No reading on the frequency counter

I'm not getting a reading on the frequency counter when I wired the clock signal onto it. There's just one input to the counter, so I wired a clock and try to get a reading. All I see are the dashes. Is there something else I need to do? thank you.

Hi,
You can configure some parameters in the pop-up window of the instrument. Trigger Level, sensitivity and AC or DC Coupling. You can try to set these based on your circuit.
If you want us to take a look at it, please post the circuit.
As an alternate, you can also see the freq in the measurement probe. Go to Simulate -> Instruments -> Measurement Probe and click on the net (wire) where you want to check the frequency.
Hope this helps.
Regards,
Tayyab R,
National Instruments.

Similar Messages

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)

What's the maximum counter frequency for the cRIO?

Hi Everyone,
First of all, thanks for your input here!
I'm new to the cRIO, but have been working with LabVIEW for awhile. I need to accurately measure the time between several digital inputs. One input starts the counter, another captures and stores the current counter value, and a third stops the timer and also captures and stores the counter value. It's basically a stopwatch. The problem is that the counter needs to run at a frequency of 100Mhz or greater. It also needs to be at least 28 bits wide so that it won't overflow between start and stop inputs. Is this possible with any of the cRIO systems currently available? If so, how? I'm assuming it will need to be implemented within the FPGA, but does the FPGA run that fast?
Thanks so much!
-Yohan
Solved!
Go to Solution.

Hi Yohan,
Unfortunately, the cRIO is not capable of reliable frequencies at 100 MHz or greater. I would recommend speaking with your local NI Field Sales Engineer or callteh NI Sales department at (888) 280-7645 to discuss the hardware that would accomodate your application.
The PXI-6586Rmay be an option: http://sine.ni.com/nips/cds/view/p/lang/en/nid/207297
I hope this helps!
Kristen H.

Using the 6525 counter to measure frequency: is there a neater way?

I'm currently using the high speed counter on the a USB 6525 module to measure the frequency of a spinning object via a hall effect sensor.
I was wondering if there was a simpler/ more effective way of coding it than this?
Currently all I do is take the current counter reading, wait a second, take another reading and subtract one from the other. The result is the frequency, in hertz.
Is there a way of getting the 6525 to return the count/ change in count after 1 second?
Thanks
Solved!
Go to Solution.
Attachments:
6525 frequency count LV8.vi ‏25 KB
6525 frequency count LV2013.vi ‏15 KB

Thanks for commenting. I'm not sure if I'm doing it right though or whether the NI USB 6525 can't handle this type of measurement?
I keep on getting an error that says to effect it can't do this type of operation.
Can you advise?
Thanks
Attachments:
6525 frequency count LV9.vi ‏36 KB

How to measure the frequency of a pulse being generated by a counter

Hi,
I am using labview 8.6 to generate 5 evenly spaced pulses for every 1 revolution of my shaft. However, I would also want to know the frequency of these pulses so I can determine the shaft speed. Since I am already generating the pulses using one of my counters, can I still tap into that or task another counter to measure the pulse frequency? If so, how? I have attached my code for generating the pulses and I am using an Ni 9401 module and an NI 9172 chassis. If someone can helo me modify the code to measure and tell me the pulse frequency as well, that would be really appreciated
Attachments:
autotrain2.vi ‏19 KB

You'd probably get a more coherent answer if you didn't bounce around from thread to thread so much...
How can I generate a pulse train from shaft encoder? (5/13)
pulse train from encoder (5/15)
how to measure rpm (5/20)
How to measure rpm using shaft encoder and labview (5/23)
This thread (also 5/23)
I see you ignored my suggestion from the other thread--Kevin's solution is good too but using an encoder task offers more noise immunity (I think this is probably the cause of the problem you reported on the other thread). You can fix it with digital filtering if you want to keep using a counter output instead of an encoder task. Noise during transitions is pretty common for a quadrature encoder.
A finite counter output task uses 2 counters on the 9172 (although you said 9174 earlier at one point--this wouldn't be the case on a 9174) so you wouldn't have one left to make your frequency measurement. With the solution you have now, you can change to continuous to free up a counter if you don't care about outputing an exact number of rotation's worth of pulses (I'm not sure if you do or not--I didn't read through all of the various threads relating to this application to find out).
For your actual question in this thread... Have you tried running one of the frequency measurement examples? From the code here I can't tell what you have tried (it just looks like a mangled version of the code Kevin gave to you in your other thread).
Best Regards,
John Passiak

Accuracy of the frequency reading - too 'noisy' reading

Hi,
I am measuring frequency of revolution = rpm of a camshaft.
I am using method 1 and method 3
My card is 6221 with 80Mhz timebase.
The TTL pulses come from IRC mounted on the camshaft.
If I switch the IRC to 3600 pulse per revolution I would expect the reading error to be at 3000rpm max 7rpm (see calc bellow)
Err=fx*fx/(fk-fx)
fx= FreqCam*ppr=3000/60*3600=180e3Hz
fk=80e6Hz
Err=406Hz=7rpm
So why does my signal has so much of noise? See picture. The amplitude of the noise for method 1 is around 400rpm and for method 3 150rpm. For now I use moving average filter but I want to know what is going wrong.
Thanks
LV 2011, Win7
Attachments:
PicNoise.png ‏51 KB

The width of the pulses coming from the IRC is going to have more variance than the pulses coming from your function generator (the 7 RPM error that you calculated assumes an ideal TTL signal at a perfectly consistent frequency). Variance in the signal itself would explain why method 1 (inverse of a single period) is more "noisy" than method 3 (inverse of the measured time for a specified number of cycles). Method 3 is essentially just averaging multiple consecutive period measurements together before inverting to obtain frequency.
The measurement from the function generator looks pretty good. With an ideal 180 kHz input you should expect just the two possible measured frequencies:
80 MHz / 445 = 179775
80 MHz / 444 = 180180
It looks like an extra pulse of the timebase was counted during one of the periods that we would have expected 445 pulses, giving a measured frequency of of 179372 (80 MHz / 446). The extra pulse may have been counted if it occurred while the input signal was transitioning between .8V and 2.2V. Something like this:
So, I think the noise that you're seeing with the IRC is just the variance in the output of the IRC. The more accurate reading on the function generator confirms that the card is performing adequately.
Best Regards,
John Passiak

How do I use the buffered counting mode at a fixed frequency?

Hi-
   I'm using a PCI-6259 M-series board with the Nidaq MX
drivers in Labview 7. I am trying to use one counter to do
buffered edge counting (eg. count how many pulses appear on one input
in 400 successive time bins of 10 uS each following a digital start
pulse). That is, my inputs are:
     Start Pulse (from experiment)
     Count Pulse (from a photomultiplier tube in the experiment)
And I want to know:
    # of pulses from 0 to 10 uS after the Start Pulse
    # of pulses from 11 to 20 uS after the Start
Pulse (or, equally good, # of pulses from 0 to 20 uS....I can
subtract later)
    # of pulses from 3991 to 4000 uS after the Start Pulse (or, # of pulses from 0 to 4000 uS...same thing)
   The Count Digital Events-Buffered-Finite-Ext Clk.vi sample
appears to do half of this. I can set this up CTR0 with the Count
pulse (and possibly add the start pulse as an Arm Start....I can't use
a Start Trigger, right?). However, I need to generate a Sample
Clock Source at 100 kHz (to trigger the card to buffer the counter
value and start counting in the next bin). So, I tried to set up
CTR1 along the lines of Gen Dig Pulse Train-Finite-Dig Start.vi for
generating a finite pulse train starting on a digital trigger, and
connecting the output from CTR1 to the Sample Clock Source on
CTR0. However, I get an error -50103 saying the specified
resource is reserved if I do both at the same time. But, I can't
see any resource conflicts...the pulse generation on CTR1 works fine
alone, as well as the buffered counting on CTR0, and all the PFI pins
are different. Is there some reason I can't use both counters at
the same time?
I think I can use the FREQOUT pin on the card to generate a Sample
Clock Source at 100 kHz, since I think this is independent of CTR0
& CTR1. However, I can't trigger the FREQOUT to always start
when I get a Start Pulse (as I can if I trigger a Digital Pulse Train
to start on a digital trigger...or can I?)...so my bins will move
randomly by up to 10 uS.
   This is an unrelated topic, but is there a discussion of
the relationship between the terminology in the manuals describing the
cards (SOURCE, GATE, OUTPUT terminals) and the terminology in NidaqMX
(Source Clock/SrcClk.Source, CI.CountEdges.Term, CO.Pulse.Term)?
Eg. is CTR0.GATE always the same thing as SrcClk.Source, or does it
depend on the mode of operation? If the M-series hardware manual
says to connect something to the SOURCE input, how do I assign an
alternate PFI pin to that SOURCE input in Labview? Does it depend
on the counter type, or is it always the same?

Dave,
Hi, you brought up several questions / issues -- let me see if I can help with some of them:
   I can set this up CTR0 with the Count pulse (and possibly add the start pulse as an Arm Start....I can't use a Start Trigger, right?).
Yes, you could set up this way. Also, as far as I know you're also correct that you need to configure for an "Arm Start" trigger using the DAQmx Trigger property node. The "Arm Start" trigger is used for counter input (measurement) apps while the regular "Start Trigger" can be used for counter output (pulse generation) tasks. I don't think I've experimented with recent versions of DAQmx though so it may have changed in 7.4 or 7.5
...I tried to set up CTR1 along the lines of Gen Dig Pulse Train-Finite-Dig Start.vi for generating a finite pulse train starting on a digital trigger, and connecting the output from CTR1 to the Sample Clock Source on CTR0. However, I get an error -50103 saying the specified resource is reserved if I do both at the same time
I highlighted the problem -- the FINITE pulse train. DAQmx uses CTR0 as a "helper" when you generate a finite pulse train on CTR1. It would generate a single pulse whose width corresponds to the exact amount of time needed for CTR1 to generate its specified # of pulses.
For your specific app, I think you could generate a triggered continuous pulse train with CTR1 -- this wouldn't need to use CTR0 as a helper.  The Start Pulse would arm CTR0 at the same instant that CTR1 is started.   If you set up CTR0 to acquire on the trailing edge of CTR1's pulses, then you'll get the time bins you want.
A final slight mod would be to setup CTR0 for measuring buffered periods (set units == "Ticks") instead of counting edges. In that mode, you wouldn't have to do the subtraction at the end.
   This is an unrelated topic, but is there a discussion of the relationship between the terminology in the manuals describing the cards (SOURCE, GATE, OUTPUT terminals) and the terminology in NidaqMX (Source Clock/SrcClk.Source, CI.CountEdges.Term, CO.Pulse.Term)? Eg. is CTR0.GATE always the same thing as SrcClk.Source, or does it depend on the mode of operation?
There's an NI app note and some discussion forum hits if you search the site for "daqmx terminology."
If the M-series hardware manual says to connect something to the SOURCE input, how do I assign an alternate PFI pin to that SOURCE input in Labview? Does it depend on the counter type, or is it always the same?
Usually, that choice would be available under the DAQmx Channel property node.   There'll be some place to define where the input signal is coming from, generally with "Term" or "Terminal" as part of its name.   Sorry I can't be more specific as I'm not at my LV computer now.
Happy counting!
-Kevin P.

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

Measure a frequency out of the trigger counter sample vi

Hello,
I want to measure the frequency of the simulated signal. I already succeeded in counting the pulse when rising. I probably need to integrate a wait until moduleso it will count the rising signal per time unit. I tried this but it didnt work out. Can you help me so that the VI will display the frequency with the wait until module.
Kind regards,
Michiel Huijgen (the Hague university, Holland)
Attachments:
Trigger Counter vb.vi ‏241 KB

Start a game with the correct resolution / refresh rates https://wiki.archlinux.org/index.php/Ga … e_X_server

Unable to read the frequency!

my programe reads in off an lvdt transducer through a labjack my programe works up until the LJ stream graph process reads to "scaled data v's seconds" graph.where it graphs a sin wave (amplitude vs time)
for some reason the "freq. amp." analyser won't read the frequency correctly. when i run the programme it outputs a frequency of zero.
note: the amplitude is reading correctly
Attachments:
problem.vi ‏77 KB

Your actual data are not accessible and the sub-VI is missing. If you could re-post your VI with time data saved as default on your graph that would be helpful.
In the mean time ... few comments:
- You are attempting to display Amplitude vs. Frequency on an XY-graph. However your graph "data" are just two scalars representing respectivelly the single value amplitude and the single value frequency. This will only give you one point on your graph.
- What exactly are you trying to display? A set of multiple amplitudes vs.frequencies? The spectrum of your signal?

Unable to read the frequency from this output sine wave of amplitude VS time

my programe reads through a labjack programe works up until the LJ stream graph process reads to "scaled data v's seconds" graph.where it outputs a sine wave (amplitude vs time)
for some reason the "freq. amp." analyser won't read the frequency correctly. when i run the programme it outputs a frequency of zero.
note: the amplitude is reading correctly
see both programmes attached..................
Attachments:
problem.vi ‏77 KB
LJstream_graph_processing.vi ‏46 KB

I don't really see the utility of this VI, however, the variable "scan rate", of the "LJstream graph processing", it's an arbitrary value, why?...
What is the idea with these VIs?, tell me more, please.
Bye.

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

Full programme posted!! unable to read the frequency

my programe reads in off an lvdt transducer through a labjack my programe works up until the LJ stream graph process reads to "scaled data v's seconds" graph.where it graphs a sin wave (amplitude vs time)
for some reason the "freq. amp." analyser won't read the frequency correctly. when i run the programme it outputs a frequency of zero.
note: the amplitude is reading correctly
At the end i am looking to have a point on the x-y graph. it is the the output needed for my project.
note: everything works upuntil the scaled data V'S seconds graph
Attachments:
fullprogramme.vi ‏450 KB

The subvi that produces the output for the "Scaled Data vs Seconds" is not available from your upload--it appears to be your problem.
I attached a jpeg of a test I ran on the last part of your vi--it should work successfully. The simulated signal correctly produces a point on the X-Y graph for amplitude and frequency which is what you desire I believe. If you can find the problem in "LJstream graph process.vi" the output part should work correctly.
Attachments:
test.jpg ‏42 KB

Reading the frequency of occurences

I want to be able to count the number of times each character occurs in a sentence, and set this number to be the variable FREQ. So if there were 5 e's and 6 x's, then in the "e" object, the FREQ variable would be 5, and in the "x" object the FREQ variable would be 6. Can anyone help me with this?

> I read thru the entire string and I make a new object
for each character. But I dont know how exactly to
check if an object already exists for that character,
and if that does already exists, how to add 1 to its
freq value.
You can use an implementation of a Map:
http://java.sun.com/j2se/1.4.2/docs/api/java/util/Map.html
It let's you store a key-value pair (Map<Character, Integer>).

TS3899 I have an iPhone 5 and it shows on the Mail Icon that I have over 3,000 emails to read but the number continues to increase even when I have read the email. I thought once you have read an email it drops off the count of "new emails"

I have an iPhone 5 and it shows on the Mail Icon that I have over 3,000 emails to read but the number continues to increase even when I have read the email. I thought once you have read an email it drops off the count of "new emails"

The received emails should show in two locations:
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No reading on the frequency counter

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