Signal Isolator Burnt

Over voltage and over current are the first things that comes to my mind. Now the source of these over voltage and over current energies will be kind of hard to guess from what you've given us. This could be due to a lightening strike. A wire may have accidentally been plugged into the wrong circuit. You may have irritated somebody enough that they deliberately plugged it into the wrong circuit. I'll bet you it was that guy at work that you get all of your brilliant ideas from. It might be that you've been exceeding the isolation voltage values for too long. Eventually the manufacturers specifications will teach you to notice them.

Then there are the non-electrical possibilities. When using any aromatic solvent including alcohol to clean the flux off of a circuit, do not immediately power the circuit. A blow torch should not be used to test a power supply's thermal stability. All electronics found in the remains of a house fire, will probably have these type of burnt markings.

Dear Guest,

Redfred is right. Think of it this way. The isolator was placed to prevent "ground" current from flowing in the analog system between the transmitter powered from your auxiliary 24v dc supply and the remainder of your system. In some systems it is obvious why an isolator is needed, for example measuring buss temperature on a 600 vdc electrical buss. A nearby lightning strike might pulse causing a ground swell adding and subtracting 1500 volts or more in addition to the 600 volts on the buss bar. It may not happen again in a lifetime or it may occur tomorrow even larger especially if you are in Florida or Texas. If these things happen a lot you could consider placing a counterpoise around the entire SCADA network, or maybe a well placed 12' grounding rod will do the trick for you. Then there is the threat of a direct lightning strike, what damage could that do?

Luther M