Double thermocouple on controller

[Redblackviper]

Hi I need to buy 2 thermocouples and a controller, I'm curious if it's possible to connect 2 thermocouples to one controller? If so how do I connect them I need to control one item from 2 points with one controller?

[Entropy]

Not really very possible as these PID controllers have one thermocouple connection--at least i do not recall seeing a version that reads more than one (but i am not part of the company/sales staff--just a so-so customer). Wiring them together would defeat your purposes i would think as it would introduce a lot of noise/error. You could rig a special switch i suppose but it wouldn't be reliable as my understanding is that it would have to continue to use the same materials as the thermocouple types two leads--it would still work in a sense but may not be reliable as far as indication/accuracy. The general notion is that you should really minimize connections although it is typical to use a panel plug and socket in addition to the terminals on the PID--using an extension to connect the pid to one of the plug/sockets. There are special terminals available for reading multiple thermocouples --an Adam something that will run you a couple hundred i recall is the cheapest i have found to read up to 8 thermocouples--i think you would have to buy other equipment and hook it all up vias Rs485 to do anything with it--not sure but don't think it does anything more than provide temp signals to a rs485 network and you would then need a master controller of some sort--you'd have to look this up on the web.

What i can say for sure is that most folks would use two PIDs for two thermocouples. It is common where better control is desired to use one to ramp up the temperature and to rig the other to cool to minimize overshooting and allow better control according to the profile. (This is necessary due to response lag times of thermocouples and particularly heaters which don't just immediately shut down to zero). Incorporating a cool down is more accurate than trying to account for the lag--for a lot of people it isn't critical and they don't need it. My own opinion is that 2 PIDs would be simpler and easier to set up and operate for most folks unless you are really sharp at the comm end of things. Probably no cheaper reliable way.