AO squarewave with 1 microsecond pulse width
Im trying to create a squarewave with a pulse width of 1 microsecond and a period of 2 microseconds (50% duty cycle). So far I have been trying to use what code i can get off the NI site to help me with this, but so far no luck. I have a PXI-6025E running off the PXI-8176 controller. Can anyone point me in teh right direction? Or possibly if theres a VI I skipped over that might have the answer.
Thanks,
-Mark
Mark,
There is an example which ships with LabVIEW titled "Function Generator.vi". You may also find this on our website at the following link.
Simple Function Generator Example
http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?p_guid=B45EACE3D82956A4E034080020E74861&p_node=DZ52311&p_submitted=N&p_rank=&p_answer=&p_source=External
Change the waveform type on the front panel to Square Wave. If you wish to change the duty cycle, from the default of 50%, then you will have to go to the block diagram and set the % duty cycle input of the Compute Waveform VI in the middle of the diagram.
This example will work with any E Series device, which includes the NI 6025E. Keep in mind that a period of 2uS is an output rate of 500kHz. The NI 6
025E only has an analog output rate of 10kHz. You will need to consider different hardware if you wish to achieve an analog output frequency of 500kHz. However, if your square wave is TTL (0V and 5V) then you should just use your board's counters. They will be able to perform this frequency generation easily.
DAQ-STC: Generating a Continuous Pulse Train (Intermediate-Level VIs)
http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?p_guid=B45EACE3EB0B56A4E034080020E74861&p_node=DZ52328&p_submitted=N&p_rank=&p_answer=&p_source=External
Regards,
Justin Britten
Applications Engineer
National Instruments
Similar Messages
-
Hello
I just have a few questions.
I am using the NI 6034E DAQ board in order to
generate simultaneouly 3 different TTL digital signals, with different
pulse width, and output these TTL signals to an external circuit that I
am using for this application.
The following pattern of the TTL pulses will look like this:
01010101 01010101
00110011 00110011
00001111 00001111
From
what I understand, I have to use the 2 counters, Ctr0 and Ctr1, to
generate the TTL pulses that I desire, because the DIO lines are
software timed only and I will not be able to produce a deterministic
output period using these DIO lines. Am I correct? Also, do I have
to use a separate counter to generate a separate TTL digital pulse. I
need 3 different TTL pulses and there are only 2 counters for this DAQ
device. The three generated TTL signals will be feed to an external
circuit. Concerning the hardware connections for my application, I
assume that the generated TTL signals will be output from
GPCTR0_OUT(pin 2) for counter 0 and GPCTR1_OUT(pin 40) for counter 1
of the NI 6034E. Is this correct? Is there any way that these TTL
signals can be output from three DIO lines(DIO0...2).
Here is some code that I plan to use in order to do this:
#include <NIDAQmx.h>
static TaskHandle gTaskHandle = 0;
DAQmxCreateTask ("", &gTaskHandle);
DAQmxCreateCOPulseChanTime (gTaskHandle, "Dev1/ctr0", "", DAQmx_Val_Seconds, DAQmx_Val_Low, 1.0, 2.0, 2.0);
DAQmxCreateCOPulseChanTime (gTaskHandle, "Dev1/ctr1", "", DAQmx_Val_Seconds, DAQmx_Val_Low, 3.0, 4.0, 4.0);
DAQmxCreateCOPulseChanTime (gTaskHandle, "?????", "", DAQmx_Val_Seconds, DAQmx_Val_Low, 7.0, 8.0, 8.0);
DAQmxCfgImplicitTiming (gTaskHandle, DAQmx_Val_FiniteSamps, 5);
DAQmxStartTask (gTaskHandle);
DAQmxWaitUntilTaskDone(gTaskHandle)
DAQmxErrChk DAQmxStopTask(gTaskHandle)
DAQmxErrChk DAQmxClearTask(gTaskHandle)
I believe this code should generate the 3 TTL square waveforms that I want for my application.
Please provide me with some feedback. It would greatly be appreciated.
Thank YouHi,
The NI 6034E is a multifuntion DAQ device, this means you have:
(2) counters
(8) DIO lines (software timed)
(16) AI, single ended
(0) Analog Output
You have a couple choices here:
1. Software timed digital output of all three signals, max 1khz loop rate, non-deterministic.
2. Hardware timed digital output of 2 signals, max 20Mhz.
3. Hardware timed digital output of 2 signals and software timed digital output of 1 signal.
4. Find another NI MIO board such as the NI 6251. This board will do 10Mhz pattern generation for (8) DIO lines.
For the hardware connection, you are correct, the output for the counters will be taken from pin 2 & pin 40. Here's the pinout for the NI 6034E for reference:
The output of the Counters can be routed to some of the PFI's or to the RTSI connector. You can see this in MAX
Message Edited by Matthew W on 11-19-2007 01:24 PM
Attachments:
2007-11-19_131609.jpg 61 KB
2007-11-19_132435.jpg 86 KB -
How to generate a pulse train with different pulse width and delay?
How to generate a triggered pulse train with different pulse width. for example, after each trigger signal, let's say 2 ms, then the counter output a pulse with pulsewidth of 1 ms, and then after 3 ms delay after the first pulse, the second pulse was generated with a pulse width of 4 ms. Next cycle when the trigger signal comes, the same two pulses will be generated and so on. Is it possible to achieve this by using 6601 counter card? and if yes, how to achieve this? Thanks!
Unfortunately you can not create a hardware timed pulse train with different widths on each pulse from a counter. Whilst it can be changed on the fly using software, since you require a hardware triggered signal getting the software involved will not give a huge amount of accuracy when the pulse will actually change.
So in short you can't use your 6601 card (or a counter timer) to achieve this
There are three possible Alternative solutions
1 You could use a high speed digital IO device such as the (6533/34) to generate your variable signal which would require setting up the pulse train as a series of states based around the burst transmission mode where the clock would give you your specific timing.
2 A timed analogy output (for example on a MIO card with a clock (PCI-6220 / 62xx), i.e. Not the 6704 style static analogy output cards)
3 A high speed digital waveform card such as the (, 656x , 655x, 654x, 6534, 6533 (http://www.ni.com/modularinstruments/find_right.htm) ) this could then be scripted to work with your triggering and also there is a digital waveform editor which will enable you to set up the pattern you wish to generate (http://sine.ni.com/nips/cds/view/p/lang/en/nid/13555)
Hope that helps
Tim Matthews
NI (UK) -
How can I create a pulse train with varying pulse widths?
I'm trying to create a finite pulse train that varies its duty cycle. I was hoping there was a clever way to do this neatly. I've attached a very rough picture of the train I'm hoping to make, with the pulse widths defined with t, the delay between pulses d, and a total of N+1 pulses. Thanks!
Edit: My current method is to use the pulse train function, and actually create 2N+1 pulses, stacking the "double length" pulses.
Attachments:
ExPulseTrain.png 9 KBI wound up just building the first short pulse, and then the train of longer pulses, and sticking them together. I attached a screenshot of the code I went with.
Attachments:
VarPulseTrain.png 29 KB -
Finite pulse train with variable pulse widths
Greetings LabVIEW developers,
Does anyone have code that can show me how to use E-series counters to generate a finite pulse train where the individual pulse widths vary? I need to generate a series of 20 pulses with the high time for each pulse randomly varying between 50 and 1000 microseconds. The low time for each pulse needs to be constant (around 50 microseconds).
Thanks,
Ryan WrightRyan,
Sorry, but this isn't possible with the counter/timers. I've been wanting this capability myself for about 6 years now.
Personally, I think it's an unfortunate "hole" in product capability. The other major data acq hw allows you to capture and later replicate a signal of interest. You can capture an analog waveform with AI and later play it back with AO. You can capture a digital pattern and later play it back with timed DIO. You can capture buffered semi-periods with a counter -- but you can't play play them back later. So for your app, you'll need to generate the variable freq using timed DIO. The new M-series boards ought to work for this, or a dedicated high-speed digital board.
There's another product that I think is even better for timed DIO though and it's put out by one of NI's "Alliance partners" -- Viewpoint systems. Here's an example of why I like it. Let's say you need to generate 20 pulses within 60 seconds. The times of the pulses need to be precise to within 1 usec, and they have no common divisors. The NI method will require you to use an update rate of 1 MHz and you'll create a buffer of 60 MB to represent the digital pattern at every usec. The Viewpoint method needs a buffer of 40 entries. Each entry is a combination of a timestamp and a pattern to generate at that timestamp. That pattern will just stay there until the next defined timestamp. So all you do is define the digital pattern at the instants when one or more bits will change. It works analogously for digital input - if you capture with 1 usec resolution for 1 minute but there are only 20 pulses (40 digital transitions), you only capture the 40 relevant timestamps & patterns instead of a full 60 MB.
If interested, look for the PCI-DIO64 at Viewpoint's website.
-Kevin P. -
In Delayed Pulse Generation vi,Problem With THE PULSE WIDTH??
In Delayed Pulse Generation vi, I want to input a very low number for the Pulse Width while using an external timebase source. But the minimum pulse width has to be 2. Does anyone know how can I solve this problem??
Hey 45,
Unfortunately, there is no way to generate a pulse width smaller than 2x your external timebase.
There is an option to create a pulse of arbitrary width of your external source if you can afford some software processing in between. What you can do is use 1 counter to measure how many source edges of your card's internal timebase (80 MHz for TIO only, 20MHz or 100kHz for TIO and STC) your external signal is. This uses pulse width measurement as the counter application. Once you know how many source edges it takes to represent your pulse, then you can use triggered pulse generation and use the internal timebase with the pulse specs set to create the exact pulse width you want (and delay) and you can use your external pulse as the trigger. Th
is works well if your pulse is always the same width and you can measure it before hand. As an example, let's say your pulse is 20 internal timebase pulses when measured. This means you can use the pulse specs to specify a pulse width of 0.75 your pulse width by using only 15 internal timebase edges for your pulse width.
I don't know if I was clear above or not but if you give me your exact application you are looking to achieve, I might be able to help you out. Hope that helps.
Ron -
Hello Friends,
I am new to Labview. And now I am working on a project where I have to measure the pulse width.
I have attached a pulse waveform and would like to measure the pulse width of the first rising the falling edge and log it , rest of the signal I am not interesed in.
I will have this signal 6 times on my digital/analog input.
Can someone help me with the pulse width measurements.
Thank you.
Kind Regards,
Attachments:
Pulse width.PNG 60 KBI get this pulse ( as in picture attached), I want to get it on analog or digital pins in such a way in get the pulse width of only 1st edge.
And this 1st edge lenght is different then the rest that follows. I would like to have the pulse width for only the 1st edge and log the width.
And similarly this signal will come from 5 more different sources. So each signal is different.
For now i connected it to AI0 and I can see the signal.
1) next step measure only the first edge.
2) 6X input channel
2) log it.
Attachments:
Pulse width.PNG 60 KB -
External sample clock with pulse width measurement
Dear all,
I am using a NI 6220 board (programming with ANSI C) and would like to perform a "single pulse-width measurement" using an external gate signal and an external signal as source.
Using the "DAQmxCreateCIPulseWidthChan" command the program and card works only partly as intended. Namely, the external gate did work, but the card uses the internal 80 MHz time base signal instead of the external source connected to the default source pin (PFI 8).
I tried to route another PFI pin to the default source pin using the "DAQmxConnectTerms" command but this did not help either.
Obviously, I am missing something...
Best, Uli
Solved!
Go to Solution.Hi Uli,
I posted to your thread here.
Best Regards,
John Passiak -
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,
MartienTo 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 -
In the DAQmx 9.4 Readme the following is stated:
Samples Not Acquired on NI 660x or NI 6624 Devices When using pulse width, semi-period or two-edge separation buffered measurements with the NI 660x and NI 6624 on counters 0 and 1, some samples may not be acquired under certain circumstances.
Could anyone elaborate on this? I am particularly interested in knowing under what circumstances this problem arises for the 6602 PCI devices.
How should I understand 'NI 660x and NI 6624 on counters 0 and 1'. Is it only a problem on counter 0 and 1 for the 660x or does this only apply for the 6624 devices.
/molaAre there any NI Product Support Engineers out there who has an answer to this question and who are willing to share it with me?
-
Single Pulse Width with External Clock
I am trying to setup a 6602 counter for a single (non-buffered) pulse width measurement with an external clock. Under normal testing, the unit under test will provide the pulses, I need to measure the number of pulses during different time periods (1, 60, and 300 seconds). I want to do a pulse width measurement and I'll supply the gate signal pulse to the counter for the specific time needed.
Under normal operation, the unit under test is wired into the counter's source and the pulse is wired into the gate. For testing purposes I am using a BNC-2121. I have the counter's source wired to the Adjustable Square Wave Output and the gate wired to the Trigger output.
Here is my C++ code. I am getting a timeout error on the read and I don't know why. Any help would be appreciated.
//Create Task
DAQmxCreateTask( "task1", taskHandle );
//Create Pulse Width Channel
DAQmxCreateCIPulseWidthChan( taskHandle, // TaskHandle
szCtrName.c_str(), // Counter Name
"", // Channel Name
dMin, // Min Value
dMax, // Max Value
DAQmx_Val_Ticks, // Units
DAQmx_Val_Rising, // Gate Edge
"" ); // Scale Name
//Set the Pulse Width Terminal to the gate signal
DAQmxSetCIPulseWidthTerm( taskHandle, // TaskHandle
"", // Channel
"/CTR2/PFI38" ); // Terminal
//Set the Timebase Src to the counter's source
DAQmxSetCICtrTimebaseSrc( taskHandle, // TaskHandle
"", // Channel
"/CTR2/PFI39" ); // Terminal
//Start Task
DAQmxStartTask( taskHandle );
//***Send pulse to gate counter***
//Read Counter
DAQmxReadCounterU32( taskHandle, // Task Handle
DAQmx_Val_Auto, // Num Samps to Read
10, // Timeout
ulBuffer, // Read Buffer
1000, // Buffer Size
&lSampsRead, // Num Samps Read
NULL ); // ReservedI've setup a pulse width task in NI-MAX using the onboard clock and everything worked fine, so I know the hardware is working.
My unit under test is providing the pulses (from gyros) I need to measure. The pulses indicate the position of the unit so there are X, Y and Z axis gyros. I need to measure these pulses for specific periods of time (1, 60, and 300 seconds). For example during the 1 second measurement, the X and Y gyros should measure zero pulses and the Z axis should measure 515 gyros. During a 300 second measurement the X and Y gyros should measure < 60 and the Z axis should measure 30800.
So the gyro pulses are wired to the counter input and I am using a DIO channel from NI-6508 to provide the gate pulse. The gate signal will be high for either 1, 60, or 300 seconds depending on the test. The gyro pulses are essentially the external clock to the counter. I want to count the gyro pulses during the pulse of the gate (DIO).
To simplify the setup, I connected to BNC-2121 directly to the card. I have the adjustable clock output going to the counter input of ctr0 and the trigger signal going to the gate of ctr0. Once the task has been started and before the read ( I had a breakpoint set in the code), I would press the trigger button on the BNC-2121 and hold for approx. 1 second. I then execute the Read statement, and I always get a timeout. From my experience working with NI, I'm guessing I don't have a channel property set correctly, but its not obvious to me and I can't find an example to do exactly what I'm trying to do.
The CTR2 designation in the code was the object name of the card. I have two 6602 cards in my chassis. I was using ctr0 of the second counter card, so PFI38/39 was correct.
Again, any help would be appreciated. -
Pulse width measurement with MultiQ
I am trying to measure the pulse width of a signal with my PC, and I
just have Quanser multiQ PCI board that can do A/D,D/A,timer, encoder,
can any one tell me how can I do it? do I need to use the labview ?
thanks,
ClarkI looked at Quanser's web site and couldn't find any specs on the board so I hope you have the information to answer the question. If the board has counter timer circuitry, then you could use that depending on the width of the pulse, the accuracy of the daq board's clock, and the resolution that you need for the measurement. If you just have the A/D to use, then it might be possible to acquire a signal with the pulse in it and then use software to analyze the acquired waveform data and calculate a pulse width. Again, it would depend on the acquistion rate of the board and the pulse you're measuring. A narrow pulse with a slow acquisition rate is not a good combination. What software you use is optional. If Quanser provides a software utility that can do it a
ll, use it. If Quanser has a LabVIEW driver, than that would work too. If my answer seems a little vague, it's because you need to provide a bit more information. If no else chimes in with experience with Quanser boards, the best for a detailed answer would be Quanser. -
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 KBWhat'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 -
Pulse width modulation with daq mx
Im trying to change the pulse width modulation on the fly with daq mx. All I have found so far are examples useing traditional DAQ, but not DaqMX. It would be a lot easier if I were to use DaqMX since I will be useing other daq applications in my program and would rather use mx.
Does this help?
Attachments:
PWM-Counter_Output_Folder.zip 63 KB -
I'm using the NI PCI-6025E card connected to an SCB-100 wiring peripheral. I'm programming the DAQ card using LabVIEW 6.0.2 on a win95 box.
My first attempt has yielded some surprising results.
I created a vi with a single while loop set to true. Within that while loop is a two frame sequence. Both frames use the "Write to Digital Line.vi".
The first frame sets the line in wire to false.
The second frame sets the line in wire to true.
The device channel on both frames has been set to my user defined channel nam
e -> clock.
clock --> sets the DIO0 channel to be digital write out.
Using an oscilloscope and some wires I hook ground to the SCB-100's digital ground and I hook the probe to the DIO0 channel. What I see are two different pulses alternating between one another. One has a pulse width of 5ms and the other has a pulse width of about 50ms. You seem to get a grouping of one type of pulse followed by a grouping of the other type of pulse.
Obviously this is very strange and not what I want. It is also far too slow. So I'd like to know if anyone knows how to do this properly. Remember I only need a low pulse width of 0.5 microseconds.
Thanks,
Any help or guidance would be much appreciated.
ScottScott,
You don't need to use a digital line to create a TTL pulse. The PCI-6025E has two onboard general purpose counters. You can use one of these counters to create a single pulse of the desired pulse width. For an example of how to program the counters on your board, refer to LabVIEW's Search Examples>>I/O Interfaces>>Counters>>Pulse Generation>>DAQ-STC based.
The advantage of using a counter over the digital line is that it allows you to control the timing of the pulse through hardware and not software. Thus, it is inherently faster, and the timing resolution is more accurate. The counter will count down an internal 20 MHz timebase to create the pulse delay and the pulse width.
For more information on the hardware capabilities of your board, you can refe
r to the User Manual online at www.ni.com/manuals.
Hope this helps.
Regards,
Erin
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