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

Similar Messages

Highpass filtering for counter input signal

Hello,
I need to use high pass filter for my counter input pulsewidth measurement.
I can do offline filtering on stored pulsewidth signal.
I want to do same thing online.
Is there any way to do it?
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?
If this does not address your question, please provide some more information regarding your application, what you want to achieve and what you've tried.
-Cindy

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)
|
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.
So is there an alternative solution which allows us to change the Pulse Train after only 1 Period ? Is there an event we can trap which allows us alter the Pulse Train after every period ? I'm sure PWM must be possible on Daq cards (PCI-6602 or PCI-6281 or PCI-6259)?
Cheers, Shaun.

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

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

4 counter input & 6 signal input HELP

Hello Friends,
I have a little problem, would be great if someone can help me.
I am using the counter inputs on my Data Acq. Harware to measure the pulse width of my input sigal.
Since the hardware has only 4 counter inputs I can connect 4 channels, but I want to measure pulse width for 6 channels.
Is there a way to use the available 4 counters and measure all of the 6 channels?
Thank you
Regards,
Raj
Solved!
Go to Solution.

In my (very basic) example, you could just increase the timeout to ~10+ seconds to ensure you acquire the pulse. If it's possible that the pulse isn't present within the ~10+ second timeout you would also need to handle the timeout error so it doesn't wrap back around through the shift register and prevent the future reads from executing.
The downside to this of course is that it could take up to ~60+ seconds to acquire from all 6 channels in the worst case scenario. The example was really just intended to show how one might use a single counter to acquire from multiple channels in succession.
The better way to do it with counters would be to run (up to) 4 counter tasks in parallel. The first 2 tasks to finish with their original acquisition should then measure a second channel. This could still take ~20 seconds if none of the signals are connected however.
If you want to trade a lower measurement resolution (and more memory usage) for a lower upper-bound on measurement time you could instead acquire a 10 second window of time using clocked digital inputs and use software to determine the pulse duration by parsing the acquired array.
Best Regards,
John Passiak

Using PXI 6251 counter to delay a trigger on PXI

Hi at all,
I need to synchronize some devices on an PXI chassis. Basic operation is a user waveform generation on a PXI5401 that routes the Trigger Signal for the generation to one of the PXI (RTSI) lines. I'd like to use this trigger signal to start a counter on a PXI 6251 counting the PXI 10MHz Clock. No problem so far ( at least none that I see What I need is a possibilty to set another sync signal as soon as a certain counter value is reached in order to use this signal as a delayed trigger signal. Is it possible? And how? I've taken a look at the LabVIEW Example finder, but haven't found an example yet...
Thanks!
Oli
P.S. Using LabVIEW 7.1.1, NIDAQ7.4 and a PXI 1042 via MXI4
Programming languages don't create bad code, programmers create bad code....

Nathan,
Thanks for your excellent solution. I'm ordering the Aux100 cable (9-Pin DIN to two BNC Female) to export the trigger signal from the PXI to the Device_2. I will test the program (Echo_Mode_PXI_5122.vi) to be sure it will be suitable for my application.
Another problem, when my system is working on ultrasound Pulse-echo mode (Pulse_Echo_Mode_PXI_5122.vi), the input trigger must be set a delayed trigger acquisition (by setting the trigger delay to, for example 3µs) to remove the signal of power source. Could you please tell me how I can configure the digitizer in this case?
Regards,
John C.
Attachments:
Echo_Mode_PXI_5122.vi ‏49 KB
Pulse_Echo_Mode_PXI_5122.vi ‏49 KB

Input signal (pulse from encoder) analysis

Hi everyone,
I am using a rotary encoder to analyze the motion of a rotation shaft that is driving a piston. I want to verify that the piston's motion is consistent cycle-to-cycle and measure the frequency of rotation. My encoder outputs a Z-signal, which will pulse once per rotation, and an A-signal, which will pulse 500 times per rotation at equal distance increments around the axis of rotation.
I have looked at a number of sample VIs that analyze a waveform for dominant frequency, but those generally use a simulated waveform, and I don't know how to get the signal that I am reading into the DAQ into the correct form to analyze it this way. If I use the DAQ Assistant, my data is the blue type and I need Waveform to use the Pulse Measurements VI.
Also, if anyone has any thoughts as to the best way to verify that the rotations are consistent (I was thinking of subtracting different periods to see if the difference falls below some threshold), I would love to hear them.
I am using LabVIEW 8.5 (I know, an older version) with a PCI-6251 DAQ. I have done the 6-hour LabVIEW tutorial so I am somewhat familiar with the program, and have access to a number of VIs written by others in my lab, but they tend to be pretty complicated, and use DAQmx, which seems to require a number of different VIs.
Thanks in advance!
Meghan

unclebump, thanks for those examples. I am trying to use them as a basis for the VI I need.
Will, thanks for the offer for more help - I think I'll take you up on it!
I'm currently working with the quadratureencoderm-series.vi from the examples (the dir_encoder_corr_dig_port.vi looked much more complicated). I changed the DAQmx from Counter Input>>Position>>Angular Encoder to Counter Input>>Frequency. This should work to read the frequency of the Z-signal? (Currently my encoder is broken and I am waiting for a replacement so I can test this out).But just trying to run the vi, I get:
My I/O to the DAQmx has an option of Dev6 (my PCI-6251) ctr0 or ctr1, the only two options even when I hit Browse...so the only options it gives me are unsupported?

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

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:
1) in my block diagram, the DAQ assistant blocks for both sensors are wired to their respective waveform graphs (one for the LVDT signal and one for the force signal), the whole being included in a while loop (which remains true until the motor stops moving). When running the program, only one signal is read out at a time and I have no control on which signal is transmitted (this seems to occur in a random fashion). Do I need to "link"/synchronize the two DAQ assistants in some ways so that both signals will appear simultaneously? If so, how would it be possible?
2) ideally, I'd like to read out both input signals on the same graph (with 2 different y-scales but the same time scale) to observe the phase shift. I tried to "bundle" the two data output coming from the two DAQ assistants but it resulted in an error saying that the two outputs were of different types. Is there a way to plot these two physical quantities on the same graph even though they're different and come from different sensors?
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

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
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

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'

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

PCI-6602 - What to do with unused counter inputs?

I've got an application where I need to track the position on two quadrature encoders. I've developed my application with VB6 however, I've been using a sample LabView program called "Meas-Ang-Pos-Buff.vi" for testing purposes. (I got the example off the NI discussion board). I'm seeing some very odd results that I can't explain.
For testing purposes, I've got one encoder tied to multiple channels on my 6602. I have the same 'A' signal and the same 'B' signal (from the one encoder) jumpered to multiple encoder channels. I'm using a onboard pulse generator to generate the latch pulse (connected to the Index/Z of each counter) to ensure there is no skew in my count values. I'm using an external servo to turn the encoder at a rate equal to my application speed.
The unexplanable results I'm seeing are below:
If I'm monitoring counters 0, 1 and 2, I see the following.
1) If I have counters 0,1,2 and 3 inputs connected to the same 'A' & 'B' from my encoder, the counts on all 4 channels (0,1,2,3) track perfectly.
2) If I disconnect counter 3 and only have counters 0,1, and 2 connected to the encoder, then counter 0 and 2 track perfectly, but counter 1 looses pulses (only when traveling in one direction, the other direction seems to be fine)
3) If I connect counter 3 to ground and have counters 0,1, and 2 connected to the encoder, I get the same result - bad.
4) If I connect EVERY counter input (2,3,4,5,6) to ground and only monitor counters 0 and 1, I still get bad results.
In summary, I ONLY am able to see the same number of counts while monitoring 3 channels IF 7 of the 8 counters are connected together (the 8th being my latch).
This happened to me in the past on a previous setup that did the same thing, but I was able to fix it by moving from counter 1 to counter 4. At that time, I chalked it up to a bad counter 1, but I think there is a bigger issue since it is happening again.
Please any advice would be appreciated.

Thanks for the response. This one has really got me confused and any help is greatly appreciated.
To answer your questions, no I have not modified the sample program and I'm using NI DAQ v8.5.
I've decided to break the problem down to see if I could find a pattern, but no such luck. Here is the testing that I've done.
I'm making the following connections while using the sample program I mentioned earlier:
Counter 0...............PFI_39 (term 02) - Channel_A(0).................PFI_37 (term 40) - Channel_B(0)
Counter 1...............PFI_35 (term 07) - Channel_A(1).................PFI_33 (term 06) - Channel_B(1)
Counter 2...............PFI_31 (term 34) - Channel_A(2).................PFI_29 (term 66) - Channel_B(2)
Counter 3...............PFI_27 (term 31) - Channel_A(3).................PFI_25 (term 63) - Channel_B(3)
Note: I connect the "Z" channel for gating purposes in my VB application, but this isn't required in the LabView sample program since the gating appears to be done internally.
My testing results:
1. If I jumper my one encoder to channels 0,1,2, & 3 at the same time, everything works great. Each channel reports the same number of counts regardless of whether I'm turning the encoder in the positive or negative direction.
2. If I disconnect channel 3 and only have 0,1 & 2 connected, then 0 & 2 track perfectly, but channel 1 looses counts in the negative direction.
3. If I only connect channels 0 & 1, then channel 0 counts perfectly in both the pos and neg direction, but channel 1 looses counts in the negative direction.
4. If I connect any channel by itself (0,1,2 or 3), each one counts perfectly.
5. If I connect channels 0 & 4, everything seems to be fine.
Like I said in my previous e-mail, if this hadn't already happened to me in a previous application, then I would chalk it up to a bad board. If I didn't get good results on each individual channel then I would chalk it up to a bad encoder pulse train. However, it definitely seems to have something to do with connecting multiple counters at the same time in a Motion Encoder Application. I have read the 6602 User Manual backwards and forwards looking for a nugget of explanation, but have found none. There was a section entitled "Counter Input Selections" on page 4-12 (table 4-2) that might offer some explanation, but neither me or my colleagues could understand what was being described. Any help deciphering that would be appreciated.
As of now, I'm going to proceed with my application, using channels 0 &4 (just as I've done in the past), however I don't feel comfortable not having an explanation for the 6602's behavior. Any insight would be greatly appreciated.

Isolated Counter Input onSC2345 with FT01

Hi folks,
newbie question: I need to count frequency, direction and volume from a flowmeter. The device supplies two
channels with square wave signals of 50% duty cycle, an Amplitude of 12-18 V. the two channels are behaving
much like the quadrature encoders of electric drives, i.e. the phases of the signals indicate the direction
of flow. I have a SC 2345 with FT01 modules available for the task which according to my understanding
could do the job, but requires TTL level for the signal. Could somebody provide me with hints on creating a
small circuitry (if possible inside the FT01) which provides optical isolation. I'm thinking of a NPN transistor
driving the input LED of a optocoupler device. However, if somebody has a working circuitry it wouldn't
mean less hassle to me creating and testing my own. TIA for any input.

Hello chefgps, & Buechsenschuetz,
National Instruments has a beta version of a product called the SCC-CTR01 that you may be very interested in reviewing. If you are interested, please contact [email protected] for more details.
The SCC-CTR01 is an isolation signal conditioning module for the TTL general purpose counter timer signals from the MIO device which can be used in a SC-2345 carrier in the counter slots. The maximum I/O signal voltage levels it can handle are 0-48V. The maximum I/O frequencies are 400kHz. The conditioning provided by this module is very similar to the PCI/PXI-6624 isolated counter timer boards. I think that the SCC-CTR01 module will be a good solution for your application without the hassle of designing, constructing, testing, and debugging your own custom isolation and attenuation signal conditioning.
Alternatively if you need a released solution right away then please consider the PCI or PXI-6624.
Please let me know if you are interested.
Have a great day.
Dan Hoar
Digital & Timing Hardware Project Manager
National Instruments

6251 Counter input signal

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