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

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I hope this helps!
gus....

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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.
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Test Machine current code.zip ‏657 KB

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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.
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I have tried the following:
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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.
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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

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Hi there,
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Applications Engineering Team Leader | National Instruments | UK & Ireland
Attachments:
VBcode.txt ‏4 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.
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Using Duplicate Count Prevention for Counter Tasks in NI-DAQmx
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"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.
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What's your take on that?
Thanks for your time.

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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.
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Joe Friedchicken
NI VirtualBench Application Software
Get with your fellow hardware users :: [ NI's VirtualBench User Group ]
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Senior Software Engineer :: Multifunction Instruments Applications Group
Software Engineer :: Measurements RLP Group (until Mar 2014)
Applications Engineer :: High Speed Product Group (until Sep 2008)

Edge counting buffer/array size problem (VC++)

Hello,
I accidentally posted this in the multifunction DAQ forum so forgive me for posting this again here.
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Go to Solution.

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I have using an 9215A USB (4AI).
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Henrik
LV since v3.1
“ground” is a convenient fantasy
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Cas
Solved!
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