Hardware digital trigger to start stop continuous analog acquisition

Hi I have seen the following example to use digital trigger to start and stop for finite number of samples. The example names is (DigitalStartandStopTrigger.vi)
in this example Reference Digital edge is used to stop acquisition but if I change to continuous then Reference Digital edge stops and show an errir. Could you please let me know how can I use hardware digital trigger to start stop continuous analog acquisition. An example would be really great
many thanks

HI tintin_99,
The way that example works (by modifying the read position of the buffer) essentially performs the same operation that the continuous samples mode does. That is to say, it is already a continuous acquisition.
The article below explains this in more detail, and the reasoning behind specifying buffer size manually and other tricks used. You may have already visited it in order to get the example VI, in which case it may be worth another read over.
http://digital.ni.com/public.nsf/allkb/BA775B0E445BFA79482571FE0032CCEB
Kind Regards,

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Digital trigger to start other device

Hello can anyone help me create Vi to generate digital trigger to start another device. I have agilent u2531A measure card and LabView 2010, and want to generate digital trigger to start generate signal on Rigol 4000 generator.

Ok, here is a possible solution to your problem. But I am not sure it will work properly so please give me some feedback. Also, as you will see, I set a sine wave as a defaut output signal from Rigol DG4000.
To have the functions I used for your devices, you have to install the appropriate drivers: LabVIEW>Help> Find Instruments Drivers then select the manufacturer and select the driver from the list.
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AgilentTrigger_RigolGen.vi ‏31 KB

Reusing digital trigger on PCI-6733

I am working with a PCI-6733 analog output card. I would like to use the digital trigger to start a waveform, then use it to start another waveform without stopping the first (then start a third while the first two are running, and so on). I don't need to reroute the trigger signal - all the pulses can (but don�t have to) come through the same PFI terminal.
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Hello Matt,
I believe you can do it only if you use different PFI lines to trigger your waveforms. You won't be able to do it with one digital trigger, that's why you were getting those errors.
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How to use digital trigger with analog I/O

How do I program analog input and/or analog output to start on a digital trigger (PFI pin) on PCI-4451/4551.
I have tried out various configuration and succeeded in starting analog input, simultanuous input and output triggered by the the anlaog input signal. I have also succeded i triggering 4551 from the dedicated EXTTRIG pin.
The problem is to trigger on a selectable PFI pin. I find the help for "AI Trigger Config" and "AO Trigger and Gat Config" misleading - some unsupported features seem to work while selecting PFI pin as source make the PC restart immediately.
I have not been able to find any LabVIEW example that shows how to use PFI pin as trigger input.
Using LabVIEW 7.1, NI-DAQ 7.3 on Windows 2000.
Kind regards / Med venlig hilsen
Torben

Hello
The PCI-4451 does not have any PFI lines. If you look at the user manual in the link beneath you will be able to confirm this by looking at the connector signal discriptions. The same is valid for the PCI-4451
http://digital.ni.com/manuals.nsf/websearch/6A32358C53BB15F086256660007392DC?OpenDocument&node=132090_US
The two ways of triggering that you have succeded are the analog triggering and digital triggering that you can peform with the PCI-4451.
Regards
Mohadjer

Why does Start Digital Edge in Start Trigger.vi do a kind of timeout?

Hi I am doing a manual trigger on my hardwareboard by inserting a 5 volt source into the selected triggerchannel a couple of seconds after I push the start button.
The generation never starts. But if I put the trigger signalchannel equal to the external sampling clock the appended vi work.
Example I use PFI7 as trigger source which is also the source of the sampling clock.
Could somebody explain?
Kindest regards,
Lasse
Solved!
Go to Solution.
Attachments:
Cont Gen Voltage Wfm-Ext Clk-Dig StartA.vi ‏36 KB

One cannot just insert a wire with a 5 V potential to PFI6 for instance if PFI6 is used as a trigger for "Start Digital Edge" daqmx -vi. The pin is floating and just inserting 5V does not guarantee a low to high edge.
If I use a potentiometer to pull the channel low first, and then increse the voltage, the trigging happens.

Determine when Counter Pulse Generation has been digitally triggered to start

A counter task has been configured for continuous pulse generation with a digital edge start. How in LabVIEW can I determine when an external digital trigger has been received and the counter started ? It seems that a timed loop with DAQmx Create Timing Source wired to its source could be made to work but I cannot figure out how or the most appropriate instance to use. I would simply stop the timed loop once the counter start had been detected.
Steve

Querying the output state and looking for a change would probably work for many typical square-like pulsetrains. If you have an extreme duty cycle like 1% or something though, your queries are likely to keep finding the counter in the same output state long after pulses have started.
Some other ideas of a similar nature may work better, though I'm not near a LV machine to test them. I can vouch for idea #1 from past usage though.
1. Query the counter's 'count' property and look for a change. You're pretty unlikely to query the same count value several times in a row during pulse generation.
2. You could try querying the DAQmx property for "TotalSamplesGenerated" and look for a non-zero value. I'm not sure if this gets updated for counter outputs though.
3. Counters also have a property called "TC reached?" where TC means terminal count. When you query and get a True, It automatically resets itself back to False until reaching TC again. Again, while I know this works for counter input tasks, I'm not sure if it gets updated for counter outputs.
-Kevin P.

Digital Trigger Vs Software Trigger.

I'm running an MCC USB-FS1608 DAQ to measure multiple analog voltage channels. I also have a digital in TTL coming from an MTS 407 frequency controller. Inside my VI, I read a rising TTL signal from the MTS, send a signal to switch on the digital out, then I start my data acquisition. At 1 Hz, would it be better to control my digital out, (which sends a run command to the MTS which then actuates a hydraulic piston) with a hardware trigger?
Solved!
Go to Solution.

Hardware communication in the sense that you are referring to is not necessarily universal. Especially when utilizing third party hardware/drivers. If the drivers they have created are built on top of NI-DAQmx then you could possibly use our functions to do this. To do the functionality you are wanting you would need to:
-Configure Digital Output task with the channel you want to output on
-Configure Digital Start Trigger giving it the channel you want to read from (TRIG_IN). For some hardware, they might allow rising edge triggers as well as falling edge triggers which would then be some property you would have to set.
-Configure write task to output a digital high or 1 on your digital output channel
-Start task
-Loop until finished
-Clear task
This is about as general and universal as it gets but the actual implementation of each step might be different based on the driver. Physically, the only changes you would have to make are wiring your digital start trigger into the TRIG_IN input instead of into one of the digital input lines.
Ian M.
National Instruments

Digital trigger mac OSX

Hi everybody
I am running a machine mac OSX snow leopard with Labview 2011. The acquisition card is a PCIe-6259 with a connection box SCB-68. I would like to perform the acquisition of an analog signal according to a digital trigger (PFI0 or PFI1). I have created this simple VI that unfortunately does not work on my machine. The VI exits immeditely without doing anything and I do not have even an error. If I switch to analog trigger it works nicely but it is slower than I need. If I run the same VI on a windows machine it works fine. What am I doing wrong?
Thank you very much for all the tips
antonio
Attachments:
Trigger_acquisition_test2.vi ‏23 KB

I do not have any hardware so I cannot test. Try putting an error indicator (or probe) on the error wire coming from the Start Trigger VI to be sure that you are not getting an error. I keep automatic error handling turned off, so I am not sure, but I think that wiring the error out terminals changes the way it works. Put an error indicator at the end of the chain also.
Lynn

Generate counter output based on a digital trigger

I am trying to output a train of pulse based on a digital trigger (GO bit). When the GO bit goes high, I want to output a pulse train after an initial delay (ie: 2 seconds). When the GO bit goes low, I want to stop this pulse train. When the GO bit goes high again, I want to start the same pulse train with the same initial delay.
The output pulse train has 2 frequencies so I am using 2 counters that generate the same pulse but one of them is delayed by a certain amount. Then I combine the output from both counters into one output using simple BNC T connector. Since I am using 2 counters (max # of counters available to me), I can't create a finite pulse train.
If I use a pause trigger, the only problem is that the second time the GO bit goes high, the initial delay is not used (each channel or counter has a different delay).
So far the only way I can think of is by software timing the counter (by counting the time since the task has started) and stopping the task once certain amount of time has passed. Then I wait for a second trigger which should start the pulse train again with the initial delay.
Is there a better way to do this?

One more thing:
Is there any way to use a digital trigger that is based on two different digital signals ANDed together? I basically want to output the pulses when 2 digital inputs are binary 1 at the same time.

Which is the best structure for start/stop data logging?

Hi everybody,
hope I can explain my problem good enough that anyone can help me:
I have a VI which continuely shows on a graph the voltage of a Analog Input of a DAQ device. Now I want to allow the user to start/stop with a click on a button data logging. Means that a second loop writes to a selected path every ms the data to a spreadsheet file.
At the moment my VI works like this:
You run the VI and Labview asks you one time for the file path, then you can start and stop the data logging. But you can do it only one time. If you want to log a certain time later another file, you have to close and open the whole VI again which is not very professional...
My target is:
It is onlyl necessary to start the VI one time. Then you can select a new file path, log data, select another file path, logging data again....and so on...
Which programm structure is necessary, can anyone help me as a labview beginner with that issue? I attached the VI if someone just wants to edit that...
Thank you for your help!! Markus
Attachments:
Logging voltage.vi ‏93 KB
screenshot.JPG ‏98 KB

@NaruF1 and GerdW
you are right, there is a mistake, both loop rates should be the same (10 ms) :-)
@NaruF1
yes you understood correctly that the file dialog should appear every time the user wants to start writing a new log-file. The voltage we measure is a analog signal, so there will be several interesting periods we want to save for a later analysis in Excel.
To your 2nd point: if it works with a array it will be fine. But it must be possible to log data for lets say 5 minutes, so the array won´t be too large? (5 min @ 10 ms loop rate will be 30000 rows..
attached is the VI, saved as LV2009..
Thanx a lot!
@GerdW
..you ask why I didn´t create a structure like you recommended with notifiers or queues? The simple answer would be that I am not familiar with all this.. just began to write my first Labview programm. I will have al look to the LV help with all that stuff... Thank you a lot
Attachments:
Logging voltage.vi ‏80 KB

Digital triggering for analog acquisition on PCI-6024

I would like to initiate an analog input scan when a digital line goes low using a PCI-6024 board. I connected the digital line to TRIG, and the analog line to AIN0. I tried using "Acquire N - Multi-Digital Trig.vi"...it almost works. It acquires a scan, but it may (randomly) start at either the rising or falling edge of the trigger, regardless of the rising/falling trigger edge setting. How do I get it to only acquire data on a falling edge?

Dear Dave -- If you set up your task using MAX, you can specify whether you need to start acquiring at the rising or the falling edge. Using this task in your experiment should effectively take care of the issue.
You can do the same from LabVIEW as well using the DAQmx Trigger VI and set the acquisition to begin at the rising or falling edge as you may choose it to be.
HOpe this helps = VNIU

Triggered and continuous analog input togeather?

Hi,
I have a program set up based off a shipped LV example involving digital triggering of the analog inputs. It looks at a pulse and reads in ten points from the rising edge continuously. It appears that we are missing some pulse triggers and only reading in 126 triggers/sec instead of 128. We double checked the pulse and the frequency is correct (128Hz) so it seems as if the LV program is missing some of the pulses. Therefore, I want to use another analog input channel on the same 6062E daq card to continuously read in the waveform and see which pulses are being skipped. Is this possible?

Lisa,
I don't believe the E-series architecture will allow triggered and continuous analog input operations to occur in parallel. It is possible to set up different gains/input ranges but I'm 95% sure that the functionality that you are after isn't there.
If you are looking to keep track of the number of pulse seen by your application you could consider the use of a counter to count the number of rising edges seen by the NI 6062E - basically daisy chain the pulse train to the trigger input and the GP_CTR Source pin of the counter you wish to use. There are a number of examples around that should help with this. Running the counter and analog input operations in parallel shouldn't be a big problem - it might be that you would want to set up a buffered event co
unt operation for the counter as this will allow you to track and monitor every single trigger event seen by the counter while your analog input operations continue in parallel.
The other aspect to consider is benchmarking your application with the Profiler. If the problem is that you consistently only see 126 triggers/second, perhaps your acquisition loop is not running fast enough to cope with the data. This can be especially true if any data processing or file storage is taking place inside the acquisition loop. The Profiler will allow you spot bottlenecks and get a better understanding as to the performance of your application.
I appreciate this is perhaps not a direct answer but hope that it gives some ideas as to how to track down the cause of the problems you are experiencing.
Jeremy

Digital trigger source

Hi,
Basic question I'm sure, but have not found an answer despite much searching.
I am developing an application that reads loadcell data(Analog input data) when a photocell is triggered(Digital input), using Labview 8.2 and cDaq 9172 with the Ni 9421 digital card in slot 4
Can I use a start Trigger that will activate the analog input data when the collection when an input signal is high?
I'm finding that the Trigger source does not list my DI card, why?

Hey Tui,
Thanks for contacting National Instruments support. I am curious what AI module you are using. I do see that you are using the 9421, and I assume you are using the 9237 for load cells. Based on that you should be able to use Measurement and Automation Explorer (MAX) to verify that connections are correct and test your triggering. Once you have that verified you can then use the task you created to auto-generate LabVIEW code to get started with. This should allow to start from a working example and then make changes until things break.
To create the task in MAX, right click on Data Neighborhood and select Create New... Then setup a NI-DAQmx task and In the setup on the DAQmx task in MAX you can select the triggering tab to specify the trigger from module 5 and then run the task to see if it works.
There is a video to do all this online in our DevZone that you can view that will help through these steps.
Regards,
Kenn North
Senior Product Manager - Search, Product Data
http://ni.com/search

Multi-buffered acquisition with digital trigger

I have a PCI-MIO-16E1 and I need to do three channel (250KHz/channel - ~400 scans/trigger) multi-buffered acquisition with digital trigger (trigger => 30 Hz).
I could not find any example of multi-buffered acquisition. Could anybody help me?

Hello,
I assume that you are refering to a retriggering setup where each time you recieve a trigger you take 400 samples on each channel at a rate of 250kHz per channel (total scan rate = 3CH * 250kHz = 750kHz).
In order to keep the system hardware timed you can use the two counters on the board to produce a retriggerable pulse train that will act as your scan clock. For example each time the counter recieves a trigger it will output a clock signal of 750kHZ with 400 or so pulses in order to take ~400 scans/trigger.
This clock signal can then act as the scan clock for your 3 channel analog input operation.
Now we have to figure out how to set up the retriggerable pulse train from the counters and have the analog input use the counter output as a sca
n clock.
Good thing there is an example that is already written
http://zone.ni.com/devzone/explprog.nsf/6c163603265406328625682a006ed37d/aab61e455564a04d862568930018e725?OpenDocument.
Good Luck.

Hardware digital trigger to start stop continuous analog acquisition

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