How to acquire 1 data point per trigger ?

Dear all, anyone can help me in acquiring 1 data point per trigger? just as a Sample/hold circuit?
I changed the example from Labview "Acquire 1 point digital trig", however, it doesn't work, it says data acquiring is inconsistent with buffer. The program is attached.
and I try to use "AI Sample channels.vi", but there is not trigger input and sampling rate input.
Thank you very much for your help.
Attachments:
Acquire1PointTrig.vi ‏81 KB

There is a good example that can do almost exactly what you want to do. It is called Acq&Graph Voltage - Int Clk - HW Trig Restarts.vi. There are only three things you need to change. Change the triggering VI to trigger off of a digital signal, then change the read VI to read a single channel and single sample and finally, change the Samples per Channel to 2. I have included screenshots of the VI.
The VI works by setting up a digital start trigger that is retriggerable, so that you can have this trigger start the acquisition over and over. Once the trigger happens, a sample is acquired, read, and then the hardware waits for another trigger.
Have a great day,
Brian
Message Edited by Brian C on 03-28-2007 01:48 PM
Brian Coalson
Software Engineer
National Instruments
Attachments:
block diagram.Jpg ‏54 KB
front panel.Jpg ‏58 KB

Similar Messages

How can I find an example about acquiring waveform data by software trigger using PXI 4070 DMM?

Anybody could proivde an example or simliar about acquiring waveform data by software trigger using PXI 4070 DMM?
Thanks!

hi there
from the NI main page go to the developer zone http://www.ni.com/devzone/dev_exchange/ex_search.htm. select "LabVIEW" and "Digital Multimeter (DMM)" and search for "4070". then you'll find some examples.
Best regards
chris
CL(A)Dly bending G-Force with LabVIEW
famous last words: "oh my god, it is full of stars!"

How to remove noisy data points read from a text file

Reading data measurements taken in from a txt file. How do I get rid of noise aside from going into the text file and deciding point by point what to delete.

Well going in point by point and deleting is certainly one way of going about it. Of course that would defeat the entire purpose of having this great programming enviroment that is capable of doing that kind of thing for us.
Is your text file small enough to upload? Obviously you know what the criteria are for judging whether or not a data point is acceptable so it should be simple enough to program. Give us a bit more information and I can assure you there will be a race between LabVIEW experts to see who can post the cleanest, simplest, and fastest piece of code that will do what you need. My wager is on altenbach, but there are a few others here that are almost as impressive.

How to delete the Data Points label with a crosstab layout

Hi, just a question.
I created a report which uses a crosstab layout; so...I have the Company Name on the left, Status Code above and the Count(tickets) as Data Points.
As soon as I put the Count(tickets) inside the report, the label "Data Points: Incident Id Count appears above just at the bottom of the Status Code
Is there a way to avoid this tedious label ?
As workaround, I changed the Data Points' format heading (text and background) in such a way to see only a Grey space...but this is not so useful (from the customer side...)
I also looked for inside the crosstab layout properties...but I didn't found nothing.....
Any help will be appreciate
Alex

Well, I think you are out of luck. You are basically saying you want to control when you have a column heading and when you don't want to have a column heading. Most of us users do want column headings in our reports. In fact I have a hard time trying to figure out why you don't want a column heading. How are the report users going to know what the numbers in the column mean if you don't have a heading on the column? Maybe the initial users of the report know, but what happens when they leave and someone else takes over their duties? I would suggest putting in an enhancement request for Discoverer to give you the option to not display a column heading, if you really want something like this. This needs to be at the workbook level, I am thinking.
John Dickey

How to add more data point in Pie chart

The default data point for Pie chart is 5, how could I add more data point, I notice that I can do assign the cell to the value under data in General tab property of chart pie, but, in the sample drill down, there is no value for that value, and it still has 6 data point.

Hi DFW
The sample file has got the spreadsheet range missing thats all. Just add the range you need to your pie chart.
Regards
Charles

How can I label data points in a scatter chart with text strings?

Post Author: Bill B
CA Forum: Charts and Graphs
I need to create a Scatter Chart, with a text label for each data point instead of the xy coordinates. A legend will no longer be necessary.Also, I want to draw "cross-hair" lines on both the x and y axes centered on one particular data point.Any ideas?

Post Author: ebobo
CA Forum: Charts and Graphs
Hi
I have the same problem here, did you find any solutions.
Here we are ok if the dimension is displayed in the scatter instead of the measurements but the only options i founds was "Show data" and that option displays the values of the xy.
pls let me know if anybody found any solution for this problem

How to remove values data points from Apex3 Flash Chart

Hi
I am using a Apex 3.2 and I have to put Flash Charts in my application. But since the charts have are smaller in size, I do not want to have the data points coming up in the chart. I have planned to show them using hints. But unfortunately, I am not able to hide the Data Points. Can you please help. Thanks Sahcin. Here is my custom XML.
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<root>
     <type>
          <chart type="Stacked Horizontal 2DColumn">
               <animation enabled="no"/>
               <hints enabled='yes' auto_size='no' width='200' height='20' horizontal_position='left' vertical_position='top'>
                    <text><![CDATA[{NAME}, {VALUE}]]></text>
                    <font type="Verdana" size="10" color="black"/>
                    <background color="0xF4F4F4"/>
               </hints>
               <arguments show="no"/>
               <names show='yes' position='top'/>
               <values show="no" prefix="$" postfix="" decimal_separator="." thousand_separator=',' decimal_places="2"/>
               <column_chart column_space='20' block_space='20' left_space='0' right_space='0' up_space='0' down_space='0' round_radius='0'>
                    <border enabled="no"/>
                    <block_names enabled="yes" placement="chart" rotation="45" x_offset="0" position="left">
                         <font type="verdana_embed_tf" size="8" color="0x000000"/>
                    </block_names>
                    <background type="gradient" gradient_type="linear">
                         <alphas>
                              <alpha>100</alpha>
                              <alpha>100</alpha>
                              <alpha>100</alpha>
                         </alphas>
                         <ratios>
                              <ratio>0</ratio>
                              <ratio>120</ratio>
                              <ratio>0xFF</ratio>
                         </ratios>
                    </background>
               </column_chart>
          </chart>
          <workspace>
               <background enabled="yes" type="solid" color="0xF4F4F4" alpha="0"/>
               <base_area enabled="no"/>
               <chart_area enabled="yes" x="100" y="50" width="600" height="300" deep="0">
                    <background enabled="yes" type="solid" color="0xCCFF99"/>
                    <border enabled="yes" size="1"/>
               </chart_area>
               <x_axis name="Region" smart="yes" position="left_center">
                    <font type="Verdana" size="10" color="0x000000" bold="no" align="center"/>
               </x_axis>
               <y_axis name="Booking Amount (kUSD)" smart="yes" position="center_bottom">
                    <font type="Verdana" size="10" color="0x000000" bold="no" align="center"/>
               </y_axis>
               <grid>
                    <values>
                         <lines size='1' color='0x15771A' alpha='100'/>
                    </values>
               </grid>
          </workspace>
          <legend enabled="yes" x="0" y="0" rows="2" rows_auto_count="no">
               <names width='80' enabled='yes'/>
          </legend>
     </type>
     #DATA#
</root>Edited by: user779712 on Nov 3, 2009 4:45 PM
Edited by: user779712 on Nov 3, 2009 4:46 PM

Well going in point by point and deleting is certainly one way of going about it. Of course that would defeat the entire purpose of having this great programming enviroment that is capable of doing that kind of thing for us.
Is your text file small enough to upload? Obviously you know what the criteria are for judging whether or not a data point is acceptable so it should be simple enough to program. Give us a bit more information and I can assure you there will be a race between LabVIEW experts to see who can post the cleanest, simplest, and fastest piece of code that will do what you need. My wager is on altenbach, but there are a few others here that are almost as impressive.

How to save one data point at every 10th cycle?

Hello,
I am using LabVIEW 5.1 and PCI-6023E. In my application, I need to detect peak values from a load cell and save the one data point that detected at every 10th cycle. Do you know any ideal way to do this? Mine always save data values the whole time that the condition is true which is about 26 values; not one value as I want. Any help would be greatly appriciated.
Hao

Hello Justin,
Thank you very much for helping me out. I did not state my question clearer last time. Actually, the cycle here is the number of life cycle of a valve that being tested; therefore, the iterator i can be any number when the valve's life cycle reaches its 1st, 11th, 21st....cycles. Do you know any other way to do this?
Thank you in advance
Hao

How to insert the data even the trigger returned null

Hi Gurus,
I have a question regarding on how to insert the record even the condition being used by a "before insert trigger" returned null.
The scenario is:
2 tables have the same structure:
Table A (Name varchar2 (100), No Number)
Table B (Name_1 varchar2 (100), No Number)
A script is using to load the data into table A daily, and a “before insert trigger” is being used to get the value for A.Name = B.Name whenever the condition A.No equals to B.No.
If the B.No exists, then the trigger work fine, otherwise the records will be rejected, this is not the way we wanted, so I just wonder, is there any way to load all the data to the other fields but still using this trigger ?
Thanks,
Tran

Either amend the select in the trigger that gets the name value to not raise a NO_DATA_FOUND exception (e.g. change "select name..." to "select min(name)..." ) or handle the NO_DATA_FOUND exception in an exception handler.
e.g.
EXCEPTION
WHEN no_data_found THEN
:new.name = 'where the streets have no name';

How to acquire serial data on a digital input line with good performance?

Hello,
we have a performance problem with our realtime controller. Our objective is, to read a 24-bit long digital waveform from a digital input line. To do this, we supply a clock signal (236 KHz) to the PFI1 Line of our DAQ Board. On each rising edge of the clock, a new bit is set on the digital input DI0.
Our hardware which transmits the data, is triggered through a digital output from our realtime controller. On each edge on this output, the hardware starts a serial transmission of 24-Bits.
Everything works fine except the bad performance of our realtime controller. We want to acquire the 24-Bits in a 1ms timed loop. To measure performance we wrote a test program. In that, we only triggered the hardware and transfered the data to the realtime controller. The task which is doing this job, has a approx. CPU-Load of 30%, which is, in my humble opinion, very high. The task is not waiting for data or anything else! We have earlier implemented a control which is also using a 1ms timed loop. This control is sampling 2 analog input signals, 2 counters. Futhermore it's sending telegrams with CAN and doing many calculations. The strange thing is, this much huger program has a CPU-Load of 25%. Does anybody know where the problem is?
For the better understandig I attached our test-program to this text.
We're using:
PXI-8175 realtime controler
PXI-6221 Multifunction DAQ
Thanks!
Regards,
Crest!
Attachments:
dig_test.zip ‏51 KB

Hello,
First of all 30% CPU-Load is normal because the DAQmx-driver needs a lot of resources.
In your programm you should place a wait (for example with 1ms) into the while-loop which causes
lower CPU-Load.
If this is not enough you should build your vi like in the following example.
Regards,
Christian
Attachments:
Read Dig Port.vi ‏51 KB

How to quickly select data point symbol?

hi, take line chart for example. sometimes there are a lot of series data in one chart and it often happens that one series partly covers another. In such case it is not easy to click the symbol which I want to modify color.
Is there any keyboard shortcut to achieve this or does anyone know any tips?
thank you.

Setting the Numbers View zoom to 400% can help to separate the lines and points. Beware that at that high zoom level, it may still take some patience to select the correct series, but it's easier than if they are all on top of one another. Another way is to temporarily modify one of the datapoints in the series you wish to select so that it stands away from the rest. After you have made the change, you can restore the correct data.
Jerry

How to calculate the data as per accounting year

I want to dispaly the result for the accounting year from April to March for any accounting year (Accounting year is from April to March).
I have a table INVOICE.
CREATE TABLE INVOICE
IN_NO       NUMBER,
IN_DT       DATE,
IN_DETAILS VARCHAR2(20 BYTE)
I want to calculate display the result for accounting year from April 2010 to March 2011, and from April 2011 to MArch 2012.
What statement should i use to filter the data as above ?
Sanjay

user12957777 wrote:
I want to dispaly the result for the accounting year from April to March for any accounting year (Accounting year is from April to March).
I have a table INVOICE.
CREATE TABLE INVOICE
IN_NO       NUMBER,
IN_DT       DATE,
IN_DETAILS VARCHAR2(20 BYTE)
I want to calculate display the result for accounting year from April 2010 to March 2011, and from April 2011 to MArch 2012.
What statement should i use to filter the data as above ?
Sanjay
You should learn now to use correct tags
select to_char(add_months(in_dt,-3),'YYYY') FISCAL_YEAR FROM INVOICE;

Reducing Number of Data Points Acquired?

I am interested in knowing how to reduce the number of data points written to a file that was acquired at 5 Hz. I have tried to lower the sampling frequency below 5 Hz on a Compaq Daq, but I get an error saying that is an incorrect value. So, if I can't sample below 5 Hz, how do I acquire fewer data points, or how do I reduce the number of data points written to the file? I have tried Sample Compression which just ignores data points. So, an acquired value is written multiple times at the same rate as having no compression at all. I calculated the sampling frequency from the data file witha compression ratio of 20, 30, and 40 to still be at 5 Hz.

If you want to "compress" your data then you should perhaps try the "Decimate (single shot) VI " Owning Palette: Signal Operation VIs. With this VI you can average down an array. If you have an array sampled with 5Hz and you set the decimating factor to 5, and average=true. Then the output will be an an array downsampled to 1 Hz, with each value equal to the average value of 5 samples in the input array. The decimate function is quite new. It came in Labview 8.2
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

How to writing the data into the file at the same frequency of data acquisition using myRIO

Hi everyone,
I have a question regarding data acquisition fequency and data recording frequency of myRIO. Hope you guys can help me out.
Basically, I want to acquire voltage input at analog input 0 at the frequency of 1kHz and then write the data into a file (tdms format).
However, I always found there were only 55 or 56 data points recorded every second in the data file (see the excel sheet).
To confirm my data acquisition was performed at the correct frequency, I added a small function in the main loop to indicate the time spent between two acquisition events.
To my surprise, the period of data acquistion is correct (1ms or 1kHz) but there are only 55 or 56 data point per second recorded in the data file.
How can I record every data point acquired by the analog input?
Thank you!
P.S. I am very new to myRIO. How can I manually set the system time for myRIO? The default time of my myRIO is wrong.
Best,
Tengyang
Attachments:
test result.xlsx ‏16 KB
Main with timed loop.vi ‏122 KB
test result.xlsx ‏16 KB

Have a look at the Jakarta POI project, they have a Java API for creating Word documents.
http://jakarta.apache.org/poi/hwpf/index.html

Data points

I'm having a bit of an issue. I have a cycle counter that counts the TTL of a function generator and I'm collecting 100 data points per "cycle" My cycle count is being saved to the data file in the first column, along with 4 analog channels. My issue is: My cycle count isn't always exactly 100 per cycle in the data file. It's close but not exact. Is this a timing issue or something in my code?
Attachments:
CSS Complete - Final29.vi ‏435 KB

Hi glskinner,
It sounds like it is probably just slight inaccuracies in the clock on you device. What device are you using? How far off is the count? If we look through the specifications sheet of the device we should be able to determine if the discrepancies you are seeing are within spec.
Best Regards,
Thomas B.
National Instruments
Applications Engineer

How to acquire 1 data point per trigger ?

Similar Messages

Maybe you are looking for