Guest Mel Posted January 29, 2004 Report Posted January 29, 2004 Hi. I am a intrument tech at a papermill. Today we had a occurance that very well could of took down both paper machines in the mill. Our air pressure got below 60 psi. Fortunately one of our mechanics had the forsite to put the valves in the needed position to make the needed air. It all comes down to a card on a allen bradley PLC500 card that was bad. We had one in a rack in a trainer that occaiaionaly gets used. When we swapped out the apparent card, which was a analog input/output card with a replacement. It had the same problem. After this we were checking elsewhere. After a few hours we came back to the card and had to send for one at our Allen Bradley distributer. We don't stock one thinking that we are saving money and that we can get it from a distributer in a short time. Well here is the idea. What was needed is a program that we can test all the different cards that we have. We have made a trainer for inputs and output switches and lights. What we need is a program that we can check the several analog cards to know and not guess if they are good or not. I was thinking if I had a program for each of the cards and just to slip that card only in the rack and load the correct program and put that card to the test. Almost seems like a no brainer. It seems analogs can do some flakey things. Please tell me what you think. I know we have the resources. This old card just sat in the trainer defective and we never knew it. Thanks for hearing me out. Mel Quote
Sleepy Wombat Posted January 29, 2004 Report Posted January 29, 2004 Have u got the new card from your AB distributor and installed it yet ? Has it got the same problem also ? If so it could be a transducer problem.... Also I test analogue signals with a loop calibrator from Yokogawa...This enables me to simulate 0-20mA, 4-20mA, 0-10V, 1-5V and also measure them accuratley, i can compare this to what the PLC is reading and determine what is going on... Quote
Guest Mel Posted January 30, 2004 Report Posted January 30, 2004 The card that was in the trainer was one that was defective and just stuck in there. The card we got from AB worked fine. That is why I was wanting to build something to test analog cards and prove that they were ok. I would be interested in how to check them out. I thank you for your help. Quote
JimRowell Posted January 31, 2004 Report Posted January 31, 2004 Sleepy Wombat's suggestion of using a handheld tester probably makes the most sense but another possibility would be to tie cards together and make them test each other. Make an analogue output feed each analogue input. You could then programmatically vary the output from low to high and verify that the inputs agree with what the output is supposed to be. If all inputs claim the output is wrong, you know you have a bad output. If only one input disagrees, then you have a bad input. Something like that. I'll leave the details to you. Jim Rowell Quote
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