NI 9402 edge counter works, no frequency though

Hi guys,
I've been searching these forums for about 20 hours now but I still can't seem to get this to work.
I have a NI cDAQ-9172 with a NI-9402 digital I/O module hooked up to an 360 count/rev optical encoder. The encoder produces square wave pulses equal to the input voltage. I am attempting to use the encoder as a speed sensor for my final year engineering design project. I can easily get pulse counts from the encoder into LabView (v8.5) using both DAQmx functions or the DAQ assistant. I'm pretty new to LabView but I believe I've done all I can with the program itself to make this work.
The problem I get is whenever I try to get a period or frequency output from the DAQ nothing happens. The data output stays at zero. I know the encoder is working because LabView can count the pulses. It's as if the module doesn't have any sample for time at all.
Note: When useing the "Measurements & Automation Explorer" and setting up a Task for frequency measurement, in the Timing Settings section I only have 3 options: 1 Sample (On Demand), N Samples, and Continuous Samples
Should there maybe be more?

Hi Evan,
The default gate terminals should actually be PFI1 (for ctr0) and PFI2 (for ctr1). However, these are just defaults and can be changed if you're using the DAQmx functions (but not the DAQ Assistant).
You don't actually use sample clock timing for frequency measurements (at least not on the 9172). What you could use is "Implicit Timing", meaning that the signal to be measured (which is connected to the gate) is also what is used to latch the sample in. However, in your case it might make more sense to start out using no timing at all--DAQmx Read will merely ask for data once it is called (if no signal is present it will timeout).
Here's a slightly modified version of your VI that should be a good starting point:
To avoid confusion, you can just specify any PFI line that you want for the Input Terminal (I usually do this with counters anyway). Implicit timing is an option that you can add in (before the task is started) but it didn't seem necessary based on what you have described so far.
Best Regards,
John Passiak
Attachments:
Meas Dig Frequency with Terminal.vi ‏25 KB

Similar Messages

How do I use a counter to measure frequency and multiple analog signals in the same VI?

I have a PCI-6071E, an SC-2345 with multiple modules, and a PXI-8184 (with a PXI-1002 Chassis).
My goal is to monitor pressures, flows, temperatures, and speed in one VI.
I am using Measurement and Automation Explorer version 3.1.1.3004 to manage my channels.
My speed is a PWM signal which I recently rewired through the counter 0 of my board.
I was hoping to configure this to read frequency directly in measurment
and automation, have this scale the value to RPM, and then feed it
directly in to my labView program.
In labView, it will not except this signal though.
I get error -200300 from the DAQmx Start Task.vi
Possible reasons(s):
Invalid timing type for this channel.
Property: SampTimingType
You Have Requested: Sample Clock
You Can Select: Implicit, On Demand
After doing some research, it seems that the counter wants "Implicit"
selected for the DAQmx Start Task.vi, but then I cannot use my other
channels. Also, counter is included in the "Sample Clock" option
description, so I do not understand why it is not working.
Does anyone know how to work around this problem or a way to configure the counter so that it will work in this way?
All my other channels are Analog.
Thank you.

I am working on getting just the counter working by using
the program posted previously, and I am running into issues. Periodically I get
the error:
Error -200141
occurred at DAQmx Read (Counter DBL 1Chan 1Samp).vi
Possible reason(s):
Data was overwritten
before it could be read by the system.
If Data Transfer
Mechanism is Interrupts, try using DMA. Otherwise, divide the input signal
before taking the measurement.
It seems to work better if I use cascaded counters, but I need timer 0 for
analog channels when I run this code along with the program for the other
measurements.
I have tried averaging, and selecting different values for the millisecond
timer, and these did not seem to have an effect.
I tried different DAQms configurations and "Counter DBL 1Samp" seemed
to work the best.
The program will work for a while and then it will give me the above error
message.
If I use counter 0 as a cascaded counter input, the program runs fine. If I run
this with other analog channels, it errors out because the analog channels use
counter 0.
If I use counter 1 as a cascaded counter input, it seems to work better than a
single channel, but it will still error out with the above error.
If I use only counter 1, I get the error above even faster.
Also, none of the
configurations give measurements outside the While Loop.
The only place I can add a speed dial for the front panel is within the While
Loop.
Is there someway to get the signal to continuously send out of the while loop?
I thought if I could get the signal out of the while loop, I could condition it
anyway I wanted without the program erroring out.
Any suggestions would be much appreciated.
Thank you.
Attachments:
Counter_error.jpg ‏45 KB

Edge counting inaccurate

I'm getting inaccurate results from my USB-6210 edge counting check from MAX. I have a TTL source that generates four pulses that is connect to PFI0 through a simple RC filter (390 ohm and 0.02uF). I start the edge counting from the test panel in MAX choosing PFI0 as the edge source. When I trigger my four pulses I receive a much larger count (sometime up to 20 counts) from the MAX test panel. Only when I remove the RC filter do I receive an accurate count (4 pulses exactly). I need to use the RC to filter out some 45KHz noise generated by another piece of equipment in the lab. I know I can set up the USB-6210 to use a time-based filter but I thought a simple RC filter would be a quick solution.
I have tried this with a USB-6211 with the same results. Only the USB-6009 preformed as expected with accurate counts. The USB-6009 edge count is not affected by the RC filter.
Any thoughts?
Thanks,

goldenrad wrote:
... I'm assuming that the input should have a hysteresis mechanism ...
It doesn't . You should use the digital filter.
goldenrad wrote:
It is interesting that the filter works perfectly on the USB-6009.
It's probably a bandwidth issue, there's no hysteresis on the 6009 inputs either. The 6009 event counter can only count up to a 5 MHz signal according to its specificaitons. The 6210 however supports an "external base clock frequency" of up to 20 MHz.
Best Regards,
John Passiak

Stop and start counter set to frequency read

Original question posted in the counter forum but no response so hope its ok to try here?
I am using a 6024E interface to operate a PID loop that keeps the RPM stable of a servomotor but having problems when attempting to read frequency at the same time from a flow-meter.
Basically the operation of the system is as follows;-
User sets an RPM demand, say 5000RPM, an analog signal is sent out to the motor controller and motor runs up to this value after a brief delay. The feedback from the motor is from its shaft encoder which gives 1000 PPR, after signal conditioning in hardware this signal is applied to the gate of timer 0 and after scaling applied to a PID loop. The PID loop is quite stable and responds well to operator demands.
However the first problem was noticed when the RPM demand was taken to zero and an attempt to halt the program was made. There was a delay in shutting down that was roughly equiv to the time out value which was set on the DAQMX read Vi.
Things became much worse when a further loop was added to read a flowmeters frequency output (approx 50 to 300Hz max, counter 1) that varied with the servo motors RPM demand. This additional routine has almost stopped the whole program initially starting as it appears that counter channel 1 is waiting for an input before letting the rest of the program run.
I have attached the part of the program that I am using now to read the frequency of the flow meter, similar routine also being used to monitor the RPM of the servo motor.
Basically when the operator increases the RPM demand and reaches a demand of 10RPM a compare function places an output line, which is connected to the input OPR1/PFI7 (see attached vi ) to logic 1. This then triggers the counter to start reading the RPM of the motor. A similar method is used for the flowmeter but in this instance it does not try to read the flow until the motor has reached 3000RPM as the flow being measured is very low and below 3000RPM it is only about 2cc/min = 40Hz.
Problem occurs though when the RPM is reduced to zero and the flow/RPM stops. If the RPM demand is increased again the motor sometimes will not respond and suffers delay. Removing the loop for the flowmeter cures this problem. Seperate loops are used for the flowmeter, motor RPM and PID loop that controls the motor RPM.
The problem, as I see it, is that I need to be able to stop the counter for the flowmeter aquiring data when it falls below a certain value but be able to restart it again when the the flow increases?
Also is there any way I could sync the analog output signal (motor RPM demand) to the counter freq read signal (motor encoder feedback)? I found examples in the help files for this but using 'count edges' not frequency or period mode.
Thanks John
Labview Version 8.5
Labview Version 8.6
Labview Version 2013
Attachments:
arm triggerver1.vi ‏38 KB

Hello,
First of all thanks for posting on our forum.
I may be lazy but I think your question is very long and not very clear... Next time try to be more precise and to post shorter messages, this is just an advise, but short questions often get quick answers.
now let's talk about your problem, the first thin I'll say is why don't you use NI-Motion hardware, that would be really appropriate to you application, then if you can't (which I understand) you should really use Real-time programming, when you're using a PID, real time is really advised.
My only question will be : What is the problem? can you be a little bit clearer? what can we do for you?
I'm sorry but I'll really be glad to help you but so far I did not understand.
Regards
Richard Keromen
National Instruments France
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DAQmx non-cumulative buffered edge counting (like the PMT TTL problem) with PCI6221 in C program environment

I have a PCI-6221. I am programming in C/C++ and DAQmx. My application is much like the previous thread counting the number of asynchronous TTL pulses from a PMT in some user specified time interval. The time interval is typically around 1 msec and the signal rates are around 1-10 kHz. So I expect to count 0 to 10 pulses per timebin. In traditional DAQ this was called Non-cumulative buffered edge counting.
To get a clock at about 1kHz, I first create an "analogue in" task that samples at 1kHz. The only thing I use this task for is to route its sample clock to the gate of the counter. This defines my time interval as 1 msec.
I then create the counter task. I am using count edges. So I think counter0 gate = PFI9 and source = PFI8.
DAQmxCreateCICountEdgesChan(*taskHandle,chan,"",edge,initialCount,countDirection);
DAQmxCfgSampClkTiming(*taskHandle,clockSource,rate,DAQmx_Val_Rising,DAQmx_Val_ContSamps,samplesPerChan);
where clockSource="/Dev1/ai/SampleClock"
I apply my signal to PFI8.
After starting the task, I read an array of values with
DAQmxReadCounterU32(taskHandle,samplesToRead,10.0,data,samplesToRead,read,NULL);
I expect the array data to have values ranging from 0-10 for PMT input with an average rate of about 10 kHz. The trouble is that the array data does not seem to make sense. I get constantly increasing values. For very low input frequency, it just increments by one per array member.
More troublesome, when I hold PFI8 at ground, so that I expect zero pulses to be counted at the source for each edge at the gate that occur 1 per msec, I get a timeout error. I really must be able to count zero events per bin.
Am I doing something obviously wrong?

Hello,
The behavior of non-cumulative event counting is equivalent to period measurement. Additionally, the timeouts when no edges occur on your event counting terminal are the result of duplicate count prevention. In DAQ 7.4, the default behavior of duplicate count behavior should take care of this for you, but if you cannot upgrade to DAQ 7.4, I'd do a search of the discussion forums for "duplicate count prevention". There are a number of previous posts about this attribute, including this one.
If you aren't using the second counter on your device, you should be able to use the Period Measurement 2 Counter High Frequency measurement method to get your desired values. The "Measurement Time" attribute in this case would be the "sample clock" (1 kHz in your example). Then just raed the data raw to get counts rather than scaled.
If you'd like to do it using the AI timing engine. Configure a 1 counter period measurement task, use "clockSource" as your input terminal and use your PMT TTL pulses as the "Counter Timebase Source". Then read the data raw, since the scaling will not be appropriate for your needs.
I hope this helps!
gus....

Error -200429 DAQmx read (counter u32 1ch 1samp).vi -append- Edge count in for loop

I am receiving error -200429 DAQmx read (counter u32 1ch 1 samp).vi <append>. This is occuring on the second loop of a for loop.
I have a sequence inside the for loop that is using four DAQmx assistant vi's for edge count at various times in the sequence. All four of these count fine the first time through but at the beginning of the second loop the first edge count receives this error and does not count.
Any ideas?

The code you have supplied is similar to the converted subvi but this code will give an empty task error on the DAQmx Create Channel vi.
Notice on the Daqmx create task vi that there is nothing wired to the "Task to copy" or the "Global virtual channels" connectors - I believe this is why the task is empty when sent to the Daqmx create channel vi.
The code we are currently using is a modification of a previous code used before a recent upgrade. It may be better in your/NI eyes to re-write this into a State machine but time constraints and resources do not allow that at this time - All other parts of the current program work except for the counter on the second iteration. Would rather not reinvent the wheel at this point.
If the task is being cleared was the issue then the other three should also not execute. The issue appears to be the "First Call"
I have attached a zip file of the complete program as it is now written to give you a better idea of the whole picture.
Attachments:
Test Machine current code.zip ‏657 KB

How do EDGE charges work/where do I look for itemized billing GoPhone Pic

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http://www.lindenlan.net/2007/08/15/prepaid-vs-contract-att-gophone-or-nation-pl an/
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Every other day I was oscillating between being extremely pleased with my purchase and then chastising myself for spending all the money on the service that I was sure would be inadequate. I don't call much and considering how fast things are changing I don't want to be locked into a two year contract though I understand Apple is locked into five years exclusively with AT&T.
I hope good things come your way !
Message was edited by: barkingmad

Ctr0 Edge Counting Issue

I have a PXI-6602 and am writing a C++ class to control the card. I am experiencing an issue when using ctr0 for edge counting. My setup includes one PXI-6602 and a BNC-2121. I'm using the continuous pulse signal as the source signal to the counters. My software execute the following functions in order.
// Clear any old tasks
DAQmxClearTask( TaskHandle );
// Create new task
DAQmxCreateTask( "ctr0Task",
                          TaskHandle );
// Setup channel
DAQmxCreateCICountEdgeChan( TaskHandle,
                                            "\CTR1\ctr0"
                                           DAQmx_Val_Rising,
                                            0,
                                            DAQmx_Val_CountUp );
// Start Task
DAQmxStartTask( TaskHandle );
// Read counter value
DAQmxReadCounterU32( TaskHandle,
                                 DAQmx_Val_Auto,
                                 10,
                                 buffer,
                                 sampsRead,
                                 NULL );
I execute the above code and let the task run for approximately one second. I read one sample of zero (0) counts on ctr0. When I execute the same code for the other counters, I read around 464 counts, which I believe to be valid.
Why am I reading zero counts on ctr0?
I have tried the following:
1) Using the Test Panel, I setup ctr0 for edge counting and used PFI39 (ctr0Source) as the source signal and everything worked as expected. So I know the hardware is working. I also selected the 20MHzTimebase signal as the source and everything worked as expected.
2) I manually setup a task within NI-MAX and everything worked as expected.
3) Within my software, I routed the 20MHzTimebase signal to ctr0 source and received counts although the value was incorrect. No matter how long I let the task run, I would only read around 260 counts. When routing the 20MHzTimebase to one of the other counter's source, everything worked as expected.
4) I also routed PFI39 to the source of the other counters and everything worked as expected.
Is ctr0 special or reserved? Does it have a unique timing characteristic that I'm unaware of?
Thanks in advance for any help.
-Mroche

Hey
There should not be any issue. I have that board and used that in lv, but try the attached code and see if this works.
lab
Attachments:
Count Digital Events.zip ‏56 KB

Buffered Edge Counting 20 MHz with duplicate count prevention

Dear all,
I went through the specs of several boards (M- series, S- and E- series, 6602 etc...). It seems that these boards can count edges with duplicate count prevention on at a maximum rate <= 20 MHz (i.e., 1/4 of 80 MHz) - but maybe I have misunderstood the docs.
Is there a NI board capable of buffered edge counting with a general purpose counter for random events going at rates from 0 Hz to > 20 MHz? Do I need to look for a reconfigurable board?
Thanks in advance.

Dear Elizabeth,
Thanks for the answer.
In my application, events arrive asynchronously (actually, randomly). During the duration of a gate (namely, 1 microsecond), one expects anything from 0 to many (i.e., possibly more than 20, up to 80) events. This requires duplicate count prevention.
I may have misunderstood the specs for M series boards, but the document:
Using Duplicate Count Prevention for Counter Tasks in NI-DAQmx
from the NI web site, for instance, states that:
"All the other timebase edges that occur while the external source input is high are ignored. If no source edges are detected between two gate edges, as shown in Figure 3, duplicate count prevention ensures that pulse measurements return zero because the external source must be logic high to allow the internal timebase to increment the count register. This reduces your maximum source frequency to quarter of the original maximum (80MHz) timebase for NI-STC II and NI-TIO boards. Therefore duplicate count prevention should only be used if the frequency of the Source signal is 20 MHz or less.
Duplicate count prevention should only be use in the following situations:
Counter measurements
The counter Source is using an external signal (such as PFI x)
The frequency of the external source is 20 MHz or less
What's your take on that?
Thanks for your time.

Timestamp edge count

Hi. I am very, very new to Labview. In fact, I am working on my first program so my question is probably really simple, and I bet I overlooked the question when reviewing previous posts. Here it goes. I am using LabVIEW 8.2 and I have some tipping buckets which collect data through an analog edge count. I would like to timestamp and record the data only as it occurs. I have figured out how to continuosly save the data without a timestamp, but this is problematic because this will create an extremely large file due to the time requirments. I will post a screen shot of my code. Thanks!

Hi,
I'd like you to also expand on how you're collecting your data. What do you mean by "analog edge count"? I don't know what kind of signal you're measuring. Is it an analog signal, and if so, what are these 'edges'? Most of the time, counting edges means counting digital edges, so 0 to 5V rising edges or 5 to 0V falling edges.
At any rate, I'd like to explain a little bit about how a DAQmx task works, and I'm assuming you're continuously measuring analog signals with an analog input task. When you start an acquisition, the board will use the sample rate you specify to grab samples from the analog inputs. If you specify a continuous acquisition, it will continue to grab samples until you end the operation. Regardless of whether or not the signal value changes, the board will grab samples at the same rate. If you only care about when the signal's value changes, then you'll need to read your data and only record it to file when it does change. In that case, Ravens Fan is correct, and you'll need to do some simple post-processing to save the data of interest to you.
Joe Friedchicken
NI VirtualBench Application Software
Get with your fellow hardware users :: [ NI's VirtualBench User Group ]
Get with your fellow OS users :: [ NI's Linux User Group ] [ NI's OS X User Group ]
Get with your fellow developers :: [ NI's DAQmx Base User Group ] [ NI's DDK User Group ]
Senior Software Engineer :: Multifunction Instruments Applications Group
Software Engineer :: Measurements RLP Group (until Mar 2014)
Applications Engineer :: High Speed Product Group (until Sep 2008)

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Invalid values for negative counts using DAQmxReadCounterF64 for edge counting

I am seeing this issue with using DAQmxReadCounterF64 with
simple edge counting. If the counter reads a negative count value, it
returns a number that looks like an unsigned 32-bit number rolled over
(~4294967295).
I am using DAQmx v8.9.5. PXI-6602 with Windows XP, programming in C++.
Is this a bug in the driver?

Hi Mroche,
You're correct that the number you are seeing is the rollover of an unsigned 32-bit integer. Newer DAQ products use a 32-bit count register (e.g. M Series, TIO, X Series). In this register, the value -1 is represented the same as 232-1.
I wouldn't call this a bug exactly. The value you are reading is what is in the count register, and I don't think it makes sense to necessarily assume that 4294967295 should be scaled to -1 for all cases. Making this assumption would result in undesired behavior for anybody trying to count to 231 or higher (at which point the count would roll over to -231).
Having said that... position measurements are treated differently starting in DAQmx 9.0 due to the behavior reported on another thread which was in fact deemed a bug (which I notice you have seen already). The driver casts the raw count to I32 before scaling it to a position.
Now, I'm not so sure it makes sense to treat the two measurement types differently, but I think the reasoning behind the decision was that negative values make sense when talking about position, but for counting edges not quite as much (what exactly is a negative number of edges?). In the count edges case, I think it makes the most sense for DAQmx to allow the user to handle rollovers himself. At the end of the day, all the driver can do is change where the rollover occurs (either at 0 = 232 or 231 = -231).
In your case, if you want to read (-) values on your count edges task, the easiest way to accomplish this is to read the data back as U32 (DAQmxReadCounterU32) then type cast it to I32. This will give the result that I think you are looking for.
If you have any suggestions to help improve usability, please feel free to post to the DAQ Idea Exchange. Some preliminary ideas to make this experience a little more intuitive might include a property node to set how the data is cast, or perhaps have the driver cast the data to I32 if the Count Direction is set to anything other than Count Up. Although, the 2nd idea has the potential to break existing applications so it might not be as viable of an option.
Best Regards,
John Passiak

How to make Edge Animation works in HLTM5 Offline? I cache all files, but Edge didn't play.

How to make Edge Animation works in HLTM5 Offline? I cache all files, but Edge didn't play.
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Thanks!
Astors

Thank you for your answer.
I do use cdn off for publish setting.
The Web site that I am working on is a very complicated site. Edge
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When server is offline, I get all files from Appcache without problem,
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I Google hundreds time, cannot find answer on why this file is always get
online.
Finally, I find out myself, Adobe Edge don’t like relative file path for
*_EdgePreload.js.
Change to root absolute path fixed the problem:
Astors

NI 9402 edge counter works, no frequency though

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