Introduction 1
The TX91 two-wire transmitter receives and measures signals from thermocouples and sends an output current of 4-20 mA which is directly proportional to the thermocouple millivolt input. It is designed to connect with only two copper wire leads that will supply the voltage to operate the transmitter from a DC power supply, and also carry the output current. The output current is then used for recording, computing or controlling.
If the TX91 is mounted inside a protection head, such as the OMEGA NB1 Protection Head (see Figure 3-1), the thermocouple extension wires are replaced by two copper wires that carry the 4-20 mA signal and DC voltage to operate the transmitter. (Refer to the OMEGA Temperature Handbook for information on NB1 Thermocouple Assembly.)
