Error in long duration testing

[balajikasthuri]

Hi,

I am using a PCI 6014 card with labview 6.1 for a long duration test (expected up to 500 hrs). In my application I am using two counters to measure two shaft speeds. I am generating a common gate signal for the counters from the AO channel.

After normally running for 8-10 hours, I find that one counter value influences the other. For eg when the speed of one shaft changes from 3000 rpm to 1000 rpm, the counter measuring this speed measures correctly as 1000 rpm. But the other counter which measures a constant speed(5000 rpm) suddenly changes to around 4000rpm.

I am trying to isolate other sources and noises of this problem. I wanted to know if there could be any problem related to the time period that I run the test. If so
what is the maximum time that I can continously use PCI 6014(when all other factors like network, virus scan are taken care).

Thanks.
Balaji

In my application I measure speeds

[Bill B]

Hello Balaji,

Thank you for contacting National Instruments.

There should be no reason for one counter on your machine to affect the other counter. If the counters work correctly initially, there is nothing on the board that will cause them to create this effect after a long period of running. Basically, the counters will either work correctly or not at all.

What usually causes problem such as these is noise in the external environment. What I would try to look for is a change in your external environment when this problem occurs, such as a piece of machinery turning on or some other noise source.

Please let me know if you determine any additional information on this issue.

Regards,
Bill B.
Applications Engineer
National Instruments