Find frequency from input signal

Hi
How can i find frequencies from input signal (*.txt file) that consist of 7000 samples. I know the sampling rate.

This is a question about this thread.
I am working on a program to pull the two frequencies from a touchtone phone signal and figure out what number was pressed. I used the Spectral Measurements VI to perform an FFT on the data. I want it to work in real time, but I can't figure out how to get the max two frequencies out of the 2D array that is coming out of the Spectral Measurments VI. I am experimenting with the ptbypt functions, but can only get the single MAX value. I need to then compare these with a lookup table. Any ideas?
I am attaching the VI.
Thanks,
Eric
Attachments:
DSP FFT Sound Card AutoPower Spectrum.vi ‏133 KB

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Attachments:
pulse_PLL.vi ‏27 KB

Hi AnkitG,
Here are a couple of links that might help you understand a little more how the PLL work and a way to synchronize the task to perform a PLL.
http://digital.ni.com/public.nsf/allkb/07BC8D77D4E9AE258625708B007CE74F?OpenDocument
http://digital.ni.com/public.nsf/allkb/2F675A9F2162EA24862572570059A308?OpenDocument
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I hope, these examples might show you some useful concepts:
http://digital.ni.com/public.nsf/allkb/EBD603683446EC13862575B3006A63A2
http://digital.ni.com/public.nsf/allkb/9E71F8D7D3CD1B0886257688004AE353
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You can try to use Event structure and set to listen "key down" event.
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There are two pictures in attached file, 2.jpg will show you the detail.
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Attachments:
SpecialKey.zip ‏17 KB

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I receive data from MCU whcih sampling frequency is constant and we assumed it is S. now I get data from MCU with using VISA read block. I can display data, perform some functios like filtering, multiply and save them in txt files. all thing is OK.
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Hi
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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.
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Paul Falkenstein
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Hi all,
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Attachments:
heart sound analyzer.zip ‏257 KB

Hi Brett Burger,
Thanks for your reply. For your information, I have set the sampling rate as 10000 as for the sound format, I have set the bits per sample as 16 bit, the rate as 11025 and the sound quality as mono. I tried using your method by changing the sampling rate as 8K but still my program encounter the same problem.
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Heart Sounds1.vi ‏971 KB

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Hi Siva,
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public class firstLetter {
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Phase difference from 2 signals(HELP!)

Hi! I'm having trouble finding accurate phase difference between two signals.. one signal is from the input serial communication arduino and the second signal is a simulated signal. I want to find the phase difference between these two. I've googled a lot and found many similar threads of phase difference measurements, but it won't work.
The phase angle from the simulated signal is correct but the reading of the phase angle from the input signal keeps changing and I could not find an exact phase angle or phase difference.
What do you think I should do?

Doing phase difference measurements using two completely separate sets of hardware is in general a bad idea. You need to think carefully about how to synchronize the acquisition clocks of the computer vs. the Arduino. Better would be to measure your signal and generate your reference using one system, i.e. every time through the Arduino's outer loop, have it measure the voltage and also generate a reference level based on the internal clock, and transfer both to the computer.
That said, unless you know the signal frequency very precisely a priori, the phase difference between a synthetic reference and a measured signal will inevitably drift with time, at a rate proportional to the difference between the nominal and actual frequencies of the sample signal.

Estimating resonant frequency by sweeping the frequency from 100 Hz to 500 Hz

Hi
Actually, I need to do open loop system to vibrate the structure from 100 Hz to 500 Hz to find the resonant frequency. I have tried to build the code that can actuate ( excita) the structure and measure the signal fron the sensor ( capacitive sensor). Initially, I have tested my code by generating the signal from AI12 and connected that signal to the AO0 to evaluate the code. However, I have faced two problems. firstly, the stimulus signal in acquiring code (input) is delayed by around 20ms as can be shown in attached file. Secondly, generating signal is changing every 0.01 s where start from 100 Hz to 500 Hz. in other words, at the beginning i will have one cycle and the cycle will increase every 0.01s. My question, how i calculate the FFT for each 0.01 s and at the end showing the whole result in one graph to show the resonant frequency. Could you please help at this point.
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Khalid
Solved!
Go to Solution.
Attachments:
Untitled.png ‏78 KB
Add_1.vi ‏66 KB

Hi Nabilah,
Thank you again fro the the help. However, I have done what you have mentioned but i noticed in the FFT graph that estimate the frequency does not give me the right values. I have tested the code by generating the signal from AI12 and connected that signal to the AO0 to evaluate the code as can be shown in the attached file.the result what I expected from the code is to have the same amplitude at each frequency where I have connected the signal that generated from Ao0 to Ai12(channel). For example, if i run the code with sweeping frequency from 50 Hz to 500 Hz and amplitude 1 V, the result in FFT has to be at each frequency has the 0.7 amplitude (RMS).
Also, I have tried to understand the main function of Trigger.vi. Is this for detecting the signal from the input channel and generate signal as fast as possible?
I have attached modified code.
Khalid
Attachments:
photo.JPG ‏2350 KB
Synchronized AI and AO FRF.vi ‏43 KB

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
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Acquiring two input signals simultaneously

Hi,
I have an LVDT and a force sensor (both attached to a motor) plugged into my SC board and I am trying to read out & save the output data from both sensors simultaneously while the motor is in motion. The SC-2350 board is connected to the laptop via DAQCard 6036E . Two questions:
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Thanks for your help!
Thibault.

Hello Dani,
I assume, based on your position sensors and the image you posted, that you are using counters to acquire your data. Is this correct? If so, it is important to note that you cannot add multiple counter operations to a single task because they have different timing requirements and all channels in a single task must share the same timing and triggering. In fact, if you attempt to add a second counter channel to a DAQ Assistant for a counter operation, you will receive the following error when you try to close the configuration window:
So, you will have to use two different tasks to acquire your counter data. You can do this either by using two separate DAQ Assistants or by using two different tasks in the NI-DAQmx sub-VIs in LabVIEW. Since you are trying to compare the phase difference between the two measurements, you will also need to synchronize the operations so that you are reading from both counters simultaneously. There are several resources online which discuss synchronizing counters, and I have linked some that I thought might be useful below:
KnowledgeBase 1JPES6LL: How Do I Synchronize a Buffered Quadrature Encoder Measurement to a Signal
KnowledgeBase 3GGATSCC: Hardware Counter Start Trigger for Counter Synchronization
It would probably be easier to use the NI-DAQmx Sub-VIs to implement this synchronization because they give you more control over specific parameters of your task. You can use the NI Example Finder to browse some examples which use the NI-DAQmx sub-VIs for counters. You can open the NI Example Finder by going to Help>>Find Examples... in LabVIEW. Once in the NI Example Finder, you can find the counter examples by selecting the Browse tab and navigating to Hardware Input and Output>>DAQmx>>Counter Measurements; then you can select the Position category (shown below) to find the Position measurement examples.
Let us know if you have any other questions about taking position measurements.
Message Edited by Matt A on 04-09-2008 03:55 PM
Matt Anderson
Hardware Services Marketing Manager
National Instruments
Attachments:
Error -200147.jpg ‏32 KB
Example Finder Position.jpg ‏124 KB

Input signal not in range w1907

Input signal not in range hp w1907

Hello @daboxman,
Welcome to the HP Forums, I hope you enjoy your experience! To help you get the most out of the HP Forums I would like to direct your attention to the HP Forums Guide First Time Here? Learn How to Post and More.
I have read your post on how your monitor is displaying an error message: "Input signal not in range", and I would be happy to assist you in this matter!
I am providing you with some steps you can try below:
Step 1. Unplug the power cord from the back of the monitor and the wall
Step 2. Hold the power button down for at least one minute
Step 3. Plug the power cord back into the monitor and then into the wall outlet (not a power bar or surge protector)
Step 4. Press the Menu button on the monitor
Step 5. Navigate to the Factory Reset option and select it
Step 6. Try a different cable connecting your monitor to your computer
If the above steps did not resolve your issue you can try the monitor on a computer or other device to see if the issue persists. If the issue continues, please call our technical support at 800-474-6836. If you live outside the US/Canada Region, please click the link below to get the support number for your region.
http://www8.hp.com/us/en/contact-hp/ww-phone-assist.html
I hope this helps!
Have a great day
MechPilot
I work on behalf of HP
Please click “Accept as Solution ” if you feel my post solved your issue, it will help others find the solution.
Click the “Kudos, Thumbs Up" on the right to say “Thanks” for helping!

How I can measure frequency of TTL signal without external clock?

Hello,
I want to measure frequency of TTL signal using PXI-6254 or PXI-6713, without using external clock.
Frequency will be up to 100kHz. How I can use internal counter of 20MHz or 80MHz?

Hi Yuta K,
You have not stated what software you want to use for this measurement, but in case you're using LabVIEW, please go to the Example Finder (in LabVIEW go to "Help >> Find Examples").
In the Example Finder, you make sure the "Browse" tab is stil selected, and than you go to:
Hardware Input and Output >> DAQmx >> Counter Measurements >> Digital Frequency
Here you will find some good examples of measuring a digital frequency with 1 or 2 onboard counters.
If you need additional information, please let us know!
Best regards,
Peter S

Find frequency from input signal

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