Filtering counter input?

Hello
I've got some RF and scattered interference causing some errant readings from three sensors (two magnetic and one magnetic proximity) which are giving me RPM readings from a spinning shaft.
Efforts to pinpoint and eradicate the interference have been fruitless and I believe I may be stuck with it. It is causing errant high readings.
Here is my subVI for obtaining speed data from a sensor; This sensor is picking up one pulse per revolution on a 12000RPM shaft, 200hz. What I would like to do is be able to filter my frequency input so that the unreasonably high numbers are discarded and not calculated for my mean RPM output.
I found the examples on property nodes and worked it into the flow of my subVI, but I'm not sure how to set it or even if it's going to do what I want it to. I know I can't use a standard 'filter' DAQ assistant since I'm not getting a waveform, but a number. I need desperately to remove these errant high readings from my setup ASAP and cannot afford to waste more time on chasing RF around the room.
I've also been successful at getting RPM data via period, and could use that and apply a filter if someone had an idea.
Any help is greatly appreciated. I am going to also ask in the DAQ forum since this is a hardware specific issue as well.
Still confused after 8 years.
Attachments:
rpmsub6.vi ‏39 KB

Hello Ralph,
Please keep each question to one thread. It helps our community find answers to
questions easier. Thanks for your
support.
The answer to this question can be found here.
Respectfully,
Rob F
Test Engineer
Condition Measurements
National Instruments

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Highpass filtering for counter input signal

Hello,
I need to use high pass filter for my counter input pulsewidth measurement.
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I want to do same thing online.
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I am using pci 6220 for counter input for pulsewidth measurement.
Thanks
Nisarg Shah

Hi Nisarg,
This response is pretty late but have you seen any of the Filter VIs in LabVIEW? Can you apply a filter to your signal with these?
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FP-CTR-500 don't read external count inputs

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There are several reasons that you may be having problems with the count. First, if the channel LED is always on, then the signal wired into the FP-CTR-500 may not be going low enough (below 6 volts) for the module to see the falling and rising edges. Second, if the inputs have been configured with the 200 Hz low pass filter setting, you may be filtering out your signal. Third, if you have configured the count channels for internal count inputs (1 kHz Reference or 32 kHz Reference) or previous count channel, then the module is not looking at your actual wired signals. Fourth, If you have enabled the Gate Inputs (channels 8-11) for any of the counters, then the count will not increment while the gate is low. Fifth, if the channel is configured for Reset On Read fu
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Route multiple 6602 counter inputs to one counter output...

Hi!
I´d like to route 4 different ttl signals, that are read by 4 different counter inputs to one single output channel (e.g. the output of one of the counters used) using pulse train generation with a divider of 4. Note that only one of the four inputs is active at the same time, to prevent overlay.
How can I do that with Traditional-DAQ?
Setup would look like this on the SCB-68
TTL1 ----o in0 (ct0)----o out0 TTL(1..4)/4 [Hz]
|
TTL2 ----o in1 -- (output of ct2 is redirected ro ct1)
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TTL3 ----o in2 --
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TTL4 ----o in3 (ct3)--
May it be better to just output each counter input signal at it´s own output and connect these outputs to one free I/O-pin hardwired?
Best regards
Zorniki

In the end I configured a counter for Pulse Train generation and opted to change the duty cycle and frequency via 'DAQmxWriteCtrFreqScalar" (i.e. Pulse Width Modulation)
I registered a callback for the 'DAQmx_Val_CounterOutputEvent' and then changed the dutycycle and frequency in that callback.
Unfortunately, I kept getting "The pulse generation with previous property settings must complete a
full cycle before the property can be updated." error messages and, opon further reading, managed to find a doc where National Instruments suggest adding a 'Wait(period)' before executing the 'DAQmxWriteCtrFreqScalar' call.
The problem with this solution is that it one has to wait a minimum of 2 Periods before the Pulse Train can be modified which is not acceptable for our work.
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Cheers, Shaun.

Counter input problem

hi, i'm using a counter input to count the falling edges of a digital pulse. I need to convert this into a time based measurement (period/frequency), but am having a litle trouble doing this. If any one can help? i'd prefer it if it were as simple as possible, i.e. no fancy programming as I'm new to LabVIEW and would like to fully understand what i'm looking at!
Many thanks in advance!
tom

Hi
What version of LabVIEW are you using? If you're programming with version 7.0 or higher you can configure your counter for period or frequency measurements quite easily using the DAQ Assistant.
Just drop down the DAQ Assistant Express VI. The Wizard that opens will ask you to choose your input type. Choose Counter Input and it list options for Edge Counting, Frequency and Period Measurement. Choose the one you want then choose the counter with which to do the measurement. When you click Finish a configuration dialog box will open up for you to configure the Input Range, the Task Timing, etc. There will also be some further information in the help section along the right of the window. When you click OK the DAQ Assistant will build your code.
I've attached a Zip file with 2 labview programs to demonstrate this. (They're written in version 8). Connect DIO 0 to PFI 9 of your DAQ card (I'm using an M Series card. If you're using a different card let me know). Extract and run both files. The Digital Output VI generates an alternating high and low signal for each iteration of the loop. The Counter Frequency Measurement VI measures the frequency of this output. The frequency is determined my the Wait Until Next ms Multiple function so change the input to that to vary the frequency.
Let me know how you get on with that and if you require more info.
Good luck!
SarahB
NI | UK
Sarah
Applications Engineer | National Instruments | UK & Ireland
Attachments:
Frequency Measurements.zip ‏65 KB

Counter Output/Counter Input PXI Signals Behaving Erratically

Question for all your LabVIEW guru's out there,
I am running a frequency loopback test using the NI PXI 6229 MIO DAQ card. I am generating a "Counter Output" pulse train signal which feeds through my device under test and then back out of my device under test and back into the PXI 6229 for a "Counter Input" frequency measurement. Both the "Counter Output" and the "Counter Input" are assigned different PFI lines using DAQmx in LabVIEW.
I have 4 lines to test on my DUT. All four lines run this same frequency measurement but with different PFI lines on the PXI 6229. Each line is test independently.
This is my setup for the 4 lines:
Path 1: P2.0 (Counter Output - Pulse Train) -> DUT (Device Under Test) -> P2.1 (Counter Input - Frequency Measurement)
Path 2: P2.2 (Counter Output - Pulse Train) -> DUT (Device Under Test) -> P2.3 (Counter Input - Frequency Measurement)
Path 3: P2.4 (Counter Output - Pulse Train) -> DUT (Device Under Test) -> P2.5 (Counter Input - Frequency Measurement)
Path 4: P2.6 (Counter Output - Pulse Train) -> DUT (Device Under Test) -> P2.7 (Counter Input - Frequency Measurement)
where:
P2.0 = PFI8
P2.1 = PFI9
P2.2 = PFI10
P2.3 = PFI11
P2.4 = PFI12
P2.5 = PFI13
P2.6 = PFI14
P2.7 = PFI15
I have a LabVIEW VI which generates the "Counter Output" and reads the "Counter Input" frequency. I am seeing weird behavior from the PXI 6229 card. I can test "Path 1" and "Path 2" and the frequency I read is what I generated. No issue there. However, when I test "Path 3" and "Path 4" the frequency measurement is erratic. The readings are two different frequencies repeated over and over again and none of those frequencies are the expected frequency which was generated out of the "Counter Output." If I reset the card, and start by testing "Path 3" and "Path 4" the frequency readings are correct and the erratic behavior is gone. However, when I try to then test "Path 2" and "Path 1" now those lines have the erratic frequency issue. I can continue resetting the card and see same issue. The PFI lines that I test first will always pass.
To summarize:
Steps Taken:
1. Test Path 1 = SUCCESS
2. Test Path 2 = SUCCESS
3. Test Path 3 = Erratic Frequency (Two Frequencies repeated over and over again in my frequency results array)
4. Test Path 4 = Erratic Frequency (Two Frequencies repeated over and over again in my frequency results array)
5. Reset the PXI 6229 Card
6. Test Path 3 = SUCCESS
7. Test Path 4 = SUCCESS
8. Test Path 3 = Erratic Frequency (Two Frequencies repeated over and over again in my frequency results array)
9. Test Path 4 = Erratic Frequency (Two Frequencies repeated over and over again in my frequency results array)
I am wondering if Port 2 (P2.0-P2.7) on the 6229 card has certain dependecies and this is why I am seeing issues. I am trying to get around this issue so that I don't have to always reset the card.
Are P2.0-P2.3 (PFI8-PFI11) and P2.4-P2.7 (PFI12-PFI15) treated differently or require different setup? How do I resolve this issue?
Thanks so much!

I have a theory...
The DAQ card follows a policy called "lazy uncommit" wherein the terminal used for the output will continue to be connected to the counter even after the task has completed (until the terminal is needed for something else). So as you run more tests, the counter output will end up driving more lines. This behavior should be easy enough to confirm.
As the DAQ card drives more lines, I'd imagine this affects the actual signal. You could scope it to check, but it sounds like either the rise/fall times are becoming longer or some extra noise is being introduced on the line.
The readings are two different frequencies repeated over and over again and none of those frequencies are the expected frequency which was generated out of the "Counter Output."
This implies you are picking up an extra edge during transitions--this isn't too uncommon if the signal is noisy since there is no built-in hysteresis on the DAQ card. I would expect the measured frequencies to have periods that sum to either the full period or the semi-period of your actual signal (depending on how many duplicate edges are detected).
Suggestions are as follows:
To stop the DAQ card from driving multiple PFI lines, it would probably be easiest to just programmatically reset the device in between your tests (using DAQmx Reset Device). If you can't reset the device (e.g. because you are running some other task that can't be interrupted) then you can instead configure a dummy task that uses the PFI line in question as an input.
To stop the DAQ card from picking up multiple edges during transitions, you should configure a digital filter on the input terminals. If you reset the device it sounds like this might not be necessary... it's up to you if you want to configure this or not.
Best Regards,
John Passiak

Custom scale for counter input?

Hello everyone,
Is it possible to create a custom scale for a counter input? I saw there is a feature to allow input Custom Scale Name to the Channel Property Node. However, when I tried to create a custom scale to input to the channel, I got this error
Error -200212 occurred at DAQmx Read (Counter DBL 1Chan 1Samp).vi:1
Property: CI.MeasType
Corresponding Value: Count Edges
Property: CI.AngEncoder.Units
Corresponding Value: From Custom Scale
Channel Name: CountEdges
Task Name: MyCountEdgesTask
Do you know what is the problem with it? Thank you

How do you have the channel set up? Can you attache the VI's that you are using? Is this a global virtual channel?
Tim
Johnson Controls
Holland Michigan

6251 Counter input signal

Hello,
I am acquiring pulses which are 0-5V with the counter of the PXI 6251. However, I would like to know if it is possible to acquire pulses that are, for example 0-12V or 0-24V without damage the device. In other words, which is the voltage range for the counter input in a PXI 6251?
thanking in advance,
CJMV

Hi,
You will not be able to use the counter directly but you can setup an analog level trigger for your signals. This will create a pulse that isTTL compatible for you everytime the signal crosses a particular level. Then you can route this into your counter and perform any counter measurements on it. An example is this is shown here where it sets up a level trigger to make frequency measurements.
Alternatively you can purchase an industrial strength digital I/O board such as the USB-6525 but this does not include a counter.
Please let me know if this works out for you.
Message Edited by Abhinav T on 07-06-2007 05:20 AM
Abhinav T.
Applications Engineering
National Instruments India
LabVIEW Introduction Course - Six Hours
Getting Started with NI-DAQmx
Measurement Fundamentals

Encoder position WITHOUT counter input

Question:
I have three incremental encoders connected to my M-Series DAQ board (PCI-6229) that has TWO Counter input channels. I am measuring the position of each encoder. How do I measure the position of the third encoder if I have used-up both counter inputs? Is there a manual way to accomplish this using my older version of Labview (version 7 express)? Any help is appreciated.
-Clarkam1

clarkam1 wrote:
Ben,
I'm on an extremely small budget and can only use the items available to me at present time. That being said, is there no way to use one counter for multiple encoders? Or could an external device be used to count which the DAQ board would read? I appreciate your timely responses. I'm trying to explore all other options.
So do you work for free?
If you are determined to get all three counters going with that device, you have a big challenge ahead of you. I'll try to explain. At teh input of your counters you have signal conditioning that feeds the counter itself. To do the same thing using analog input channels (since all of the counters are already used) you will have to develop code that simulates the signal conditioning, converts the analog to digital (this may sound easy but if you need to implement over-sampling its not) and then do the work of the counter, again in software.
If my customer was forcing this on me I would first review the behavour of the hardware and use it to establish the requirements of my code. So if you do not have an EE background, you will first have to learn the hardware so you can write software that does the same thing.
So if you work for free then you may want to chase down the examples that NI ships for their FPGA targets that implement serial protocols and the like. You may be able to harvest some code and examples from there. If you don't work for free, then you really have to decide if you want to re-invent in software what you can purchase.
Ben
Ben Rayner
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Benchmarks for Buffered Counter Input with X-Series Devices

Hi,
Does anyone know the maximum transfer rate (using dma) for the x-series cards?
I'm looking for data simillar to the one in this link:
http://digital.ni.com/public.nsf/allkb/72A7E41EE5A8756A862571DA0076F1D7?OpenDocument
More specifically I want to know the transfer rate for the PCIe 6343.
Thank you,
Eyal
Solved!
Go to Solution.

I benchmarked 8MS/s on a single channel on a USB-6353 (should have similar performance to the USB-6356/66) with a buffered counter input task. This was only a 10 minute test on my Dell E6400 laptop ( Windows 7 32 bit, Dual core P8600, 4GB memory) so a sustained 24/7 rate is likely less. Also, I wasn't doing much with the data, just displaying it in an array. This is pretty much topping out USB streaming on this system (32MB/s) so I wouldn't expect to get higher. I wasn't running much else in the back ground (Explorer, Powerpoint, Lotus Notes) and CPU was at ~20%.
Hope this helps,
Andrew S
Getting Started with NI-DAQmx
Measurement Fundamentals

Low Pass Filter Counter Input Compact DAQ

Hello,
I need to put a 10kHz Low pass filter on a counter input.
I have a CDAQ 9178
and a 9421 Digital Input module
Acording to the documentation and my own experience I can't enable the filter on the Digital input card.
Is there another way to do this? I need to filter the signal in hardware.
Thanks
Dan

Your filter might work, however it is build to filter power lines, with current rating 6A and powerline voltage. You pay a lot for a box with screw terminals and a lot of copper and high rated capacitors.
Have you tried a simple RC lowpass (costs less than 50 cent, even when purchased in a pharmacy ) ? R=1500Ohm, C=10nF gives a coarse 10kHz first order lowpass. The C fits between the ground and input terminals of your DAQ, the R in the signal line to the input.
Output impedance of your source?
If you explain more of your application, type of signal, we might find other solutions.
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

Graphing Encoder Counter Input in LabVIEW Signal Express

In LabVIEW SignalExpress, using a simulated daq system with a counter input, I set up a DAQmx Acquire of an Angular measurement based on a quadrature encoder. Acquiring N samples, I acquired a table of measured values. I would like to plot the results, however, I am not given the option to view the data in any other format. I can plot if I acquire one sample, but that does not allow me to sync the data with the analog input signal I would also like to acquire and view. I had to use an external clock to take the encoder data, so the data is acquired a double datatype. I would like to be able to view in realtime, encoder position with respect to time.

HI,
I want to obtain of this combination of hardware and software a system that allow me acquire a signal of the load cell and the counts of the incremental encoder’s pulses and represent in a graphic the force vs the distance.
The distance is pick up to a incremental encoder in a worm gear that with its movement, move a load cell in a base. the reading of the position is in millimeters.
In this moment, I can only represent the force, the position is only visible in a display, I want to take a samples of the force and the count in millimeters, ten or more times per second and perform a graphic in a real time.
Thank you for your answer
Best regards
Lizardo Laguna

Save counter input data against time

Hello, i would like to know about recording using a write to measurement file.
When i record a data like analog input, at the save file with display the analog data against time.
But when i tried to applied for the encoder, which is using counter input, in the .txt file dont display
the result as analog input. So can someone give me a guide on what to setting on write to measument
file to measure the revolution per minute rotation against time, thanks
Solved!
Go to Solution.
Attachments:
encoder recording.vi ‏180 KB

There is no setting for the Write Measurement File. Your problem is that you are passing a scalar to the function and that scalar has no timestamp information. When you use an analog acquisition, the data type is either a waveform or dynamic data type. Below is one way to add the timestamp information. You also should have a delay or msec wait in your loop. This can be used for the dt information.
Message Edited by Dennis Knutson on 09-24-2007 09:51 AM
Attachments:
Save Scalar with Timestamp.PNG ‏6 KB

Vbnet counter input channel read

VB2005 Counter Input DAQmx Single Reading
I have been tasked with upgrading a previous vb6 application using DAQ Legacy
to .net using pre-existing components.
6052E and 6601. I am a vb.net programmer, not an engineer,
nor did I write the original application.
- lots of deciphering and figuring out terms that I am very
unfamiliar with.
6052e = Dev1
6601 = Dev2
Encodertype = x4
zIndexEnable = false
EncoderPhase = AHighBHigh
PulsesPerRev = 60
SampleClockSource = “/Dev2/PFI39”
Rate = 1000
Samples = 25
Taken pretty much straight from the example -
myTask.CIChannels.CreateAngularEncoderChannel(counterComboBox.Text,
encoderType, zIndexEnable, zIndexValue, encoderPhase, pulsePerRev, _
0.0, CIAngularEncoderUnits.Ticks)
myTask.Timing.ConfigureSampleClock(sampleClkSourceTextBox.Text, _
Convert.ToDouble(rateTextBox.Text), SampleClockActiveEdge.Rising, _
SampleQuantityMode.ContinuousSamples, 25)
I have installed DAQmx 8.5 and have been reading the help
and scanning the samples to try and figure these things out.
Specifically MeasAngularPositionBufferedCont_ExtClk, after calling
and getting help, I was finally able to get this sample to work.
In my application, I have my own counter object that I
instantiate and each of the four has its own task, CIChannel and reader. When a
channel is selected, the task is configured, the channel added, the task timing
configured and the task started, when the object is unselected, I dispose of
the task and channel. In my gui I have a timer event and if that channel has
been selected, then I call its getcurrentvalue method, which calls the reader
to get value asynchronously and pumps it to a textbox. This same type of scheme
worked for me with the AIChannels, but trying to get counter angular position,
all I am able to get is error -200284 pretty consistently.
I have matched all my criteria to the working sample, but am
unable to get a value returned. Better yet, after I start my app, even if I don’t
enable one of my channel objects, I can no longer run the sample application.
I have found that after I run my application I can use the
original application (which is using the DAQ Legacy) and initiate a read and
then close the original application and everything is reset aka I can
successfully run the sample application again.
QUESTIONS:
Is there a way to test the start trigger to determine that it
is configured correctly?
I have the task set up for external timing and the clock
works on the sample how can I verify this is working in code?
Any idea of why I would have to go into the original
application in order to get the sample to work again?
Any know of other vb code examples that might relate that
you could point me to?
Thanks for any help
CMWell, time to get back to the frustration...

Hi,
Is there a way to test the start trigger to determine that it is configured correctly? - Where are you using a start trigger? - I didn't see a mention of it in your description. When troubleshooting triggers I ussually end up checking 3 things. First, I confirm that my physical trigger source is outputting a TTL signal. Second, in Max I do count events on the PFI line I have the signal connected to in order to confirm my connections. Third, I try a simple example - if it will trigger in the example, then it will trigger in my code as long as the call is made with the same settings and configurations.
I have the task set up for external timing and the clock works on the sample how can I verify this is working in code? I would start with the first two steps from above. In your case, PFI39 is an actual enoder signal if I recall correctly. With the error that you receive, -200284, one of the causes of that is when there is not external clock signal (do a quick search on ni.com for "200284" and check out the first link) - is your encoder moving when you take these readings? If there is no clock signal present, then the task will not latch in values. One good way to work around this is to use another one of your counters to generate a pulse train and use that output as a clock signal instead of PFI 39. Also, if you just want to grab single values, you don't have to do a buffered acquisition - you can figure timing for "on demand" and not have to woory about clocked values. Either method should work.
Any idea of why I would have to go into the original application in order to get the sample to work again? That ones a little tougher. If somehow you are leaving the task in an undefined state (not stopping and clearing) it can cause some issues with the next iteration. You may want to try reseting the device at the beginning of your program.
Any know of other vb code examples that might relate that you could point me to? I think you're already looking at a good shipping example, you may want to try modifying that before trying different setups in your application.
Hope this helps, please don't hesitate to post back to this thread with additional questions,
Andrew S
National Instruments
Getting Started with NI-DAQmx
Measurement Fundamentals

How to convert the counter input as a RPM

Hello NI,
Could you tell me. how to convert the Counter input to the RPM. I am using Rotary encoder has a 5V amplitude with 500 PPR. i am going to measure the Engine speed as a rpm.
I am using third party hardware, from the hardware i can get the Count as well as Frequency also.
Could you suggest to me...? i looked out some disscussion in these forum but i cant able to understand.
can you please explain with simple way....
if you have any simulation send me....
Regards,
Balaji DP

Hi balaji,
[email protected] wrote:
...I am using third party hardware, from the hardware i can get the Count as well as Frequency also.
If you're able to read frequency as X pulses/sec(?) that seems to convert RPM as follows:
X (pulse/sec) * 1/500 (rev/pulse) * 60 (sec/min) = X * 60/500 RPM (???)
Cheers!
"Inside every large program is a small program struggling to get out." (attributed to Tony Hoare)

Filtering counter input?

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