There are different technologies available to eliminate long home runs of thermocouple extension wire and the associate error caused by the wire. A popular choice is to DIN-rail mount HART temperature transmitters in the field and then bring the copper wire back to the DCS input cards.
By today’s standards, there is no need to have these data acquisition points consume all those DCS analog input cards. It is quite simple to convert these temperatures to MODBUS/TCP and bring them into the DCS via Ethernet.
The mechanics of making this conversion are 1) put the HART transmitters into a digital mode and 2) using DIN-mount terminal blocks wire the transmitters into a HART network of 16 transmitters each. The Moore Industries HES HART to Ethernet Gateway System is the HART to Ethernet converter capable of being the HART master for four networks. One HES gives you 64 temperatures converted to MODBUS/TCP, unless your transmitters have dual inputs, in which case the count would be 128 temperatures from one HES.
- Keeping the signal digital increases accuracy and saves money
- Mounting temperature transmitters in junction boxes close to the process unit reduces thermocouple extension wire and all the associated problems
- Converting your HART signals to Ethernet saves or repurpose all those analog inputs cards