Emerson Rosemount 644 HART, Справочное руководство

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2
Reference Manual
00809-0100-4728, Rev MB
Introduction
July 2016
Introduction
1.2 Transmitter overview
The Rosemount 644 Head Mount Temperature Transmitter supports the following features:

HART configuration with Selectable HART revision capability (Revisions 5 or 7)

Accepts either 1 or 2 inputs from a wide variety of sensor types (2-, 3-, and 4-wire RTD, Thermocouple,
mV, and Ohm)

A compact transmitter size with electronics completely encapsulated in protective silicone and
enclosed in a plastic housing, ensuring long-term transmitter reliability

Optional Safety Certification Option (IEC 61508 SIL 2)

Optional Enhanced accuracy and stability performance

Optional LCD display with extended temperature ratings of -40 °C to 85 °C

Optional advanced LCD display with local operator interface (LOI) with extended temperature ratings
of -40 °C to 80 °C

Two housing materials (Aluminum and SST) and various housing style options that allow for mounting
flexibility in a variety of environmental conditions

Special dual-sensor features include Hot Backup
™
, Sensor Drift Alert, first good, differential and
average temperature measurements, and four simultaneous measurement variable outputs in
addition to the analog output signal

Additional advanced features include: Thermocouple Degradation Diagnostic, which monitors
thermocouple health, and process and transmitter Minimum/Maximum Temperature Tracking
The Rosemount 644 Rail Mount Temperature Transmitter supports the following features:

4-20 mA/HART protocol (Revision 5)

Accepts 1 sensor input from a wide variety of sensor types (2-, 3-, and 4-wire RTD, Thermocouple, mV,
and Ohm)

Completely encapsulated electronics to ensure long term transmitter reliability
Refer to the following literature for a full range of compatible connection heads, sensors, and
thermowells provided by Emerson
™
Process Management.

Temperature Sensors and Assemblies Product Data Sheet, Volume 1 (document number
00813-0100-2654)

Temperature Sensors and Assemblies Product Data Sheet, Volume 2 (document number
00813-0200-2654)
1.3 Considerations
1.3.1 General
Electrical temperature sensors such as RTDs and thermocouples produce low-level signals proportional
to their sensed temperature. The Rosemount 644 converts the low-level sensor signal to a standard 4–20
mA DC or digital HART signal that is relatively insensitive to lead length and electrical noise. This signal is
then transmitted to the control room via two wires.
1.3.2 Commissioning
The transmitter can be commissioned before or after installation. It may be useful to commission it on
the bench, before installation, to ensure proper operation and to become familiar with its functionality.