Greetings! While not new to AB PLCs, am to their Micrologix line and this forum; appreciate insight from with experience those along these lines ...
Have been programming and testing a ML 1100 in lab for deployment to field app (along with other unrelated project tasks) without any major difficulties for past several months. Last weekend while "stress-testing" system (e.g., a few inputs running over weekend to ensure robust operation once deployed to remote mountain location), it appears that the DC power supply (PS) simulating an analog input failed. The decades old power supply was dark when observed Monday; once replaced with a new PS, attempts to simulate anything more than about half-way through its 0-10 VDC range failed. Subsequent troubleshooting (after attempting to place a 1 M-ohm resister across inputs and then getting the other analog input to work, with or without the external resistor), showed the specified ML 1100 internal input resistance down from 210 K-ohms to around 300 ohms. Other channels (the other analog and various digital) working fine. Internally the old DC PS appeared fried.
I couldn't find any further troubleshooting assistance for the ML 1100. Does anyone know of any? Is there any alternative to replacing it? While there appear to be no lightening strikes in the vicinity, and the PS was old, I'm still not sure of the cause -- and am wondering how to prevent similar incidents in the future. Your insights are greatly appreciated!
Brad
Scientist, US Navy
Have been programming and testing a ML 1100 in lab for deployment to field app (along with other unrelated project tasks) without any major difficulties for past several months. Last weekend while "stress-testing" system (e.g., a few inputs running over weekend to ensure robust operation once deployed to remote mountain location), it appears that the DC power supply (PS) simulating an analog input failed. The decades old power supply was dark when observed Monday; once replaced with a new PS, attempts to simulate anything more than about half-way through its 0-10 VDC range failed. Subsequent troubleshooting (after attempting to place a 1 M-ohm resister across inputs and then getting the other analog input to work, with or without the external resistor), showed the specified ML 1100 internal input resistance down from 210 K-ohms to around 300 ohms. Other channels (the other analog and various digital) working fine. Internally the old DC PS appeared fried.
I couldn't find any further troubleshooting assistance for the ML 1100. Does anyone know of any? Is there any alternative to replacing it? While there appear to be no lightening strikes in the vicinity, and the PS was old, I'm still not sure of the cause -- and am wondering how to prevent similar incidents in the future. Your insights are greatly appreciated!
Brad
Scientist, US Navy
