We have an application in which we use some FP-AI-111 modules along with a network interface FP-1000 to monitor temperature and relative humidity signals. The system has been working well for years, but recently some problems have been detected.
In random occasions, one or more modules stop updating the signal values. Despite the signals do change, the module reports a constant value for hours in all the channels, like if all the channels "freeze". Somehow, after some hours, the channels "thaw" and the channels start updating the signal values again.
If someone detects the failure before it fixes itself, a power cycle restores the system. But this is unacceptable since the system must log the signals 24/7 and show the real values.
In MAX the channel status appears OK and no error is reported. This behavior may happen in any of the 6 AI-111 modules that conform the system. We've double checked the connections and changed modules position, but the problem still shows.
What could be causing this problem?
Any ideas are appreciated.
Thanks in advance.
I faced the same problem with my AIs in the project. Variable Freq Drive (VFD) feeds Analog Signals to the AI-111 card as 4-20 mA
We faced variation of signals beyond its limit, If the signal crosses the limit (4-20 mA) Distributed System Manager. shows Limits Reached or something. As per my experience if the signal goes below 3 mA or above 21 mA, the channel with freeze.
I have checked with NI lot of time about this issue and i havent received any convincing solutions...so to avoid this situation we altered the signals from the VFD.
Hope this help!!!
I've been having similar problems with the AI-111 module. My VI starts up with FP read commands to read the current output from several flow meters. It randomly reads an incorrect value and becomes frozen to that value. I would have to restart the VI to get it to read correctly. This problem also happens randomly during operatoin. I haven't found much help on the NI website about this problem.