On Fri, May 29, 2009 at 12:16 AM, Electron wrote: > 2) as although I love my grandpa I don't have the time, expecially now, > to redesign everything from scratch, but only to improve on the existing > design and rebuild 3 new dataloggers, I'd also like to keep the existing > PCB's I have if possible. This means that the datalogger remains, in > substance, hundreds of meters of cables that run, through a shunt and a > 10K resistor, directly into each of the 7 channels ADC pins. A weak design, > BUT could it work if I improve on the external lighting protection instead? Do you have necessary protection like TVS for your data logger input? That would help. A fuse, a resistor and a TVS could do a lot of good things. > 3) the GDT You should be able to find suitable GDTs from vendors like Bourns. You may get some more information about lightening barrier here (from my previous employer) http://www.am.pepperl-fuchs.com/products/productfamily.jsp?productfamily_id=1327 The lightening barrier is more than the GDT though. They have inductors, TVS, capacitors, resistors, etc. My colleague did the design years back and I was not so familiar with it. > 4) Should I add GDT's (and copper piles) even near the sensors, or at the > datalogger side it is enough? Which is more precious? I guess it is the data logger. But as others have pointed out, the long cable is the issue. You may want to use the suggestions like Wireless or Fiber Optic. -- Xiaofan http://mcuee.blogspot.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist