Emerson Rosemount 648, Reference Manual

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Table 2-1: Examples of Approximate Basic Error
(continued)
Sensor input Approximate basic error
3-wire RTD Error in reading is equivalent to unbalanced lead wire resistance
(2)
2-wire RTD Error in reading equivalent total lead wire resistance
(1) Independent of lead wire resistance up to 5Ω per lead.
(2) Unbalanced lead wire resistance is the maximum resistance differences between any of two
leads.
Figure 2-1: Sensor Wiring
Thermocouple/mV 4-Wire RTD and Ω
3-Wire RTD and Ω 2-Wire RTD and Ω
Figure 2-2: Sensor Connections
1 2 3 4 1 2 3 4
1 2 3 4 1 2 3 4
2-wire
RTD and
Ω
3-wire
RTD and
Ω
4-wire
RTD and
Ω
T/C and mV
Note
Emerson provides 4-wire sensors for all single element RTDs. Use these RTDs in 3-wire
configurations by leaving the unneeded leads disconnected and insulated with electrical
tape.
Configuration Reference Manual
May 2020 00809-0200-4648
12 Rosemount 648 Wireless