Looking for VI to measure pulse-width on a waveform

does anyone know of a VI to measure the pulse width of a pulse trace in a waveform?

The examples to look for would be located under the DAQ >> Counters examples, and you would probably be looking for anything using the DAQ-STC chip (which is the counter chip on our E-Series board). Advanced examples that are in addition to the shipping examples can be found by searching the website as well.
Jim Cahow
Applications Engineer
National Instruments

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Measure pulse width of signals generated by DAQ

Eventually, I would like to:
Start a counter pulse width measurement and analog out at the same instant.
Stop the pulse width measurement with an external digital signal.
My current plan is to use a digital out on the DAQ to go to a digital input and the counter start input. The digital input will be a start trigger for the analog output. This works, except for the counter.
While trying to implement this, I tried a simpler test of just generating a digital pulse with the DAQ and wiring that to the counter inputs. That doesn't work, even though it looks fine on an oscilloscope. Then, without changing the software at all, I connect a function generator to my counter inputs, and it measures pulse widths flawlessly.
I'm actually implementing this with a Python wrapper around the DAQmx C API, but I recreated it in LabVIEW, and it behaves the same. VI attached. I have the latest DAQmx drivers.
Attachments:
meas_pulse_width_simple.vi ‏32 KB
screenshot.png ‏99 KB

ColeTrain wrote:
apaulsen,
Just a
friendly heads up, but this is more of a DAQ post and you will
generally get more replies to these types of questions by posting in
the proper forum.
That being said, try taking a look at
the Example Finder and look under the DAQmx examples at
synchronization/multifunction as this would be a good place to start
working on what you're trying to wind up doing down the road.
I am actually the OP. apaulson is my coworker, and he was logged in to the forums on the workstation from which I posted.
I
realized that it ended up in the LabVIEW forum, so I reposted on the
DAQ forum:
http://forums.ni.com/ni/board/message?board.id=40&thread.id=7185.
I understand why there is a search-to-post policy, but it's rather
unintuitive and clunky, and I got confused. IMHO, ubuntuforums.com
does this the right way and automatically searches before you submit
your post.
Anyway, I figured it out. See the other post for solution.

Measure Pulse Width and Period Statistics

Hello,
I'm trying to solve what should be a very simple problem. I would like to measure common characteristics of a binary analog voltage input, pulse width and period. The canned pulse width/duty cycle/period VIs and express VIs use a histogram or peak to peak method on a set buffer size of data and produce one output. I would like to measure these signal characteristics over a long period of time and collect statistics on pulse width and period data (max, min, median, mean, standard deviation, etc.) to indirectly measure the eccentricity of a system. Although I am relatively inexperienced in LabView scraping off a considerable bit of rust, I did not think this task would present a challenge, but I have been stumbling around for a couple of days trying to create an array of output parameters such as pulse width so that I may calculate the statistics on all measurements.
If anyone can step me through some of the thought process to a solution or show me how to format data collection so that this can be done, I would very much appreciate the help.
Thanks,
Evan
Attachments:
Example.jpg ‏194 KB

Hi Gena,
I am assuming you are using the DAQmx drivers in LabVIEW for your
PCI-6014. Avoiding a While loop may be difficult if you need to
perform this measurement many times and you might not know when the
signal is going to begin. Without a While loop, you'll have to
set up your timeout period long enough so the pulses will begin before
your VI stops.
With this in mind, you may want to look at some of the shipping
examples with the DAQmx driver. You can find these in LabVIEW's
Help menu by going to Find Examples. For measuring the pulse
width, browse the folders in the Example finder by going to Hardware
Input and Output>>DAQmx>>Counter Measurements>>Period
or Pulse Width. In this folder, there is the Meas Pulse Width.vi,
which measures the pulse width once and stops. You should be able
to take the pulse width measurement you get from here and check to see
if it's in your range, then output a pulse on the other counter if it
is in the range. The pulse output examples can be found in
Hardware Input and Output>>DAQmx>>Generating Digital
Pulses>>Gen Dig Pulse.vi.
Thaison V
Applications Engineer
National Instruments

Measure pulse width and generate pulse depends on the width

Hi,
i have a serias of pulses ... 600 micro,30 micro,30 micro (around 10 times) ........ nothing for 1 mili second ..
so i need to generate a pulse after the first pulse arrives ... (its width around 600microSecond)
1. use the first counter to measure the pulses ...
2. if arrived pulse ... 500microSecond<the pulse width<700microSeconds .... then generate pulse with second timer ....
the problem is that i dont want to use the while loop inside the labview ...
can i programm the counters to make the width calculation and if the width is bigger to generate trigger to the second counter .... ?
the hardware is 6014 sample card ....
thanks
gena
(see attached)
Attachments:
F0087TEK.JPG ‏27 KB

Hi Gena,
I am assuming you are using the DAQmx drivers in LabVIEW for your
PCI-6014. Avoiding a While loop may be difficult if you need to
perform this measurement many times and you might not know when the
signal is going to begin. Without a While loop, you'll have to
set up your timeout period long enough so the pulses will begin before
your VI stops.
With this in mind, you may want to look at some of the shipping
examples with the DAQmx driver. You can find these in LabVIEW's
Help menu by going to Find Examples. For measuring the pulse
width, browse the folders in the Example finder by going to Hardware
Input and Output>>DAQmx>>Counter Measurements>>Period
or Pulse Width. In this folder, there is the Meas Pulse Width.vi,
which measures the pulse width once and stops. You should be able
to take the pulse width measurement you get from here and check to see
if it's in your range, then output a pulse on the other counter if it
is in the range. The pulse output examples can be found in
Hardware Input and Output>>DAQmx>>Generating Digital
Pulses>>Gen Dig Pulse.vi.
Thaison V
Applications Engineer
National Instruments

Measure pulse width with 4 counter simultaneously

Hello,
I am using NI PCI-6601 measure the pulse width with 4 counter simultaneously, due to only a DMA channel on this card so I selected interrupt data transfer mode to read data from PCI bus for 4 counters, but it working only for few seconds then a error message prompted:
Error -200141 occurred at DAQmx Read (Counter 1D DBL 1Chan NSamp).vi
Measurements: Data was overwritten before it could be read by the system.......(See attached picture: TestUI and Error MSG.bmp)
I know the problem caused due to system is unable to read back data from PCI6601's memory as fast as they card countered. My quesition is:
1. The timebase is 20Mhz(Sample rate), how to change the sample rate slower (like 100Khz) ?
2. Any good solutions can meet my requrement?
Attached is my source code, Test.vi is the main VI.
Thanks for your help.
Steven
Attachments:
Test.zip ‏557 KB

What's more, you could include four channels in one task, so you don't need to build four task!
Attachments:
4 counters in one task.png ‏719 KB

Can counter measure pulse width difference between two signals

I am interested in determining the high pulse width time that two signals have when they are in various phases between eachother.

Why don't you try one of the pulse width examples. I don't know what ADE you are using, but you can search for examples (http://www.ni.com/devzone/dev_exchange/ex_search.htm) with the key words "+pulse +width" and find several examples in different languages. This will measure the pulse width of one signal, but you can program most of the counters to do multiple tasks at the same time. Just copy the code twice and change the counter number to program counter 2 as well. If you want the ORed pulse width time, I would recommend adding a OR gate to your circuit and then feeding that into a counter.
I hope this helps.
Joshua

I am having data i want to measure pulse width without using hardware and tell me how to start and stop soft timer using labview

soft pulse width measurement

If you are creating a pulse in software somehow, then you can use Pulse Measurements.vi that's on the Analyze>Waveform Measurements palette. This will require that the input is of the waveform data type with signal and timing information. There's several timing functions on the time & Dialog palette that you could probably use. Check out Tick Count and Elapsed Time. If you could provide more details on what exactly you need to do, we could provide more help.

Measure pulse width cont - failure in example? NI-DAQmx

Hello!
I tried the "PulseWidth-Buff-SampClk-Cont.c"-Example. I got the following error:
DAQmx Error: Invalid timing type for this channel.
Property: DAQmx_SampTimingType
You Have Requested: DAQmx_Val_SampClk
You Can Select: DAQmx_Val_Implicit, DAQmx_Val_OnDemand
Task Name: _unnamedTask<0>
Status Code: -200300
Here is the Example-Code:
#include <stdio.h>
#include <NIDAQmx.h>
#define DAQmxErrChk(functionCall) if( DAQmxFailed(error=(functionCall)) ) goto Error; else
int main(void)
    int         error=0;
    TaskHandle taskHandle=0;
    int32       read;
    float64     data[1000];
    char        errBuff[2048]={'\0'};
    // DAQmx Configure Code
    DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
    DAQmxErrChk (DAQmxCreateCIPulseWidthChan(taskHandle,"Dev1/ctr0","",0.000000100,0.838860750,DAQmx_Val_Seconds,DAQmx_Val_Rising,""));
    DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"/Dev1/PFI0",1000.0,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000));
    //DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"/dev1/PFI13",1.0,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000));
    //DAQmxErrChk (DAQmxCfgImplicitTiming(taskHandle,DAQmx_Val_ContSamps,1000));
    // DAQmx Start Code
    DAQmxErrChk (DAQmxStartTask(taskHandle));
    printf("Continuously reading. Press Ctrl+C to interrupt\n");
    while( 1 ) {
        // DAQmx Read Code
        DAQmxErrChk (DAQmxReadCounterF64(taskHandle,1000,20.0,data,1000,&read,0));
        printf("Acquired %d samples\n",read);
        fflush(stdout);
Error:
    if( DAQmxFailed(error) )
        DAQmxGetExtendedErrorInfo(errBuff,2048);
    if( taskHandle!=0 ) {
        // DAQmx Stop Code
        DAQmxStopTask(taskHandle);
        DAQmxClearTask(taskHandle);
    if( DAQmxFailed(error) )
        printf("DAQmx Error: %s\n",errBuff);
    printf("End of program, press Enter key to quit\n");
    getchar();
    return 0;
What could i do?
Thanks
Andreas

The help says this:
Sets only the number of samples to acquire or generate without specifying timing. Typically, you should use this function when the task does not require sample timing, such as tasks that use counters for buffered frequency measurement, buffered period measurement, or pulse train generation.
So this line is only needed for specific applications. The counter has no sampleclock, like the analog input or the analog output, so you can not use this, but have to use implicit timing instead.
Hope this helps!
André

How do I measure pulse width in VeriStand 2010?

I'm using an NI PXI-6229 M Series DAQ.
I the channel set up in System Explorer and I have my input signal routed to the Gate of Counter 0. When I deploy and open the Workspace the measurement says 0 seconds although an oscilloscope shows a 7ms square wave at the terminal.
I think the problem may be that I don't have a timebase applied to the Source of Counter 0. How do I put an internal timebase on the Source? I would prefer to do so without changing any VIs and I definitely don't want to add an external frequency generator to my setup.

I think that the gate terminal cannot be used in that case. You might want to try to connect the external signal to the input terminal of the counter.
Once you have rewired the external connection you will notice, that NI VeriStand might not update the frequency that often. NI VeriStand doesn't measure the frequency/period by using a frequency task. We have used a simple edge counting task that takes the upper and lower limit of the frequency to determine the update rate of the frequency value. The more accuarate the settings are, the higher is the update rate. In order to get a feasible update rate, increment the lower limit to a value that will never be below the real minimum frequency of the external signal and set the upper value to the maximum expected frequency.
Thanks,
Tom
http://www.newgistics.com

I'm looking for code to measure SNR, SNDR, etc. using Measurement Studio, Visual Basic.

I've collected audio ADC data and wish to measure signal-to-noise, frequency, amplitude, etc. I'm using Measurement Studio with VB.

Frequency and Amplitude should be easy to measure. The CWDSP frequency domain processing methods perform transformations between the time domain and frequency domain and perform analysis in the frequency domain. Slightly more difficult is the measurement of SNR. I would recommend the following tutorial:
"The Fundamentals of FFT-Based Signal Analysis and Measurement in LabVIEW and LabWindows" available here. This page also links to a LabVIEW example, which can be used to understand the dataflow and functions necessary to create the system.
There is also a good signal to noise ratio tutorial here.
regards,
Eric Meyer
Applications Engineer
National Instruments

Analog pulse width measurement

Hi, I have a signal that is a number of single pulses which i am capturing using a Digitizer and then fetching integer values to make the pulsewidth measurements faster.
My signal is AC coupled therefore i have quite a lot of noise, i want to measure the pulsewidths but i need some hysterisis to reject any of the noise. I am a C programmer and this would be a simple case of looking forward a number of elements in the array after the initial threshold has been satisified but i do not know how to do this in LabView.
Can anybod help me out?
Thanks.
Wayne

There are many ways to detect the pulse width of a signal with noise and without knowing your setup how the signal looks it, we will be totally guessing. That being said I would first try the "Measure Pulse" function under the Waveform Measurement palette (does your C have that?). If the signal for some reason won't work with this canned function then by all means write your own. Set up a comparision to say is my analog value greater then 0.5V? (or what ever) then find the times from going from FALSE to TRUE to find the rising edge, and from TRUE to FALSE for a falling edge.
Unofficial Forum Rules and Guidelines - Hooovahh - LabVIEW Overlord
If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.

Pulse width measurement with FieldPoint CTR-502

I would like to measure the pulse width of a signal (ranging from 10 ms to
400 ms out of a signal with period width of about 1 second). I would like to
use a fieldpoint counter module FP-CTR-502. I could find examples on how to
measure frequency but I did not know how to alter it in order to obtain the
pulse width.
Thanks,
Martien

To measure pulse width of a fixed-period signal, you only need to use one counter, so the configuration and program would be different than the frequency measurement example. Set the count source for counter 0 to "32kHz Reference" and the gate source (and wire your signal) to "Gate Input 0." You'll also need to create a control channel to reset counter 0 (as described in the frequency example).
Your LabVIEW program should run as follows:
- When Gate Input 0 becomes true, do nothing
- When Gate Input 0 becomes false again, read then reset counter 0
- repeat
You can use FP Advise to wait for the gate to change (just like the frequency example).
Once you have the number of counts, you can divide that by the frequency (32 kHz) to calculate the "on tim
e" (pulse width) of your signal.
Regards,
Michael Shasteen
Applications Engineering
National Instruments
www.ni.com/ask
1-866-ASK-MY-NI

Triggered single pulse width measurement

I am trying to measure the width of a single pulse, but would like to use the pulse itself as the trigger for a counter input pulse width read using a PXI-6608. I would like to do this since the pulse can come at any time (much longer than any practical timeout) and I would like to avoid having to place a DAQmx read in a while loop waiting for the pulse to appear. Also, while the pulse is high, I would like to produce front panel feedback (light a boolean indicator). I seem to be able to achieve that by using a digital input line, but again requires a DAQmx read in a while loop. I haven't had much experience with triggers and my attempts so far appear to seem like triggers are not compatible with counter input pulse width measurement. Is it possible to set up a trigger for a pulse width measurement?

Hello kayotik,
I think the best thing to do here is to use separate while loops. You can put most of your code in a main while loop, and then put your DAQmx read in a separate while loop. Both loops can run in parallel (just don't wire any outputs of one while loop to the other while loop, because then one will become dependant on the other). In order to pass data between the two loops, you will need to use a local variable. The DAQmx read can write to a local variable, and the main loop can read from that local variable.
You will also need to stop both loops with a single stop button. This article shows how (and also demonstrates the use of local variables to pass data between independent while loops):
http://digital.ni.com/public.nsf/allkb/267704CDE91156D186256F6D00711AAE
Colden

NI 9401 pulse width measurement.

Hello,
I'm not sure I fully understand the pin-out diagram. At present I have a NI9401 in a NI 9172 chassis.
DIO0 and DIO1 are connected to light gates. I have an opto switch and I want to measure the pulse width when an object blocks passes through the slot. Can I use any of the other free input to do this?
Free inputs are, DIO2, DIO4 and DIO5.
The other I/O pins are being used as triggers.
Cheers
K
Solved!
Go to Solution.

Hi Daisy,
If you open your DAQ Assistant properties, and read the Measuring Pulse Width help on the side, you'll see that "You can use the counters on your measurement device to measure pulse width. Pulse-width measurements measure the time between either a rising and a falling edge, or a falling and a rising edge." If you change the Pulse Width Setup Starting Edge setting to Falling edge and look at the picture above, you'll see that the pulse width it's measuring the width from a falling edge to a rising edge (the pulse width while the signal is low). So this measurement will go from the falling edge of your first measurement to the rising edge of your second measurement. If you want to measure the width of the first pulse (while the signal is high) you need to set your Starting Edge to Rising.
Do you know whether the width that you want to be measuring is while the pulse is high or while it's low? Starting Edge Rising and Starting Edge Falling should give you different measurements, because they're measuring different things. You should verify which result it is you want, and what it is you're trying to measure.
Hope this helps!
Emily C
Applications Engineer
National Instruments

When exactly do pulse width measurements start?

I am using a PCI-6601 to measure pulse width and period of a PWM signal in LabView (DAQmx).
I use ctr0 for the period and ctr1 for the pulse width. The period is measured between falling edges. As I am interested in the high pulses, the pulse width measurement is configured to start with a rising edge.
I do a buffered measurement with continuous samples.
I use a common start trigger (ArmStart) for both tasks.
Everything works just fine, but one thing puzzles me:
My start trigger can occur at any phase of the PWM signal, so I expected the first measurements to be invalid. This is true for the period measurement, but the pulse width is always correct. It doesn't matter in what phase my trigger occurs, the first reading of the pulse width is always correct.
Can someone tell me why?

This is speculation, but it's probably just that NI decided to follow slightly different rules for pulse width measurement than for some of the other counter measurements.
I've done triggered period and semi-period measurements before, but don't know that I've done triggered pulse width or frequency measurements.
For the two former cases, I know that the counter will start counting time immediately after the trigger edge. The first measurement represents the time from the trigger to the first active edge period (or semi-period) edge. It is often meaningless as you anticipated. For pulse widths, I suppose NI simply decided that the trigger will arm the counter but you also need the pulse's leading edge before you start counting to measure pulse width. So the first measurement is a true measure of pulse width and is never meaningless.
If this is true, then it may be tricky to sync / correlate the data in simultaneous measurements. For your particular app, you could get away with performing a single semi-period measurement and then calculating the periods and pulse widths. In other apps, it could get more difficult.
-Kevin P.

Looking for VI to measure pulse-width on a waveform

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