Measuring frequency question

I have a Speedmaster device that outputs a TTL signal at a frequency
related to the measurement that it is reading. The frequency
fluctuates around 8000 Hz. I am trying to measure the period between
pulses in real time using a counter on a 6024E DAQ card but I am
getting readings that are not correct. I connect the +output of the
Speedmaster to the Counter0 Gate the GND output of the speedmaster to
the DGND of the DAQ. I am using the 20MHz timebase to count pulses on
Counter0. This is my first time trying to measure frequency this way
and any help would be appreciated.
Thanks,
-Mike

Hi Mike,
Gabi’s suggestions are definitely good ideas. If you are certain that your Speedmaster device is generating a TTL signal, you can check to see if your signals are connected properly using MAX.
1.
-Open Measurement and Automation Explorer.
-Right-click on the 6024E and select “Test Panels…” Test Panels are useful for trouble shooting because it removes any LabVIEW code from the test. You can use the digital I/O tab to see if you are switching the digital value. You can use the counter I/O tab to see how many pulses are counted.
-To configure the Counter I/O test, under Channel Name, select whichever counter you are using (zero or one).
-Change the Mode to “edge counting”.
-Select your signal channel as the “Edge Source”. The signal channel for your device (assuming you are using counter 0) should be PFI 8.
2.
There are several examples for acquiring frequencies in LabVIEW. These are accessible in LabVIEW by selecting Help>>Find Examples…
Then browse to Hardware Input and Output>> DAQmx >> Counter Measurements >> Digital Frequency. The appropriate example for your application would be “Meas Dig Frequency-Low Freq 1 Ctr.vi”.
3.
For simple acquisition tasks, it may be easier to generate your own program using the DAQ Assistant.
-Place a DAQ Assistant on the Block Diagram and choose Acquire Signals>>Counter Input>> Frequency.
-Select your device and counter.
-Configure your Signal Input Range. You mentioned that your input will be around 8000 Hz.
-Your Measurement Method should be “1 Counter (Low Frequency)”.
-For acquisition mode, you will probably want to use either “N samples” or “Continuous”.
-“Samples to Read” will be determined by how many pulses of which you want to measure the frequency. You may want to measure the frequency of a large number of pulses and average them to get one value.
-Click “OK”.
-On data output terminal of the DAQ Assistant Express VI, right-click and select Create>>Indicator to create a graph of the measured frequency.Message Edité par The Fearless Hyena le 04-30-2007 06:05 PM

Similar Messages

  • Measure Frequency C#

    Hi,
    There was a question posted earlier asking about measuring frequency using C# and a multifunction DAQ that got my interested in th e topic.
    I found this example using a counter but it throws an error at startup.
    https://decibel.ni.com/content/docs/DOC-16563
    There are 2 tasks, an AITask and a counter task.
    The error occurs when trying to setup the input frequency terminal.
    counterTask = new Task();
    counterTask.CIChannels.CreateFrequencyChannel(counterComboBox.Text, "",
    Convert.ToDouble(minValueTextBox.Text),
    Convert.ToDouble(maxValueTextBox.Text), edge,
    CIFrequencyMeasurementMethod.LargeRangeTwoCounter, 0.001,
    (long)divisorNumericUpDown.Value, CIFrequencyUnits.Hertz);
    counterTask.Timing.ConfigureImplicit(SampleQuantityMode.ContinuousSamples, 1000);
    // Setup the Counter Input Frequency Terminal to be the Start Trigger from the AI Task
    counterTask.CIChannels.All.FrequencyTerminal = aiTask.Triggers.StartTrigger.Terminal.ToString() ;
    Here's the Error
    Error 1 'NationalInstruments.DAQmx.StartTrigger' does not contain a definition for 'Terminal' and no extension method 'Terminal' accepting a first argument of type 'NationalInstruments.DAQmx.StartTrigger' could be found (are you missing a using directive or an assembly reference?) 
    I'm using Visual Studio 2008, Measurement Studio 2008 Ver 8.5, DAQmx 9.5.5 and NET 3.5.
    Am I missing something?
    Thanks
    Curt

    Hi Curt
    Do you have the proper references included in your project? I am able to run this code as it is with no errors. You should see NationalInstruments.DAQmx under the references of your project.
    This reference is in this path. 
    C:\Program Files (x86)\National Instruments\MeasurementStudioVS2010\DotNET\Assemblies\Current\NationalInstruments.DAQmx.dll
    regards 
    Chris S.
    Attachments:
    Screenshot_1.jpg ‏26 KB

  • How do you measure frequency using the onboard counter on PCMCIA 6024-E

    I am using LABView 6.1 and NI-DAQ 7.2 with a SCXI-1000 chassis and a PCMCIA 6024-E on a laptop. I need to measure a frequency of about 3KHz and would like to do that using an 1180 direct through connector.
    Firstly, should I see this 1180 in MAX like any other module?
    And secondly, how do I use this 6024-E card to measure frequency? Which pins are supposed to be used on it to measure, and will I see the counter run in the test window in MAX according to the frequency measured?
    I know NI also have a frequency module for the SCXI chassis. So lastly, will it be better to use that, rather than measure directly off the 6024-E?
    Any help, advise or comments will be greatly appreciated!
    Thanks!

    Hello,
    I think I can help out with some of your questions. First, the 1180 module won�t show up in MAX since it is really just a feedthrough cable which allows you access to your unused signals from the DAQ card.
    You definitely can measure frequency using your 6024E. An example installs with NI-DAQ 7.2 which shows how to accomplish this. To access this example go to the LabVIEW start up screen and hit the Find Example button. When the Example Finder opens up browse to the following location: Hardware Input and Output -> DAQ -> Counters -> DAQ-STC -> Measure Frequency (DAQ-STC).vi
    This example measures frequency and has a connection diagram on the front panel. The documentation for the example can be accessed by going to File -> VI properties -> Document
    ation, after you have opened the VI.
    You are correct that we offer a frequency input module for SCXI (SCXI-1126). This module would be useful if your input voltages are non-TTL, or if you need to measure more than one channel of frequency signals. This module has an input range of +/- 250Vrms and 8 input channels.
    I hope this helps! Let me know if there is anything I can help with or clarify.
    Ken S.
    Applications Engineering
    National Instruments

  • How to measure frequency with PCI-4474 card

    Hi,
    I'm trying to measure frequency with PCI-4474 card.
    Any sample code available?
    Thanks.

    Hi,
    Thank you for posting the the NI forums.  There aren’t any example programs that ship with the DSA drivers.  Will you be using this with the Sound and Vibration Toolkit?  If so, there are numerous examples that install with this software package.  Check out the LabVIEW Example Finder >> Toolkits and Modules >> Sound and Vibration Toolkit. 
    In addition to this, you could also use the signal processing VIs that ship with LabVIEW.  There are also examples that ship with LabVIEW that use these VI in Example Finder >> Analyzing and Processing Signals FFT and Frequency Analysis.  There is an entire Signal Processing palette that should contain the functionality that you need.
    I hope this helps.  Post back if you have further questions. 
    Ed W.
    Applications Engineer
    National Instruments

  • How to measure frequency when no static line

    Hi. I think to directly measure frequency using DAXmx function my input signal should be connceted to DAQ PFI Lines but in my application the clock frequency is outputted on P0.0 line . Is there any way to directky measure frequency uding DAQmx function or I should do it manually?
    Thanks

    Hi tintin,
    you really should have learned to post good ( read as: meaningful, with sufficient explanations and background information) questions after more than 200 posts in this forum…
    What frequency do you want to measure?
    What is the relation to outputting your own "clock frequency" on some DO pin?
    Which hardware do you use?
    Why do you need to measure a signal frequency when you know that frequency as you output that signal?
    How do you measure frequencies "manually"?
    Best regards,
    GerdW
    CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
    Kudos are welcome

  • How to Measure Frequency to RPM NI-DAQmx Tasks

    Hello,
    I am trying to measure frequency using NI DAQmx task and then convert this to an RPM if at all possible.
    I have the following hardware options at my disposal.
    I have SCXI 1126 Module along with a SCXI 1327 terminal, as well as a PXI 6289 Multifunction DAQ.
    I have wired in a mag sensor to ai7 on my 1126 and when I pass a metallic object I get a amplitude of 6  - 8  so I am able to read the mag sensor.
    What I am trying to do is to somehow convert this analog measurement into a RPM while only utilizing the NI DAQmx task.
    Any help would be appreciated.
    Tim
    Solved!
    Go to Solution.
    Attachments:
    Freq Set Up.jpg ‏2993 KB

    So I would select new in "Custom Scaling"
    Then would I select linear?
    Your calculations are simple but I am unsure if this would give me the desired result.  From my attachment I am seeing an input amplitude of 6 Hz for each pulse.  What I mean by this is that every time I bring a ferrous object near my mag pick up I get a pulse, this is what I was trying to illustrate in the attachment.  The analog pulse comes in a 6 Hz so I would simply multiple this pulse by 60 (assuming I get one pulse per rotation) to get RPM?
    How would this make sense if I only input one pulse for a long duration of time? 
    I have notice the amplitude of the pulse input increases with increased pulse frequency.  Does this mean the lowest RPM I can record is 360 RPM?  
    Tim

  • Unable to measure frequency below 20 Hz on a NIDAQ 9178 chassis with NI 9402 even while using a hardware timed delay

    Hello,
    I am trying to measure frequency using NI 9402 in NI cDAQ9178 chassis. I am setting the clock for my counter channel to be my chassis ai Sample Clock.
    I am able to measure frequency above 20 Hz. For frequencies less than 20Hz, I get the following error:
    DAQmx Error: Multiple Sample Clock pulses were detected within one period of the input signal. Use a Sample Clock rate that is slower than the input signal. Ifyou are using an external Sample Clock, ensure that clock signal is within the jitter and voltage level specifications and without glitches.Task Name: _unnamedTask<0>
    Status Code: -201314
    Setting the Rate to 1 also not does resolve the issue.
    OTHER DETAILS:
    * Running on 64 bit, Win7 platform.
    * NIDAQmx Driver Version: 14.5
    I had posted regarding this earlier and I was told that this might be because the counter is armed immediately before the first sample is taken. The recommendation was to add a hardware-timed delay using the DAQmxSetStartTrigDelay method to the AI task. I have added this delay but I still receive the same error message. The previous post I had mentioned can be found below:
    http://forums.ni.com/t5/Multifunction-DAQ/Cannot-measure-frequency-below-20-Hz-on-a-NIDAQ-9178-chassis/td-p/1537274
    I have also attached my current code which has the delay. Is this a bug in the driver? If yes, can we have a CAR# to track this?
    Thanks.
    Regards,
    Varun Hariharan
    The MathWorks

    Alright so I got everything working correctly in both C and LabVIEW code.
    The problems is in fact with the first sample, as John_P1 suggested. You simply need to delay that first sample from being requested. It is simple to do this in software instead of hardware.
    If you are using CVI, just add #include <utility.h> to the top of your .c file and then add a delay before your DAQmxErrChk (DAQmxStartTask(AItaskHandle)); line.
    Comment out / remove the DAQmxSetStartTrigDelay(AItaskHandle,10); line, as it wasn't doing what we thought it would. (Hardware delay).
    I added Delay (.05); to delay long enough for the full period of the input signal at 20 Hz.
    Depending on your frequency, this value may need to be adjusted. 100ms wouldn't be a bad idea.
    This is expected behavior, and I don't think we need a CAR.
    Let me know what you think!
    -CB

  • How to Measure frequency of less than 300 Hz

    Is it possible to measure frequency without a counter module? All I have is a cDAQ with 9205, 9221 and 9263 modules.

    Hello,
    I am assuming that you want to measure analog frequency, since you have analog input and output hardware.  There is a useful LabView Help file titled Measuring Analog Frequency.  You will be able to measure analog frequency using just software and no counters.  However, this involves using Fast Fourier Transform (FFT) functions that are only available in LabView Full and Professional versions.  Please also take a look at the examples in the Example Finder.  Some helpful ones are titled … Signal Generation and Processing.vi, Spectrum Measurements.vi, and Simple Spectrum Analyzer (sim).vi.  These example’s block diagrams are a little busy, however you can see how they are using simulated signals with the FFT Power Spectrum.vi.  Note that the example titled Spectrum Measurements.vi uses express functions.  These functions are going to involve less programming, but offer lower program efficiency.
    Samantha
    National Instruments
    Applications Engineer

  • Measure Frequency of Digital Signal from DAQ-Board

    I'm using a National Instruments DAQ board and I need to measure the
    frequency of a digital signal from my data acquisition board.
    I know the measure frequency.vi (In diagram - data acquisition -
    counter), but i don´t understand yours implementation mainly in input
    "counter". Because i don't understand the relationship of board channel (for
    signal acquiring ) and the measure frequency.vi.
    Thanks in advance,
    [email protected]

    Hi,
       Attached is a vi which models your signal, and provides a way to measure the average frequency over a window of time. It converts the signal to a sequence of periods. I usually start with this approach because you can save the data in a much more compact form if your sampling rate is high. Obviously over a specified period of time, if there are no zero crossings the frequency is zero, so I was a little incoherent before. The real issue is the latency caused by averaging. Your frequency measurement is most accurate half your window size before the current time, so smaller windows give you more up to date measurements, but also more noisy. If you need the most up to date measurement, then you have to use the time since the last crossing which is the case where the frequency never goes to zero. That's probably not a realistic situation. If you needed less latency, you could use a prediction algorithm.
    Also, there are a number of signal measuring and processing vi's that LV gives you, for instance pulse measurements that could be used to partially implement this or other approaches, but I normally steer clear of them unless they fit exactly due to having to convert back and forth to the waveform data type.
    Have fun!
    Attachments:
    DigRandFreq.png ‏62 KB
    DigitalRandomFreq.vi ‏34 KB

  • Can I measure frequency with a SCXI-1120 module and SCXI-1320 terminal block?

    I am attempting to measure a square wave from a directional encoder to display RPM of a dynamometer. The waveform will have a frequency of 0-4KHz, with 3.6KHz being nominal, at about 5volts RMS. How can I measure the frequency of this waveform with the hardware I am currently using? In addition to what is listed above, I am using a PCI6034E GPIB card and LabView software.

    In order to measure frequency, I would not recommend to use the SCXI-1120, but the SCXI 1126, which is a programmable isolated F-to-V module.
    If by any reason you do not want to use SCXI-1126, then I would suggest to use the counter/timers of your board. The counter/timers are TTL compatible, and are the devices that we mostly recommend for doing precise frequency measurements.
    In order to have access to the counter/timers of your board through your SCXI chassis, you will need SCXI-1180, which is basically a feedtrhough panel for your DAQ board.
    Once we have access to the counter/timers through the SCXI chassis, we can proceed with the coding.
    I found a pretty good webpage that clearly explains how to perform frequency measurement with the DAQ-S
    TC counter/timers (DAQ-STC is the type of counter/timer chip that you DAQ device has). Here is the link to it:
    Pulse Width & Frequency Measurements
    As you will see, this link contains tutorials, application notes and example programs. I would recommend to pay special attention to the example program called: DAQ-STC: Measuring frequency.
    Good luck with your application!

  • How do i measure frequency?

    lets say theres this signal in volts. if you plot the signal it forms a sine graph. is there any way to use labview to determine the frequency of the signal? i've tried to use the "measure frequency vi" but my device is connected to a virtual channel, and i dont think that VI supports that...

    Hi Polly,
    There are several ways to measure frequency in LabVIEW. You can measure the frequency of a pulse train using DAQ hardware (counters). You can also just take a buffer of data and simply use LabVIEW functions to read the frequency of the buffer. An example function would be Extract Single Tone Information.vi. There are many other functions as well. Hope that helps.
    Ron

  • Pins at a PCI MIO-16E-1 to Measure Frequency(DAQ-STC).vi?

    I want to measure frequency with the
    "Measure Frequency(DAQ-STC).vi".
    Can't find the appropriate connector pins
    in the manual of my PCI MIO-16E-1.
    Can someone confirm or correct me?
    Signal - PFI1/GPCTR1_SOURCE
    SignalGND - PFI9/GPCTR0_GATE
    PFI8/GPCTR0_SOURCE - PFI4/GPCTR1_GATE
    Thanks in advance
    Manfred

    Manfred,
    You can find this information by going to the http://www.ni.com/manuals site and viewing the E-series manual. There is a table which shows the pin number, name, and function for each pin.
    Pin 10 - PFI1/Trig2
    Pin 11 - PFI0/Trig1
    Pin 43 - PFI2/Convert
    Pin 42 - PFI3/GPCTR1_Source
    Pin 41 - PFI4/GPCTR1_Gate
    Pin 40 - GPCTR1_out
    Pin 6 - PFI5/Update
    Pin 5 - PFI6/WFTRIG
    Pin 3 - PFI9/GPCTR0_Gate
    Pin 2 - GPCTR0_Out
    Pin 4,39,35,36 - DGND
    Mark

  • Counter 1 - Measure Frequency & Counter 0 - Generate PWM POSSIBLE?

    Is this POSSIBLE with a NI-6025E DAQ card? Can I use the two counters to generate % control a TTL PWM signal and at the same time measure frequency from a circuit? This is my connection.
    GPCTR1_SOURCE - connected to find frequency circuit
    GPCTR1_OUT - connected to GPCTR0_GATE
    GPCTR1-GATE - not in use
    GPCTR0_SOURCE - not in use
    GPCTR0_OUT - connected to DC motor circuit
    GPCTR0-GATE - connected to GPCTR1_OUT
    My concern is that changing or controlling the TTL PWM might change the frequency reading. This is because COUNTER O is connected to COUNTER 1.

    I understand to measure frequency of a signal there are TWO methods. A ONE counter method and a TWO counter method. I need to measure a frequency between 1 Hz to 200 Hz. Is the ONE counter method possible? What is the ONE counter method?

  • How to measure frequencies of two sources simultaneously using 6602?

    I am using pci-6602 & LabView to measure frequencies of two sources. I wired Measure Frequency (NI-TIO).vi to do it, but it seems the counter only works at one channel at a time. Can anybody send me an example vi?
    Many thanks in advance
    ZYuan

    Hi ZYuan,
    To measure the frequencies simultaneously, you would need to duplicate the code for the single counter example twice and link the error cluster from one set to the next. I don't have a specific example but the following example can be used as a guide.
    Simultaneous Buffered-Event Counting on All Eight Counters of the 6602 or 6608 Devices
    http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3DC9F56A4E034080020E74861&p_node=DZ52325&p_source=External
    Hope that helps. Have a good day.
    Ron

  • Measure frequency by singalExpress V2.0

    I am trying to use 6602 to measure frequency   (  2 Counters mode), but i get an error
    "Sample period too Short" even i increase the Measurement Time....
    Attached the Screen Capture, could anyone help me?
    Attachments:
    freq_measure.JPG ‏232 KB

    Dear all, i try to set using 2 counter to measure single point frequency...but why the program SE warm me that the " Sample period too short" , How can i solve this problems??
    Attachments:
    freq_measure.JPG ‏232 KB

Maybe you are looking for