They are the M-11 series from SKH. My company has over 300 units installed, using these boards, but it seams like the troublesome units are located in the New England/New York area.
We are thinking that it may be EMI or RF causing it, but we have been unable to simulate the failure in the lab.
I currently have several plc units that have the program settings stored in ram memory that is backed up by a 3v lithium cr2430 battery whenever the power is lost. These units are starting to loose the settings or have the settings stored in memery change intermittently. There is no apparent...
