Trigger&Gate VI (Signal Manipulation Library)

I have noticed that, if input signal amplitude is less than 0.4 V pk-pk, my VI doesn't work. Is it my fault, or is it a real limit in Trigger&ate VI? How can I solve it? (Data I have to acquire are usually lower that 0.1V)
Same question, in Italian:
Noto che, se l'ampiezza del segnale di ingresso è inferiore a 0.4 V picco-picco, il mio VI non funziona. E' un errore nel mio VI, oppure è un limite reale in Trigger&Gate VI? Come posso risolvere il problema? (I dati che devoo acquisire sono di solito inferiori a 0.1 V)
Attachments:
Acquisizione.vi ‏267 KB

Hi Marc1uk.
Rather than using Express VIs for your coding, have you considered looking at other VIs available for signal analysis.
There is a VI designed specifically for calculating Cycle RMS called "Cycle Average and RMS.vi" which you can find by right-clicking on your block diagram and using the search from the functions palette. This VI can be used for periodic signals, although I appreciate your concerns that by changing the duty cycle of your PWM signal it may not fulfil your requirements.
To overcome your triggering issue, one of the simplest ways may be to change the parameters for your stop trigger. If you set this to the falling edge of the signal and something like 0.2 then hopefully the triggering will be stopped just before the next trigger gets started.
Unfortunately you're always likely to see some phase delay occurred through software filtering in any language. How much phase delay are you experiencing? One option that may reduce this slightly is to change your Filter Express VI to a lower level "Butterworth Filter.vi" which you can find through the Functions >> Signal Processing >> Filters, palette. For this, you can create constants to configure the VI to the same properties as your express VI i.e. a constant of "3" into the Order input, a constant of "Lowpass" into the Filter Type input and the output of the x*5 expression into the Low Cutoff F input.
Hope this information helps you further on your way! If you have any questions don't hesitate to ask.
Kind regards,
Tori
Tori
Student

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Logic Pro and a guitar to trigger gates?

I am looking for a way to use my guitar signal to trigger two tracks separately in Logic Pro. I want to use a gate or something so when I hit a note on the guitar the drum track will sound and stay sounding for the remainder of the song, while the guitar track will go in and out with the guitar signal so if I stop playing the guitar audio track will silence. How would I set up my gates to do this?
^maybe this will help clarify
both tracks are playing at the same time Drums and Guitar but and I want to trigger both at the same time, I just want the drum gate to open and stay open so the audio file sounds while the guitar gate goes along with the guitar signal (so if I quit strumming the guitar audio track quits sounding but the drums are still audible)
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When an open accelerometer channel reaches certain level (say 4 mV) I need a trigger to start data acquisiton, saving the previous 1.5 seconds of data across all eight channels and then stop recording and store the data six seconds after the trigger was started.
Can DASYLab do this?
Your help's appreciated,
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The trigger modules are all control modules; they all output a TTL type signal, 0 or 5, that can be used by other modules.
In this case, the simple trigger configuration should look like this.
A/D ----------- Trigger ---------------- X Relay ---------------- Write Module
\---------------------------------0
The trigger controls the open and close of the Relay, which release the Analog data that you branched to the second input of the Relay.
--cj
- cj
Measurement Computing (MCC) has free technical support. Visit www.mccdaq.com and click on the "Support" tab for all support options, including DASYLab.

Can't trigger off of signal

I'm using the latest Signal Express with an NI-9233 and an ICP force sensor. When I set up my hardware to measure the first channel, it reads it just fine, but when I try to set up the trigger, the option to use the signal as a trigger is greyed out. The only options available are NONE and SOFTWARE.
Is there something else I need to do so I can trigger off of my input signal?
Thanks.

Hello Jeff,
To add to Christophe’s comments, it is also possible to perform hardware triggering on your 9233. This can be done if you have a cDAQ-9172 NI CompactDAQ Chassis and another cDAQ module that uses the type of triggering you would like to use. An example of such a module would be an NI-9205. With this module installed, you can trigger off of an analog input or a digital input. This trigger event can then be shared over the cDAQ chassis backplane.
For analog input triggering, it is necessary to have an analog input channel from the NI-9205 as the first channel in the scanned channels list in SignalExpress. An analog input trigger channel can then be specified as the channel from the NI-9205. Please see the following screenshot.
After the 9205 is installed in any slot in the cDAQ-9172, you can use the PFI0 line from this module as a digital trigger for your analog input task. Please see the following screenshot.
Message Edited by BrowningG on 11-30-2007 04:48 PM
Regards,
Browning G
FlexRIO R&D
Attachments:
AnalogTriggering.JPG ‏23 KB
DigitalTriggering.JPG ‏20 KB

Trigger an Analog Signals Acquired Continuously

Sto acquisendo un segnale periodico tramite una DAQmx e devo triggerrare questo segnale.
Il mio problema sta nel fatto che devo poter impostare da front panel 3 parametri:
1 livello del trigger
2 isteresi
3 hold off

La scheda in questione non dispone di circuiteria per hardware analog trigger. Sostanzialmente questo significa che non e' possibile far partire l'acquisizione in seguito all'evento hardware scatenato dal superamento di soglia di uno dei canali analogici.
L'unica cosa che puo' pensare di implementare e' un conditional retrieval software. in altre parole, bisogna programmare l'applicazione per far partire una acquisizione bufferizzata continua in background e monitorare in parallelo il buffer di dati acquisiti per verificare quando si verifica la condizione di soglia desiderata con relativo ciclo di isteresi e decidere quindi di prendere i dati successivi e farne log a video o su file.
Questo Esempio puo' essere usato come punto di partenza per sviluppare il codice. E' necessario sostituire il clock esterno che questo esempio usa con il clock interno della scheda (Timing configuration) e quindi implementare il codice per gestire isteresi e holdoff.
Saluti
AlessioD
NI

How to reset collector (Signal Manipulation Express VIs)

Good day,
I have a subvi that use "collector" function to get data from a DAQ card. Everything works fine except that when I called the subvi from mainvi (the start button), the data in "collector" will keep on accumulate and will never start from the beginning. Could someone please tell me how to "reset" the collector on every call made to the subvi?
I have attached the two VI here as reference.
Best Regards,
Liew
Attachments:
mainvi.vi ‏38 KB
subvi.vi ‏833 KB

The Collector Express VI has a "Reset" input. Wire a True to that input and the data in the collector will reset on every iteration of the loop. If you need it to only reset at certain times, then add some logic to your loop that can accomplish the reset when you need it.
Good luck,
-D
Darren Nattinger, CLA
LabVIEW Artisan and Nugget Penman

How to extract the signal out from the waveform by my designated power level?

Dear all,
How can I extract the signal from the waveform accroding to the power level? I read the Trigger&Gate.vi, but this vi extract signal according to the duration time. I want to extract signal according to power level.
As shown in the following figures, the signal I want to process is between 130000 to 140000, if I zoom in, I can see the the useful signal is between 135400 to 138200. The question is how to extract the signal in the zone?
I tried the sub_NoiseEst_And_Chop_Shell.vi in the Packet_based_link example too, but this subvi seemed to be a little slow. Can anybody give me better advice? Thanks in advance!
Solved!
Go to Solution.

I was working on something similar but haven't had time to fully develop it.
My idea was to use an envelope detector (low pass filter) and then use an energy detection VI on the envelope.
Here's where I left off
Anthony F.
Product Marketing Engineer
National Instruments
Attachments:
test.vi ‏331 KB

DAQ Card is inducing noise on an external clock signal resulting in false triggering

I am using an optical encoder as an external clock source for analog measurements with a PCI 6036 card. The optical encoder signal is "filtered" using a Schmitt Trigger circuit and proper shielding practices are used on the encoder cable. I am using a recent version of Labview.
When the TTL square wave signal from the encoder is viewed on an oscilliscope (without the DAQ attached) it is a picture perfect square wave, nothing that would cause any problems.
When I then connect the encoder output to my PFI line (with or without the oscilliscope) I get false triggering due to intermittent (seemingly random...) high frequency noise "blips". Out of 360 expected samples, I will typically get between 2 and 6 "bonus" samples... When captured on a scope, the noise looks like a decaying sine wave and lasts for only a few us. the peak magnitude is tyically around 2 V or so as shown on the scope, which is apparently just enough to make my card grab a sample.
Since the noise is only present when the encoder signal is attached to the DAQ, it seems that the DAQ is somehow inducing noise into the signal.
I have been fighting this problem for a while now and tried the following:
1) I first tried the raw encoder signal, but then added the Schmitt trigger, increased the signal strength of the encoder lines by adding resistors to ground, double checked my shielding, etc...
2) I verified that my ground potential between my card and my conditioning circuit were not causing problems. The conditioning circuit and encoder is now powered of the card itself, which should resolve any possible problem with grounds.
3) Cursed at various inanimate objects (made me feel better but didn't help the situation)
4) Checked if I could set a minimum pulse width required to trigger off of an exernal scan clock (I can't with my hardware.)
5) Swapped my card with a card of a different type (problem is still there)
If anybody out there has some recomendations, I am open to anything.

Hello OSU_Mech_Eng,
I'm not quite sure how the DAQ card could be inducing glitches into
your digital signal. Digital signals from mechanical devices like
quadrature encoders can often be glitchy or bouncy, but your schmitt
trigger should act as a debouncing filter to clean up that digital
signal. It sounds like you have thoroughly troubleshooted this
problem, and I would recommend moving on and trying to use a counter on
your DAQ board to generate the digital signal, rathar than using the
raw signal from your encoder/schmitt trigger.
You were correct when you stated that the best way to do this is by
configuring your counter to perform retriggerable pulse
generation. You can use the signal of from your encoder to gate
the internal clock on your DAQ card, creating a clean digital
signal. By setting the minimum pulse width of the signal, you
will be able to ignore the small glitches in your signal. Here is
a link to some Knowledgebases describing how to do this:
How Do I Remove Glitches or Add a Debounce Filter to My Digital Signal?
How Do I Define the Parameters for Pulse Generation in NI-DAQmx?
For further reference, on all of NI's new M-Series DAQ cards (PCI
625x), the PFI circuitry contains built in debouncing filters to
protect against small glitches in digital signals. If you have an
M-Series card lying around, it might be helpful to give that a try.
I hope this helps,
Travis Gorkin
Applications Engineering
National Instruments
www.ni.com/support

Pulse width modulated signals

Is it possible to generate a fixed frequency with variable duty cycle signals using counter/timer channels of my DAQ 700?
If yes, is there any example I could download?
If no, I am looking for a DAQ card that can handle
the job, I'd appreciate any recommendation.
Another part of my project is to read in a analog signal while generating this pulse width modulated
signal. So far I am not very lucky with one DAQ,
I am thinking of getting two. Does it sound overkill?
Please help.
Thanks

Could you provide a timing diagram for your digital signal?
I am a firm believer that a digital output device such as an NI timer can create any signal, given the proper software or hardware. I once did a high speed, gated, triggered data acquisition with only a single NI timer chip on the AT MIO 16E-1. It required about 75 feet of BNC cable, more PFI wires than you can imagine, four external logic devices (AND and OR, NAND and NOR boxes) all interconnected and basically tangled. I don't think I could repeat that setup without my documentation, but the point is, it worked.
The most important thing from that example is that I used a timing diagram. These are so vital in digital IO and timer applications that its not funny.
If you can't determine ho
w to do what you need from a timing diagram, just send me a copy, let me know what the basic specs are of the DAQ 700 (how many counters, interconnect capabilities, etc) and I can try to help.
Good luck.
As far as reading the analog signal at the same time...well, look at my example. I generated the trigger/gate signal with the card, and then read in the analog data (on several channels simultaneously.)

My HAMAMATSU C4742-95-12-NRB camera is not working in EMD E (External Edge Trigger)

Hello!
I am trying to control the HAMAMATSU C4742-95-12NRB camera externally through an external trigger pulse.
There are two modes in the exposure setting command:
EMD E - External Edge
EMD L - External Level
The camera is working fine in the External Level mode (EMD L). I send an external pulse (through ARDUINO) and, after changing the pulse from low to high, the camera starts the exposure within 11 us.
However, the same thing does not occur when the camera is in the External Edge mode (EMD E). I send an external pulse (through ARDUINO too) and a message with an error appears: "Error 0xBFF60093 The serial read did not complete within the specified timeout period".
It is so strange. I think that the problem can be something in the attribute External Shutter Time - EST n (n can range from 1 to 93600 according to the camera manual). But, when I use the edit function at NI Camera File Generator for this camera, it says that this "n" ranges from 132 to 10005916.
Could someone help me with this issue?
Thanks in advance!
Fábio Machado Cavalcanti
Canada-Brazil Science Without Borders Student
Lakehead University, Thunder Bay, Ontario, Canada
Federal University of Pernambuco (UFPE), Recife, PE, Brazil
Undergraduate Student in Chemical Engineering

You need to verify what voltage the camera is expecting. Since you are using an Arduino, I will assume that your trigger signal is 5VDC. For a 12volt trigger, 5VDC would be right at the boundry of 0/1, and setting Level would trigger as the signal settles, presumably around 5.1VDC.
A pulse would never get there. If the camera does in fact need 12/24 VDC for triggering, you will need to build/buy a circuit for stepping up the voltage.
Machine Vision, Robotics, Embedded Systems, Surveillance
www.movimed.com - Custom Imaging Solutions

IPhoto library refuses to be recognized

I've moved to new iMac at work. Just transfered the iPhoto Library from the old multi-user machine (from my user window) via firewire. Put it in the pictures folder as a whole. (inside the folder looks good--things are still organized correctly)
Now when I open iPhoto with the option key held-down, I navigate to the pictures folder and iPhoto opens just a dozen or so of the +1,000 photos in the folder. It makes no sense to me where it got them, they were in the middle of all those year by year files.

I was hoping the database rebuild would trigger iPhoto to update the library to version 6. I don't know why, but it sounds like this library just hasn't been updated. Since the library structure is so different in v6, iPhoto can't read your v2 library properly.
We just need a way to trigger iPhoto to update that library. As I said before, you should get a warning that this is about to happen. The warning will indicate that once the library is updated it will be unreadable by previous versions of iPhoto.
As TD asked, is the v2 library still available on the old Mac? If so, you could move your broken iPhoto library (to the desktop or the trash) and copy over the v2 library again. Once copied to the new Mac, run BatChmod to correct permissions on the library folder. (I know it didn't make a difference before, but it could be the reason that iPhoto didn't update your library.) Then option-launch iPhoto, make sure it is pointed to open the new copy, and see if you get the warning that this library needs to be updated. If so, allow the update and see if all is well.
If you don't still have the old library available, someone very clever will need to come up with another way to trigger the update (if it is still possible). I wonder if you could do it just by moving the library around a bit. Like, move it to the desktop. Launch iPhoto and let it create a new, empty library. Quit, move the transferred library back to the Pictures folder, Option-launch and point iPhoto back to the transferred library, see if iPhoto wants to update it. A game of bait and switch.
If it's not possible to trigger the library update, you may be forced to manually create and repopulate your library. The second half of this technical artical tells how to do this while avoiding importing the thumbnails.
Edit: I just read your response to TD. It's great that you still have the old library. I suggest you try recopying, as I described above. [It's not about the library6.iPhoto file getting corrupted in the transfer, because the v2 library didn't have this file at all. The problem is the library not being updated to a v6 version when you first opened it on the new Mac.]

How to refer the trigger written in one form from another form ?

How to refer the trigger written in one form from another form ?
Thanks,
Ravi Shankar

Try to convert the PL/SQL code from Forms trigger into a PL/SQL library(.PLL),
and then attach that PLL in your forms.
Note that all Forms objects should be referenced indirectly, for example,
you have to rewrite
:B1.DEPT_CODE := :B2.DEPT_CODE;
:B3.TOTAL_AMOUNT := 100;
==>
copy('B2.DEPT_NO','B1.DEPT_NO');
copy('100','B3.TOTAL_AMOUNT');
This is the best way to share PL/SQL code among Oracle Forms.

Trigger&Gate Express VI. Is it possible to control Dialog Box parameters on the frontal panel?

When you use a Trigger&Gate Express VI the Dialog Box Options permits you to configure the VI. I am asking if it is possible to control Dialog Box parameters with controls on the Frontal Panel. I am especially interested on Start Level Threshold.

open the VI that the trigger and gate is in. Right click on the express VI and select open front panel. Then find the control that you want and edit the connector pane to be able to input the parameter that you want. Attached is a modified version that I came up with for you.
Hope this helps you.
Joe
Joe.
"NOTHING IS EVER EASY"
Attachments:
example_trigger_and_gate.llb ‏92 KB

Signal vs frequency measuremnt

Hi,
I am aquiring signal from DAQ board from three channel (Ch0, Ch1,Ch2). I want to measure the frequency of the Ch0 signal and plot it vs Ch1/Ch2 signal. I am sweeping the frequency in the channel 0 from 25kHz to 100KHz. I am using Labview s default 'tone measurement express vi' to extract frequncy of the Ch1 and feeding it as an X input in a XY plot. My Y input is a formula relating to the voltage of CH1 and CH2. But I am getting a moving point rather than a contineous plot in my XY plot. Can anyone help me. I have attached my vi.
Thanks,
prem
Attachments:
Frequency Domain DSR Measurement.vi ‏357 KB

Hi jibon,
Welcome to the LabVIEW forums!
I don't have the hardware you're using, so I cannot run the example VI you've provided, but it appears that you're using an XY graph inside a while loop- this means that the graph will be overwritten each loop. To preserve the previous data points, you'll need to use a memory structure of some type.
The simplest way to do this is with the Collector express VI (found in the Express>>Signal Manipulation palette) , but you might also want to try a shift register with a build array function:
This KnowledgeBase article and the examples it references might also be helpful- it has a few links to code that demonstrates using an XY Graph with a history:
KnowledgeBase 4TCFBDW8: How Do I Make an XY Graph Behave as an XY Chart?
http://digital.ni.com/public.nsf/allkb/18B56D8556D44BF18625753D006EFF7C
Hope that helps!
Regards,
Tom L.

6251 Counter input signal

Hello,
I am acquiring pulses which are 0-5V with the counter of the PXI 6251. However, I would like to know if it is possible to acquire pulses that are, for example 0-12V or 0-24V without damage the device. In other words, which is the voltage range for the counter input in a PXI 6251?
thanking in advance,
CJMV

Hi,
You will not be able to use the counter directly but you can setup an analog level trigger for your signals. This will create a pulse that isTTL compatible for you everytime the signal crosses a particular level. Then you can route this into your counter and perform any counter measurements on it. An example is this is shown here where it sets up a level trigger to make frequency measurements.
Alternatively you can purchase an industrial strength digital I/O board such as the USB-6525 but this does not include a counter.
Please let me know if this works out for you.
Message Edited by Abhinav T on 07-06-2007 05:20 AM
Abhinav T.
Applications Engineering
National Instruments India
LabVIEW Introduction Course - Six Hours
Getting Started with NI-DAQmx
Measurement Fundamentals

Trigger&Gate VI (Signal Manipulation Library)

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