We have three TC-08 usb dataloggers running, each has several thermocouples connected and one module each for mv logging from a CT with mv output. We use Transformers to create current flow in each of the three loops and thus monitor current with the mv signals and temperature at intervals eleswhere on the three seperate loops. We use multi channel session logging and have done so for many years. I now have an unfamilar temperature signal when we switch in the third Transformer and input 300 amps, the temperature on the third TC08 drops by 10 degrees, when the transformer is on its of cycle everything jumps back up? The other two loggers work with no issue during there seperate on/off cycles. I have tried changing channels, thermocouples, tc-08, mv modules to no availe? It only occurs when the third transformer kicks in? The transformers are controlled by a refernence thermocouple on each loop, one of the thermocouples is in contact with the cable core as it needs to measure the core temperature, this goes through the Tc08, the transformer thermocouple is in contact with the sheath and is fully insulated. I believe the contollers, pc, transformers and TC08 are on the same earth loop. So before i switch over the transformer controller is there anything else I may need to consider? Any pointers would be appreciated.I have done this many times before with no issue, unless there is an earthing issue I cant think what is causing this.