If I understand it correctly, you need
- a thermocuople input to a transmitter (which outputs 4-20mA)
- a separate thermocouple signal for something else.
both inputs coming from a single monitoring point that has a thermocouple installed.
If that's the case, all you need to do is to connect the T/C to one device and parallel another thermcouple wire (+ to +, - to -) of the same type from that T/C input to the other.
It is an accepted practice in the heat treat biz to parallel a T/C to both a temperature controller and a recorder.
There are two difficulties that can be encountered
a) If the thermocouple is grounded and inputs are not floating you can get ground loop(s). That can be resolved with dual thermocouple elements, with one element for one device, one element for the other.
b) Many devices have an "open thermocouple" or "thermocouple break" detection circuit. Sometimes those circuits conflict with one another, causing offsets or spikes when connect them with a common T/C. The solution, again, is dual thermocouple elements, with one element for one device, one for the other.
Paralleling thermocouples also assumes that the connection blocks or terminal blocks are isothermal, meaning the + and minus erminals on any given device are at the same temperature, otherwise error is introduced.
Dan