62
Reference Manual
00809-0200-4728, Rev SA
Operation and Maintenance
July 2018
Operation and Maintenance
Grounded thermocouple inputs
Option 1
1. Ground sensor wiring shield at the sensor.
2. Ensure the sensor wiring and signal wiring shields are electrically isolated from the transmitter
housing.
3. Do not connect the signal wiring shield to the sensor wiring shield.
4. Ground signal wiring shield at the power supply end.
A. Sensor wires
B. Transmitter
C. Shield ground point
4.3.4 Wiring with a Rosemount 333 HART Tri-Loop (HART/4–20 mA
only)
Use the dual-sensor option Rosemount 644 Transmitter that is operating with two sensors in
conjunction with a Rosemount 333 HART Tri-Loop
HART-to-Analog Signal Converter to acquire an
independent 4–20 mA analog output signal for each sensor input. The transmitter can be configured to
output four of the six following digital process variables:
Sensor 1
Sensor 2
Differential temperature
Average temperature
First good temperature
Transmitter terminal temperature
The HART Tri-Loop reads the digital signal and outputs any or all of these variables into as many as three
separate 4–20 mA analog channels. Refer to Figure 2-6 on page 14 for basic installation information.
Refer to the Rosemount 333 HART Tri-Loop HART-to-Analog Signal Converter Reference Manual
for
complete installation information.
Power supply
An external power supply is required to operate the Rosemount 644 Transmitter and is not included. The
input voltage range of the transmitter is 12–42.4 Vdc. This is the power required across the transmitter
power terminals. The power terminals are rated to 42.4 Vdc. With 250 ohms of resistance in the loop,
the transmitter requires a minimum of 18.1 Vdc for communication.
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