problem with PCI-6602 "Counter in" and "Digital Out"

[Michael Kneisel]

Hello,

I have a Problem with my PCI-6602 and LabView 8.2 (DAQmx 8.71). I want to measure the period and the pulse width of 4 PWM signals (about 1kHz)  from sensor. I do this with the eight counters on the PCI- Card, this works fine. The Problem is, that I have to add a digital Output to synchronize this PC with another one. This should happen over the falling edge of the digital output signal. I am able to generate the output signal, but the problem is, that the measurement of the counter changes. I do the same thing with the sensor, but I get different measurement results.

You could see this in the pictures I attached. The  4 graphs on the right shows the input signals, which are in both picture nearly the same. The graphs on the left (moment 2/3) are different, although the maths in the VI is the same.

I hope, I could communicate my problem.

Bye Michael

[DanielHermyt]

Hi Michael,

I think we should break your VI to find the cause for the error.

If you look at the "raw" counter inputs, are the signals OK?
Please try to reduce your code to a minimum of inputs to get e.g. the "Moment". Does the error still occur?
When you look at the test panels in the Measurement & Automation Explorer, does the error occur there too?

What device is connected to your PCI-6602?

[Michael Kneisel]

Hi Oyster,

thanks for your answer. In the last week I found the error in the VI. The counters were not synchronized to each other, they started at different times. At this time I only put the "start" in a case structure, so that all tasks were created. The Problem is that the CPU is not able to genereate all starts at the same time and because of this the counters were not sync. After reading in the forum I found the method to use an arm start trigger. But I was not able to generate a trigger for all channels, if I run the VI nothing happen. In an example on the ni HP I found a method to generate the whole task in a loop and then I was able to trigger all 8 counters and start them sync to each other.

I attached the new VI, if somebody else has the same probolem.

Bye Michael