Synchronizing the read of two timer tasks (Period and Two Edge Separation)

Hello,
I am using labview 2011 and need to latch the data from two timer tasks of a 6602 board at the same time and then perform the read. One task is a period measurement the other is a two edge speration. It sounds pretty simple and I am sure it is, I just haven't located the correct information yet, If someone would point point me in the correct direction.
Thanks,
Mike

While it's true that a digital edge arm start trigger can help to sync the tasks to begin together, the nature of the measurements you're making also have a big impact on whether you can depend on the buffered data remaining "synced." Both measurement types will latch measurement data at times determined by the signal(s) being characterized. You cannot configure either task type to sample at a known constant rate. You can only accept samples at the rate dictated by the signals' own edges.
Ok, so having said all that, here are some implications:
1. a cumulative sum of all your period data will effectively give you timestamps for all the active edges, with t=0 set by the arm start trigger edge.
2. there is no information inherent in a two edge separation measurement that can identify the time relative to the arm start trigger. You'll get a bunch of measured interval times with completely unknown times between those intervals
3. caveat: if you are somehow using the same signal edge for both measurements AND getting one measurement of two-edge separation for each and every period measurement, ONLY then would you be able to reconstruct the timestamps relative to the arm start trigger edge.
So I'd caution you that the idea of latching readings in sync or reconstructing relative edge times between the measurements is pretty unlikely to work except under some very specific circumstances.
-Kevin P

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Hello,
I have encountered a strange behaviour of the NI6602 Counter/Timer.
When I use the C# Meas2EdgeSeparation example as provided by NI, I am only able to have correct time measurement on channels 1 and 2. For the other remaining 6 channels the time will always be measured immediately when I only have a start signal, the stop signal is not required. This results in a measurement of 1.25 e-8 s, being the minimum value of this counter. It seems that the start signal is also seen as stop signal, but Two Edge Separation should not have this.
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I use a NI 6220 board and want to perform something very similiar to what is described in the knowledgebase article "How Do I Count Digital Edges Between a Start and Stop Trigger on an NI 6602 Counter/Timer Board?".
Does anybody know how I have to change the example program "TwoEdgeSep.c" to use not the internal timebase but to use an external source (the one I want to count the edges?
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Solved!
Go to Solution.

What errors were you getting?
The counter can count between 2 and 232-1 ticks. So... the rate that you specify will determine the minimum and maximum value (in terms of seconds) that you can count. These values are set when you create the channel:
It seems intuitive to try to put "0" for the minimum value, but that will give you error -200527 (Requested values of the Minimum and Maximum properties for the counter channel are not supported...). The real minimum value (in seconds) should be no less than 2 * (1/ timebase rate). I'm not sure if this is your issue or not, I'm just speculating.
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Synchronizing the read of two timer tasks (Period and Two Edge Separation)

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