AI-111 change readings after reboot

[Damill]

We are using several cFP-1804 + AI-111 in a monitoring system. They are powered from a central UPS and works fine except when we shut the system down for service. After restart, some AI-111 modules changes all their reading several mA in same direction just as if their offset is wrongly recalculated. After software-resetting both the cFP-1804 and the AI-111 via MAX some times or by power-cycling, the values can return to normal. What is the reason and what to do?

/Dan  

[Matthew_Williams]

Hi Dan.  Interesting problem.  Are the reading improper in MAX?  We saw something very similar in RTD modules some years ago.

When powered up the modules would randomly read 4C high on all channels.  Soft reset (reset button) would always correct it,

power cycle would usually cause the problem to reappear.  MAX showed the error.  Problem turned out to be a hardware issue with

the modules.  We don't use enough AI-111 modules to have any data.  We were using cFP-2010 controllers.

Matt

[Damill]

Yes, the problem is always observed in MAX.

Software reset will fix the problem and sometimes also power off/on

We will continue by checking the power supply stability the first seconds after power on just to skip that possible cause.

/Dan