Accuracy of frequency generation

Hi all!
I have a 6602 and wondering how accurate this DAQ card can generates a frequency of 432,292229547 Hz ?
Thanks in advance
Vu

Hi,
Using the 80 MHz timebase, you can get generate frequencies f_x = 80 MHz / i, i =4, 5,.....The closest you can get this devided timebase is 432.29 Hz I believe. The timebase stability is 50 ppm which means that the accuracy in this case would be +/- 0.02 Hz.
http://zone.ni.com/devzone/cda/epd/p/id/1170
Hope it helps.
Pelle S
District Sales Manager
National Instruments Sweden

Similar Messages

Using USB 6341 device for frequency generation but level is droped when conect

i am using USB-6341 Daq Device for frequency generation. The desired frequency is generated correctly but when i connect to other device the voltage level i means the Peak to Peak voltage of the frequency dropped to 0.6, 1 Volt and also the frequency fluctuated. As I disconnect it from the load or the device the frequency becomes constant and peak to peak voltage becomes 5.
Please some help me to resolve my problem.
Thanks
Best Regards
Naseeb
Solved!
Go to Solution.

Hi Nasib,
I just wanted to clarify a few more things. Can you answer the following questions?
What frequency are you trying to generate?
When there is no load connected do you see the desired frequency?
When the load is connected, does the frequency always change to the same value or does it fluctuate within a certain range? If it fluctuates, what is the range?
Also, what microcontroller are you using?
Can you provide any images?
Regards,
Travis Ann
Applications Engineer
National Instruments
Applications Engineer
National Instruments

Data acquisition and frequency generation togather with PCI-6251 and LV8.2

Hi friends,
I am a new user of Labview. I am using LB8.2 with PCI-6251 .
I have to generate frequency and then measure the data and then for next frequency and so on.
i know that for this i have to use looping and that is not a problem. The real problem for measurement is to identify whether the frequency is been generated. if yes then measurements starts otherwise it should wait until it started. then after finishing the measurements send a signal to generator for changing the frequency and amplitude.
Now these two things {generation and measurement} togather are not working correctly for me. so i make 2 diff file, one for generation and other for measurements <by modifying the examples>. I can run both file togather and it works. But it need lots off effort and time. I have to measure from 10Hz to 1000Hz in 2Hz frequency step and i cannt leave in between .
can anyone help me how to syncronize these two togather .
Trying to attatch. both the files here ..
main_v1.1.vi --> for Measuring
Oscilloscope.vi --> for waveform generation
Attachments:
main_v1.1.vi ‏150 KB
Oscilloscope.vi ‏37 KB

Hay thnx dude..
I found the example and now it works
once again thanks a lot

What is the accuracy of frequency measure with PCI 6023E?

I am measuring the exact frequency of 2.7Mhz signal. using PCI-6023E ,how can i calculate the accuracy of the measurments?

See
http://exchange.ni.com/servlet/Redirect?id=8437352
Regards
Filipe A.
Applications Engineer
National Instruments

Minimum Frequency for counter Pulse Frequency Generation

Hello,
What is the Minimum Frequency that the Counter Output Pulse Frequency VI can generate?
If I need to generate a REALLY low frequency pulse train can I do that?
Thanks
Dan

Hi Dan,
If you don't explicitly specify a timebase, DAQmx will choose a default depending on the initial parameters you set up for CO Pulse Frequency. For example, the following code should work on any DAQ device with a 32-bit counter and a 100 kHz timebase available (from my first post, 11.64 uHz is the minimum frequency in this scenario).
So... your 10-100 second periods should be more than achievable. The inverse of 12uHz is about 23.15 hours.
If you're on a 24-bit counter the maximum pulse width would only be ~167.77 seconds (2^24/100000), giving a frequency of about 2.98 mHz assuming 50% duty cycle.
The only way you should be getting an error at the 10-100 second durations that you are describing is if you start the task off at a faster rate (so DAQmx will pick a faster timebase by default) then modify it to output a lower frequency. Rollover times for the maximum default timebases are as follows:
    E Series:   ~0.839 seconds (24-bit counter, 20 MHz timebase)
    M Series:   ~53.69 seconds (32-bit counter, 80 MHz timebase)
    X Series:    ~42.95 seconds (32-bit counter, 100 MHz timebase)
If you want to set a different signal source as a timebase, you can do it with a DAQmx Channel Property Node:
I'm afraid I don't really understand what you are trying to do specifically. How does this "infinite" pulse length fit within the context of your application? Why not simply write the line high in software? What hardware are you using?
Best Regards,
John Passiak

MyDAQ frequency generation beyond 20 kHz

I am looking into purchasing a myDAQ, as we use LabVIEW at school and my job. I noticed the frequency generator only goes up to 20 kHz. Is this a limitation of the hardware or the student software? If it is merely a software limit, would the full version circumvent this limitation? I am interested in producing frequencies of at least 50-100 kHz.

Hey bentwookiee,
The myDAQ analog output hardware is capable of outputting 200 kS/s per channel. Depending on the type of signal you want to generate the maximum output frequency will be something less than that, and I think the pre-built FGEN code supports a maximum frequency to 20KHz to ensure enough samples per period to generate a good signal.
Thanks!
-Sam K
LabVIEW Hacker
Join / Follow the LabVIEW Hacker Group on google+

Constant frequency generation

hii....
i want to generate constant frequency of 5kHz (2.5 Vrms) using some ni module......actualy i want to energize accelerometer (hbm b12) using 5kHz (2.5 Vrms) supply.
plz help me out !!!!!!!!!!!!

Hello Prashant,
To get 5KHz Frequency your sampling rate of the signal must be double or grater than double. So now you have to generate/acquire a signal on 15000 samples/sec. You can go with high resulation cards depend on you channel count. If channel is less or for your learning you can configure M series 6255 card in MAX and configure it.
Thanks and Regards
Himanshu Goyal | LabVIEW Engineer- Power System Automation
Values that steer us ahead: Passion | Innovation | Ambition | Diligence | Teamwork
It Only gets BETTER!!!

Pulse generation PCI-6220

Hi there,
I´m an absolutely newbie to labview and hope to get some advices as I´m completely stuck at the moment.
I´d like to generate variable TTL pulses to 3 different lines. Since the PCI6220 card only has two counters I´ve to go for the normal hardware correlated DIO lines.
For now I´d be happy to see it working just for one line as follows:
__| |________| |_ ...
I´ve to be able to set the pulse width of the high time for the first and the second pulse as well as the two different low times. This scheme should furthermore than be repeated n times. Thus having 5 variables, the length of the pulses in ms: 'Low1','High1','Low2','High2', and the number of repetitions: 'n'.
I may be horribly wrong with this, but I think working with the duty cycle doesn´t work for that application, does it?
Assuming I use the frequency generation of a counter as a sample clock to my pulse generation, it seems rather simple taking for instance 'High1' corresponding pulses of the counter clock to generate the 1st pulse then 'Low2' pulses for the subsequent low pulse and so forth. Could anyone give me a hint to do so, or are there better/other ways how to achieve this? Are there eventually vi's available I could start with (haven´t found proper one´s in this forum nor in the Labview implemented library)?
Many, many thanks in advance for any help!!
Robert

Rob: I looked at your example earlier when I was near my LV machine. From memory:
1. I think I recall that you specified PFI 2 as the sample clock source for the digital task while using CTR 0 to generate the clock. According to this doc, the default output pin for CTR 0 is "terminal" 2. However, that does NOT turn out to be another name for PFI 2. Rather, terminal 2 is designated as PFI 12 as can be seen here. (This stuff is also visible in MAX when you select your device, right-click and choose "device pinouts").
2. I recall you used a U32 array version of DAQmx Write. You may need to use the U8 version on your 6220 board. Also, the init values you wrote before the loop alternate between 255 (all bits high) and 0 (all bits low). The values you write inside the loop alterate between 1 (LSB high, all other bits low) and 0 (all bits low).
3. You defined the digital task for finite generation, filled its buffer before the loop, then attempted to keep overwriting it inside the loop. These are not mutually consistent. If you want finite generation, fill once only. If you want continuous generation, it'll take some care not to overwrite too soon.
4. Minor nit: It may not matter in your app, but often its best to start up the digital task before starting the counter task that generates its clock. You can accomplish this by simply routing the error cluster from the digital task's DAQmx Start up to the counter task's Create Virtual Channel.
I'm not near LV now to look at the recent example from Christian M. Hope it suits your needs...
-Kevin P.

Frequency sweep with DAQmx

The following is the setup :
LV7.1 + PCI_6229 + WIN_XP
For controlling the drive rpm of a servo motor, I need to generate a range of frequencies from 60 to 2500 at 10 Hz intervals.
With the DAQmx polymorphic VI, "CO Pulse Freq" , I can generate a particular frequency.
But if I have to change it on the fly how do I do it ? Like ideally if
there was a property node for the polymorphic VI (!) , I could easily
do it. But it does not have one such node for frequency and hence the
query.
Having started the frequency generation at a default value, I would
like to alter it programmatically without having to stop the VI and
reload the fresh frequency.
Any suggestions welcome.
Thanks
Raghunathan
Raghunathan
LV2012 to Automate Hydraulic Test rigs.

Hello SG_ENGINEER,
So that is possible, but it is a completely different approach than that mentioned above. You would have to use a continuous analog output program and change the output waveform. Check out the attached example. I modified a shipping example to do an analog output and increment the frequency of the output waveform.
-Alan A.
Attachments:
Continuous_Analog_Out_Update_Sinewave.vi ‏100 KB

How to avoid jitter in analog output(square wave) generation

Hi all,
Iam working with PCI-6723 32 channels analog output,iam generating a square wave,sampling at 100ks/s.
ican able to generate upto 10kHz square wave.The wave form appears clean when it is below 1000Hz if i crossed 5KHz to 7KHz, iam getting jitter in the output square wave form,i have experimented with the digital filter but still the jitter is persisting,
since iam using 12 channels for such similar generations so i have fixed the sampling rate.100Ks/s.
kindly suggest me how to avoid this jitter in high frequency generation.
OS::WINDOWS 2000
HARDWARE PCI-6723.
I/O CB 68
NIDAQ:7.3
LABVIEW 7.1
kindly find the attached file.
Thanks and Regards
RAJESH
Attachments:
Untitled.vi ‏73 KB

Hi ALAN,
Thanks for your reply, well the square appears to be overlapped ie one ON/OFF period another waveform tries to overlap, actually i planned to take a snapshot of my oscilloscope (tetronix) but since its not advanced one ,i have attached the file kindly look into it,you can observe the at some higher frequencies there is lot of difference between rise time and fall time.
Thanks and Regards
rajesh
alan actually iam decorating my front pannel do u have any sample layouts for coloring ,buttons kindy forward me .
Attachments:
Doc1.doc ‏56 KB

Inaccuracy problem in MT Phase Locked Loop VI

Hello,
I'm using MT Phase Locked Loop VI(PLL VI hereafter) in LabVIEW with NI USRP2920(Kind of IQ converter) to measure carrier frequency and phase of input signal.
The PLL VI works fine when relatively low frequency signals like 500Hz are input, but when it comes to high frequency like 30kHz, the accuracy of frequency and phase estimation in PLL VI is significantly degraded. In my implementation, MT Baseband PLL is selected as an instance.
Can anyone describe why this things happen?
If it is difficult to measure high frequency with this PLL VI, does anyone know appropriate way to measure input IQ signal's carrier frequency and phase?
Thank you for reading through.
P.S.
In my implementation, FDMA is adopted. So, above "carrier" means kind of subcarrier which is downconverted to the baseband as IQ.

Aha! I found a solution! For future people looking for the answer - I highly recommend THIS link as a set of files that will get you 90% of the way there
https://decibel.ni.com/content/docs/DOC-1121
For people still reading - the difference is see in my attached JPG. The top example (mine) uses a multiply followed by a low pass filter. The problem is that that filter is non-monotonic with changing phase (i.e. that filter's DC output is maximum when phase is matched but decreases with both leading and lagging phase). The NI solution (bottom) is monotonic with phase (that is, phase difference between the LO and the input).
I can tell the NI solution is doing some complex (as in non-real numbers) math to extract the phase information. It looks a lot like in-phase & quadtrature extraction and maybe thats important. The key question I have going forward is - what does a blessed Hilbert Transform help me with ? What is its function? Reading the help - I do get a little buried in the Math of it.
-Thanks
Attachments:
ExampleCode.jpg ‏60 KB
PLL_Test2.vi ‏88 KB

PXI 6733 smallest voltage for external reference?

Hi, I need to know, what is the smallest voltage possible for external reference?
I couldnt find this information anywhere, I just found, the internal reference is 20Vpp and the device is 16 bit, so the LSB is 312uV.
If I connect the EXT_REF with smaller voltage, let say 5V, the reference becomes 10Vpp and the LSB becomes 156uV.
What is the smallest voltage that I can use, in other words, what is the smallest LSB I can get with this device?
regards,
yan.

In prinziple you can decrease the external reference as you wish. But be aware of the error margin you create.
You can see in the following graph that the measurement error consists of three parts, which have different reaction to the range:
It all ends up to the following equation:
You can see that the gain error (the first part) is only half the equation to finding the actual accuracy of the generation. So, assuming that we have zero temperature drift, if we can greatly reduce our gain error by providing a highly accurate reference signal, then we are still left with the offset error that is independent of the reference signal.
You will also add additional error margin by using the external source, which ofcause has to be calibrated separetly, and adds an additional voltage drift. I therefor would recommend not to use reference voltages below 0.5V.

Ni 6602 Card, Configuration in Register Level Programming

Hello,
I want to do register level programming with the NI 6602 card .
I want to use an x4 encoder reader and I want to use the continuous
frequency generation.
so i got the following tool to map the kernel space to the user space, so
a simple shell script will do the job.
http://www.linux.it/~rubini/software/phob/phob.html
and than just using the provided function phob_io
to programm the registers in a shell script:
#!/bin/bash
# shell script for init 6602 card with prf and encoder counter
# set prf
../phob_io ''0:048=0000'' # Input Select Register
../phob_io ''0:00C=1109'' # Command Register
../phob_io ''0:038=00ffffff'' # Load A Register
../phob_io ''0:03C=00ffffff'' # Load B Register
../phob_io ''0:
034=9218'' # Mode Register
But don"t get any output as i expect, what is wrong?
Do i have to set some othe registers, or write somthing to the PCI-Config?
Does anyone has some sample configuration?
Thanks
Mario Behn
Mario Behn
Microwave Remote Sensing Laboratory Room 104
University of Massachusetts
Knowles Engineering Building
Amherst, MA 01003-4410
phone (413) 545-4675
fax (413) 545-4652
email [email protected]

A typical project for one of the 660x RLP examples needs to include the following source code files:
../OSinterface/osiBus.cpp - generic register I/O interface used by the example code
../OSinterface/Linux/osiUserCode.cpp - OS specific adapter used by osiBus to access registers on the hardware in the specific OS
../ChipObjects/tTIO.cpp - abstraction of the chips and registers on the hardware into C++ classes and properties
and one of the examples files, e.g.
../Examples/gpct_ex1.cpp - implementation of a specific operation, including all initialization of the hardware
(The same is true for the examples for other boards although the names of the ChipObject and examples will be different.)
Each of these files needs to be compiled to give y
ou object files, and then all of the object files need to be linked together to build an application (executable binary). The errors you list seem to indicate that you are not using all of these files.
There is more information on the RLP example architecture in the attached PDF document.
Christian Loew, CLA
Principal Systems Engineer, National Instruments
Please tip your answer providers with kudos.
Any attached Code is provided As Is. It has not been tested or validated as a product, for use in a deployed application or system,
or for use in hazardous environments. You assume all risks for use of the Code and use of the Code is subject
to the Sample Code License Terms which can be found at: http://ni.com/samplecodelicense
Attachments:
Register_Level_Programming_Architecture.pdf ‏165 KB

Should PFI I/O Be Set To A Default Setting Before Use?

Hi everyone, I am using the PFI lines on my PXI DAQ Card (6229) for Counter Output frequency generation and Counter Input frequency readings. I know these lines on power up of the PXI card are set to high impedance mode by default. Should these lines be set to digital LOW '0' before setting them up for Counter Output or Counter Input use? Is it good practice to set up the PFI lines to a default state before using them in an application?
Thanks!

Hello testdesign,
Thank you for your inquiry. You do not need to set the PFI lines to any specific value before setting up a Counter Input or Output task. The LabVIEW Example Finder has excellent Counter Input and Output examples if you have any questions on how to program or set up these tasks. These can be found by going to Help » Find Examples » Hardware Input and Output » DAQmx » Counter Input or Counter Output.
Cameron Schaefer
Applications Engineer
National Instruments

NI-DAQ 6036E

I need help ASAP and would appreciate it very much if someone could help me out.
I need to develop a small application that needs to generate a sine wave and output it to a 6036E.
I am trying to use the express vi that generate a sine wave and feed it into the another express vi that outputs it to a 6036E.
The application is needed as a controller for a sensor. The scope of the project is to have an input voltage come in and compared to the sine wave generator and based on some criteria the sine wave generator will output a voltage so that it can control the sensor.
A reply or some sample vi would be greatly appreciated. I checked the sample vi within LabView and none conform to what I am looking for.
Thank you.

Hi!
The PCI-4472 is an 8-channel dynamic signal acquisition device for making high-accuracy audio frequency measurements. It does not have any Analog Output channels.
If you need to generate an output signal at high speeds I recommend using any of our high-speed sources. You can find detailed information about them at our Products and Services website for Signal Generators.
Please let me know if you are interested in getting any of these devices.
Regards,
Tica T
Applications Engineer
National Instruments

Accuracy of frequency generation

Similar Messages

Maybe you are looking for