for u
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lets say that variable is zcalmonth
it is based on 0calmonth for e.g.
now u restrict keyfigure with this variable zcalmonth with time char. = 0CALMONTH
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now set offset for variable in variable selection screen dialog box = -1
repeat this until u want
make this variable mandatory
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now there can be maximum 12 months in a year, so u end up creating only 12 restricted keyfigures.
use YEAR in restricted keyfigure too, and restrict it with YEAR VARIABLE processing by CUSTOMER EXIT = CURRENT YEAR
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for e.e.g
YEAR = 2008 only
User entered 6/2008
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4/08
5/08
6/08
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Where to put data processing routine when acquiring data using DAQmx

I have a program that is aquiring data using the DAQmx Acquire N Samples mechanism with automatic reset and a data handler callback routine. DAQmx acquires N samples (usually 1024) from the board, calls the handler to do something with it, and then resets to get the next batch of data. The program acquires a number of lines of data, say 512 lines of N points each, with one callback call per line. Triggering is done by a hardware trigger at the start of each line of data. So far so good.
The issue is that the time that it can spend in the callback is limited, or else the callback is not finished when the next batch of data is ready to be transferd from the DAQmx buffers and processed. There is a substantial amount of analysis to be done after the entire frame has been acquired, and it ends up taking far longer than the time between lines; so where to put the processing? The data acquisition is started from a control callback callback that exits back to the idle loop after it starts the data acquisition process, so there is no code waiting to execute, to return to, when the data acquisition is finished.
I could try to put the data analysis routine into an idle-time routine and trigger it with a semaphore, or I could put it into a timer control callback with, say, a 10 millisecond repetition rate and poll a flag, setting the flag when all of the data has been acquired. Any suggestions would be appreciated.

I would recommend using Thread Safe Queues. Your acquisition callback can place items in the TSQ and then you can process the data in a separate thread. TSQs are nice because they allow you to install a callback function to run for certain events. Most importantly, you can install a callback for the Items in Queue or Queue Size Changed event which will run the callback if a certain number of items are in the queue. This lets you take advantage of multithreading in a simple and safe way using a standard Producer/Consumer architecture. However, you may still run into problems with this architecture if your acquisition thread is running much faster than the consumer thread. You could eventually overflow the queue. In that case, your only options are to either get a faster system, slow down the acquisition or do the data handling post process.
National Instruments
Product Support Engineer

Acquiring signal using DAQmx 6221

I'm new to using DAQ. I need some pointers on how to go about the following
issue. I want to acquire a sine wave through DAQmx (PCI 6221). I need to
acquire the signal at a particular rate and store it as a binary and ASCII
file. Also I want to know how to output a signal through DAQmx. Could you
please give some pointers and example VIs if any?
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Go to Help>Find Examples. Then expand Hardware Input and Output>DAQmx. Also look at Getting Started With DAQmx.

How can I acquire and record pre trigger samples

Hi I would like to acquire and record pre trigger samples. I have used many different methods including:
http://digital.ni.com/public.nsf/allkb/9DE9E3E4DAD9EE93862579C60018B6EA
the problem is I would like to acquire pre trigger samples before start trigger not reference trigger. I think reference trigger is used for stop triggering not start triggering. Could you please help me on this
Thanks?

Hi tintin_99,
I hope you are well and thank you for posting your issues to the forum.
I wanted to ask you some further information in regards to your application:
- What version of LabVIEW do you have?
- What operating system (OS) are you running on your PC/laptop?
- Which application programming interface (API) are you using? NI-DAQmx, NI-Scope?
When you mention you want to acquire the pre-trigger samples before the start trigger and not the reference trigger, how are you currently doing this? Would you be able to post up your code so that everyone can have a look at it?
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- Continous Analog Input Acquisition with Pre-trigger Scans using 2 E-series Boards
- How Can I Acquire Pretrigger Samples with NI-SCOPE?
- Software Analog Trigger with Pre-Trigger Samples
- Synchronized Analog Input/Ouput with an Analog Trigger and Pre-Triggered Samples
I hope this is alright for now.
Kind Regards,
Dom C

Dithering And Averaging With The 6025e Board

Hi Guys,
I'm trying to acquire a video analog signal, using the 6025e board. I've read that this board is able to dither and/or average the data stream in order to improve the signal and lower the noise.
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Hi AnalogKid2DigitalMan, thank you very much for your reply.
First, can you please explain why I can reliably sample only 100KHz signals maximum ?
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B. Does dithering/averaging lower the effective sample rate of the board ?
Your help is kindly appreciated.

64 channel 1450 Hz data logging with PCI-6033E card, on-line averaging and viewing the raw and averaged signal in CWGraphs.

I'm acquiring 64 channels at sampling rate of about 1450kHz continuously and showing the data second by second in a CWGraph. Now, I would like to add an on-line averaging for all of those 64 channels and show it in another CWGraph. The averaging should occur with respect of external trigger and the sample should consist of about 100ms prestimulus and 500ms poststimulus period. Has anybody been handling this sort of things? How it's solved with ComponentWorks and Visual Basic?
I'm using double Pentium 700MHz processors and NI-DAQ PCI-6033E card.

1. To get started with external triggering check out the examples in the Triggering folder that install with CW under MeasurementStudio\VB\Samples\DAQ\Triggering.
2. Create a prestimulus buffer that always contains the latest 100 ms of data. Just modify the CWAI1_AcquiredData event to transfer ScaledData (the data acquired) to your prestimulus buffer. See how there will always be a prestimulus buffer of data regardless of trigger state?
3. On the trigger, you can use the same CWAI1_AcquiredData event to route the data into poststimulus buffer and average the 2.
I see something like this:
if no trigger
100 ms of data to prestimulus buffer
if trigger
500 ms of data to poststimulus buffer
averaging and display function
reset trigger and buffers
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ben schulte
application engineer
national instruments
www.ni.com/ask

Send analog trigger every time data is acquired and saved

I am currently writing a program that acquires and calibrates data from 32 channels of force plates. Once the data is acquired and calibrated it is saved to a file. I need to send a pulse to another computer running labview once every time data is acquired and saved. I have written several versions of this code that send a continuous pulse train while data is being saved. I need to modify the code so that it does not send a continuous pulse, but an individual pulse that is a set frequency every time I acquire data. I believe that I need to use a software trigger to control the pulse, but I can't seem to find a way to have the hardware send a pulse only when I want it to.
The program uses a boolean as a start trigger for the acquisition process. In this manner when the data begins saving(i.e. the boolean is switched) it would send one analog pulse per iteration of the save loop. Unfortunantly I only seem to be able to either send a continuous pulse that I start before the acquisition begins or am not able send any pulse. During the time this pulse is being sent I am also constantly acquiring data from the card. I was wondering if there is any way that I can have the pulse start and initialize before the loop begins and then have it send one analog pulse of a set frequency every time the loop is iterated. I have tried both DAQmx and DAQ traditional solutions but have had no success.
Hardware: PCI-6071-E and BNC-2110 boxes, so I have a large selection of ports and my card seems to be compatible with all the latest software capabilities.
Thanks so much for any help!
~Matt

Actually after tinkering with it for several hours I managed to figure out a way to solve my problem. I'll explain it in case anyone else has a problem.
What the software does: The software is an acquisition loop that outputs a square wave pulse of finite frequency to another acquisition system at the beginning of each acquisition iteration while data is being saved. This is so that the data from the two systems can be synchronized later.
The program flow is this Send Single Synchronization Pulse-> Acquire Data->Calibrate Data->Save Data to file->Repeat
The pulse is triggered once data begins saving, but the device begins acquiring data on execution of the software.
To do this I set up the DAQmx Channl configuration to CO Pulse frequency. I then set the timing up to be finite iterations and the number of iterations to 1. Inside the acquisition loop I enclosed the whole acquisition process in a flat sequence. In the first sequence, if the program is saving data it turns the pulse on, if not saving the task passes through. The acquisition occurs in the middle sequence and in the final sequence if saving the task is turned off. If not saving the task passes through. This allowed me to send one pulse of a finite frequency every time the loop is run.
Thank you very much for your response though. If anyone else runs into a problem like this I can post a screenshot for future reference when I get a chance. Thanks again.

Acquiring and Averaging DAQmx Values

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