How do i measure the frequency of a sine wave using a field point counter module

I need to measure the frequency of the sine wave using field point. is it possible and if yes how. do i need to convert the sine wave signal to square wave. Please let me know.

It probably would be easiest to convert the sine wave to a square wave with a simple external circuit and then use a counter module to measure the frequency. There is a shipping example in LabVIEW that shows how to measure frequency with a FieldPoint Counter module.
JRA

Similar Messages

How can I measure the frequency of an analog signal?

Hi, I am trying to measure the frequency of VAC signal coming from a gas turbine engine at my university. If I can get the values of frequency, I can determine the speed (RPM) of the engine. I am fairly new to LabVIEW and I have been looking through manuals like crazy in order to find out how to obtain the frequency. I have measured the signal with an oscilliscope and the highest frequecy will be about 1.5kHz. I am currently using a USB-6218 and it can collect the voltage signal with ease, but it won't give be analog frequency so simply. Can anyone explain a way for me to obtain the frequency values? And if you could show or tell me in a very simple way (because I am not very fluent in LabVIEW yet), that would be amazing! Thanks!

Check this out:
Attachments:
RPM.vi ‏17 KB

How can I measure the frequencies of two analog input signals simultaneously?

Hi
I have two AI signals, and I need to determine the frequencies of those signals. The frequencies range from 1-125Hz. I currently have a VI where I can sample one of the signals for 1 second (sampling at 300 Hz for 300 samples) and determine the frequency.
I need to read two signals at the same time and get both of the frequencies at the same time, but I can only figure out how to read them individually, so I can read one signal, then one second later I read the second one, then I read the first one again, then the sceond one, etc.. How can I read two signals simultaneously?
Thanks
Attachments:
FreqMeas11.vi ‏41 KB
FreqMeas11.PNG ‏18 KB

"at same time", this depends on the hardware, you can do as has been previously stated just set up a 2 channel acquisition and you will get 2 sampled waveforms back. Most hardware A/D as multiplexed and true simultaneous sampling is not done. At 125Hz this is not an issue unless you are interested in very small phase changes between the samples. just keep this in mind if you are expecting samples to be completly synchronized.
Paul
Paul Falkenstein
Coleman Technologies Inc.
CLA, CPI, AIA-Vision
Labview 4.0- 2013, RT, Vision, FPGA

How Can I Measure the CPU Power My Flash Movie Uses?

Hi All,
I'm working on a complex job that is intended to play on low-end PCs so I'm looking at ways to reduce the processor load the movie needs to play. Obviously large screen size, high frame rate, intensive ActionScript, and complex graphics all add greatly to how much CPU power is needed to run a Flash movie, but is there a way of getting an accurate reading of the CPU power it is using? I am modifying a job that was running badly on low-spec PCs so now want to adjust it to run faster and smoother so would like to somehow be able to compare the modified job with the original. Any Idea how I could do this?
Any help would be greatly appreciated.

Hi. I tried your suggestion and I could not get it to work well. In
fact it worked better without the running average (which suprised me).
I also played with the number of data points but still could not get it
to work well.
Do you have any other suggestions on how I could sort this problem out?
I
have attached a screen shot of the signal. To recap, I'm trying to
measure the'y' position of the flat regions of the signal. The signal
does not have a constant level, so this 'y' position varies with time
in a non-unform manner.
I am currently differentiating
the signal and selecting the y position when the differential is equal
to zero (within a tolerance band).
In the screenshot, the
signal has been zeroed using the method I have described above.
However, it occasionally has glitches which may be caused when the code
picks up a zero gradient at a peak or valley in the signal.
I therefore need some kind of algorithm that only measures the position of the flat regions.
Many thanks
John
Attachments:
screenshot.gif ‏121 KB

Measuring Superimposed Frequencies on a Sine Wave

Hi,
Just looking for advise on the best way to measure superimposed frequencies on my raw data. The raw data (voltage versus time) is ultimately a noisy sine wave with a frequency of 1Hz. I need to determine where the noise is coming from, i.e. is it vibrational, electrical or surrounding noise, hence requiring the frequency of the noise if possible.
Any advise on the best way of filtering the data would be appreciated. Currently I am using a butterworth filter with a cutoff setting of 1.5Hz. The original data was sampled at 1.5KHz so the noise was measured and so could be filtered during postprocessing.
Also when filtering I don't want to loose important data i.e. sudden peaks or drops.
Regards,
John.

John,
Have you tried spectrum analysis of your data? That will give you the frequency content of the signal plus noise. One peak will be at the 1 Hz sine signal and other peaks will correspond with the supeimposed signals. With a 1.5 kHz sampling rate you would get information on frequency content up to the Nyquist frequency of 750 Hz. A peak at 50 or 60 Hz will likely be power line frequency interference. Gears, bearings, and motor armature slots produce characteristic frequencies which are related to the rotational speed.
Lynn

How can I calculate the frequency of a 2-4Hz three phase sine wave in 50msec?

I want to calculate the frequency of a sine wave using either all three phases or just one, but I want to know the frequency after 50 msec, I don't want to have to wait for a full period.

I have a mathematically sound suggestion but I do not know how well it will work in application. Most period measurements measure the time between a full period or several periods to eliminate the error introduced by the measuring device. Essentially the device error is made insignificant.
Mathematically you can do much more but there is a tradeoff between recording less information and knowing (or assuming) some values. For instance, if one knew the amplitude and could calculate the derivative of the signal, one could calculate the frequency. A sine wave can be represented by the function: A sin (BX)=C , where A is the amplitude, B is the frequency, C is the present measured value. If the equation is solved for X, we get: X=(sin^(-1)(C/A))/B. The d
erivative of the first equation is AB cos(BX)=C. If the equation for X is now substituted into the second equation, we get, AB cos(B (sin^(-1)(C/A))/B)=C. Solving for B we get B=C/(A cos(sin^(-1)(C/A))). Remember, we already know A and C, so we are done.
Practically every step and assumption in the above argument introduces possible error which will affect the accuracy of the frequency. Unfortunately it is a trade off and that is why at least a whole period needs to be measured to get an accurate frequency.
Jeremy Braden
National Instruments

How to get a pulse output at the start of a sine wave which is the input?

i am working on a comparator that generates a pulse for the positive cycle of a sine wave.but i want to get a pulse of shorter duration at the start of a sine wave (using labview) please suggest

Hello;
You can synchronize one of the general purpose counters your board have to the analog input operation. By doing that, you can have your analog input starting the counter operation which will generate the desired pulse. Moreover, you can even specify the delay and width of that pulse. For more information on how to synchronize DAQ operations you can refer to an Application Note named "Advanced Synchronization Techniques for Data Acquisition" which can be found at our web site.
Hope this helps.
Filipe

How to measure the frequency of the data plotted on the waveform chart

i have made a virtual instrument in labview that acquire data (say sine wave) into a spreadsheet file and also on the chart from the function generator. I measured the frequency of the data from the chart but it is coming out to be very less. How can i calculate the frequency of the plotted sine wave and also from the spreadsheet file.

If you want to get an idea of the base-frequency of an periodic signal, you can measure the number of samples in between two maxima or in between two minima of the periodic signal.
Multiply the number of samples by the sample-interval (1/Fsample in [sec]) gives you a rough estimate.
FFT, I mentioned is one of the more advanced calculation-methods.
The method calculates the spectrum from a waveform.
Hope this helps,
Patrick

How do I make a VI to measure the frequency and power level of a transmitter using the NI 5660

I am working on an RF project that requires me to measure and record the frequency and power level of a transmitted signal. I am using the NI 5660. I am quite new to Labview and the PXI, so I'm not so sure how to do this.
I know I have to initialize the NI 5660 but I don't know what to do afterwards in terms of measuring the frequency of the acquired signal. I'm not sure what blocks to put together nor do I know where to find them. could someone please enlighten me on how I may understand what I need to do.

Hi princess! (it's funny writing that somehow)
Have you considered the example finder?
There should be examples on how to acquire and measure with the NI 5660.
And there should be a block in LV that was delivered with the NI 5660 software, that does something like "acquire spectrum" or something like that.
Regards,
Pattos
LabVIEW Gretchin

How do you find the frequency of a small sample size and a square wave.

I am collecting data from ten 12v pulses that are seperated pretty uniformly. The pulses make a square wave. I need to know how to input this small sample size and find it frequency. I need this frequency to be output in a readable file. Im not very knowledgeable in labview so if you try and help me please be very descriptive.
I know i need some sort of trigger because of uknown wait times before the sensor will be triggored but other than that im pretty lost. Any help would be appreciated.

What have you tried so far? What parts are giving you trouble? Please be as specific as possible. Post the code you have written.
You ask about frequency measurement and then you are talking about triggering.
If you always have 10 pulses, just measure the time from the beginning of the first pulse to the beginning of the last pulse. The frequency is 10/time.
Break down the problem to smaller parts. Acquire the data. Measure the frequency. Save the result to a file. Get each part working separately, then put them together.
Lynn
Sorry about duplicate post. My internet connection is very slow today.
Message Edited by johnsold on 05-31-2010 12:05 PM

I need to measure the frequency of a signal on Pin 39 (PFI 15) of a PXIe-6361 module.

I need to measure the frequency of a signal on pin 39 (PFI 15) of a PXIe-6361 module. All of the digital I/O pins are already assigned and in use. The signal frequency range is 50KHz to 500KHz. I have tried all of the sample programs for DAQmx Counter/Timer frequency measurement. If I modify them to use my hardware, I get run-time errors with conflicts with resources already assigned.

Hi Julia,
Thanks for the response. As I stated before, I have tried all of the examples available that apply. There are only three and one of those uses two counters. The two I have tried are:
Examples/Hardware Input and Output/Counter Measurements/Digital Frequency/
DigFreq-Buff-Cont-ExtClk-ArmStart.prj and
DigFreq-LowFreq1Ctr.prj
These examples default to using what appears to be traditional DAQ hardware (Dev1/ctr0 and /Dev1/PFI0). I changed the counter to mine (/PXI1Slot3/ctr3) and directed my signal source (PFI15 on pin 39) to the counter. No matter what I tried would not run. They would always compile but gave run-time errors ranging from resources already in use to “external trigger required”. I have no external trigger source and, if I did, there is no indication of how to assign it to the counter. NI has a very good X Series Users Manual that tells all of the great things you can do with the hardware, but there is NO CLUE how to do any of those things!!!! I know that some NI DAQmx functions use hardware resources that they never tell you about. I discovered that when trying to produce a single output pulse from a timer using counter #0. (Which, by the way, no one at NI could tell me how to do it.)
Measuring frequency should be very simple. The unknown signal is routed through a precise gate to a counter, and then the counter is read. NI DAQmx uses the opposite approach of using my signal as the gate and counting their internal source. However, the examples would not let me use the internal reference sources.
To answer your other questions, I am not performing any other measurements at the same time and the counter is not being used for anything else, period.
Any help would be greatly appreciated. Thanks again.
Wayne K.

Wiring a SCB-68 to measure the frequency of a TTL pulse signal

Sorry if this is a basic question but could someone please help me and tell me how to wire up a SCB-68 connector block (connected to a AT-MIO-16 DAQ board) so that I can measure the frequency count of a series TTL pulses (signal from photon counting). At the moment I don't understand how the PFI1-9 connections are related to the GPCTR0/GPTR1 counter connections on the block and how they're all realted to the source,gate and out 1-5 connections on the DAQ board.
Ultimately I want to be able to put this measured frequency into a Labview program with a controllable gate period.
Thanks in advance
Nick

You might want to search the Knowledge Base on the NI's Support Pages for "Cable Mapping for a 68 Pin Connector to a 50 Pin Connector". This should take you to a link that will explain the mapping of a 50way to 68way cable and subsequent lines you are looking for ( reference sub link 68F50M), I guess you have SH6850 cable connected from the AT-MIO16 card to the SCB-68.
Please check out the information about the pin outs, that should help you work out which pins map to the counters, eg GPCTR0_source would be pin 37 on your SCB-68
Regards
Joe (NI)

Can I measure the frequency from all PFI pins?

I am using a PCI-6229 DAQmx card. I am trying to measure the frequency from pin PFI 5. I have been successful in measuring frequency from PFI0 and PFI1 but for some reason I am not able to measure on other pins. When I run the run the DAQmx Read sub VI it times out like it is not reading anything. I am using the same sub VI I created to measure 5 as I did 0 and 1 so I know that the VI is working. What is the matter? Are there only certian pins that I can measure? Would the sub VI time out because there is no signal on the pin?

Hello Flowserve1,
Thanks for your post!
The basic answer to your question, "Would the sub VI time out because there is no signal on the pin?", Is yes if there is no signal coming into the pin your are bring a signal in on. It sounds like you were able to do a "frequency" measurement on PFI0 and PFI1? Usually the counter tasks are used for such a measurement. How are you performing these frequency counter tasks on your PFI lines? It looks like on the pin read out that PFI0,1 and 5 are for digital tasks and PFI routing lines. Are you internally routing your signals to other places? If you want to measure the frequency using counters, this board has two of them so use Ctr 0 and 1 gate or source to make these measurements. Let me know if any of this helps you and perhaps you could post a piece of your code that you are using to make your frequency counts.
Cheers!
Corby_B
http://www.ni.com/support

How can I measure the hertz in a wave form?

How can I measure the hertz in a wave form?

As an example, this is from BBC Technical Requirements for HD material:
3.1.1 Stereo line-up tones
All stereo tracks must use EBU 1KHz tone (left ident). All tones must be sinusoidal, free of distortion and phase coherent between channels.
Digital Audio Reference level is defined as 18dB below the maximum coding value (-18dBFS) as per EBU recommended practice R68.
See also:
http://www.bbc.co.uk/guidelines/dq/pdf/tv/tv_delivery_to_network_programmes_v1.2-2011.pdf
for full document.
And for BBC Radio:
Not every Network requires tone. Check the delivery requirements with the commissioning network or click here.
Reference tone, where used, should be at -18dBFS or PPM 4 on A, B and/or M.
If submitting material with reference tone, tone and programme material must be have been monitored and measured through the same technical chain. The level of the tone must be equivalent to 0dBu and no less than 8dB below peak audio level for the programme material.
THE LEVEL OF TONE MUST HAVE A KNOWN RELATIONSHIP WITH THE LEVEL OF THE PROGRAMME MATERIAL AND THIS MUST BE STATED; for example: “Tone at 8dB below peak programme level”.
As a newcomer to digital sound (my background is camera) I confess to being somewhat confused. We are normally told to record at the highest level possible. So for voice podcasts I tend to record at about -6dB below peak for maximum volume, distributeds on MP3 files.
But I can underatand that televison and radio especially for analogue transmission) may have limited headroom, hence the requirement for -18dB peak = 0dBM.
I remember when we first rented out Digital Betacam cameras, some recordists were recording almost everything OVER -18dBM.
I suspect that until we have an all-digital world, these requiremnents will still be in place.
Many thanks to all. It's a ghreat community!
Brian Rose

Measure the Frequency Of User Report Running

Hi Experts,
Currently I am working on the BW3.5 version. Currently we are having 70 reports in the system. Our client requirement to list out the reports which is not executed frequently and label that obsolete.
So I want to find out how many times a particular query has been accessed.Unfortunately, the BI statistics cube are not activated in the current server. So I cannot utilize the BI statistics cube option.
I tried working with ST03N as well with table RSDDSTAT but didn't get a clear picture. I am still amazed how people find this mode useful to gauge the frequency of use. Probably I am not interpreting the data well. Would preferably like to know who have used a particular query on a particular day.
Please through your thoughts on the issue. Thanks.
Thanks,
RR
Edited by: Ragu R on Oct 7, 2010 1:39 PM

Hello Nacho,
the output terminal of the AI Start VI will never be able to give you the actual rate when you use external clocking. It's only valid whenever you use internal clock (and the board divides down the master clock to get as close as possible to the desired rate). This is what you get at the output.
You can test this by using an example with internal clock and choose a "rare" frequency/rate such as 1621.5. The board will really sample at a similar rate, but not always at the exact speed you may choose.
If you want to calculate the frequency, you'll have to use counters and feed the encoder signal (CH A) to the counter's source (or gate depending on which method you use to compute the frequency).
Regards,
Jorge M.

How do i measure the frequency of a sine wave using a field point counter module

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