Siemens 7MF4333 User Manual page 19

UMSITRPDS3-1
A transmitter can operate in either analog mode or digital mode, as discussed in the following paragraphs.
Analog Mode
A single transmitter is connected to a controller, recorder, or other field device. A loop known as a Point-
to-Point network interconnects the instruments. Figure 1-5 shows a traditional application.
Differential
Transmitter
®
The HART (Highway Addressable Remote Transducer) protocol is used for communication between the
transmitter and a HART Communicator, a personal computer running configuration software, or another
remote device. This is done by superimposing the HART digital signal on the analog current. HART
communications can be used to transfer a new or edited configuration, remotely monitor the process
variable, or service a transmitter.
Digital Mode
Up to 15 transmitters can be parallel connected to a Multi-Drop network using only shielded, twisted-pair
cable. The HART protocol provides communication between the transmitters and a HART-compatible
controller, recorder, or other device. Each transmitter is identified by a unique network address that is
selected during configuration.
Display, Magnetic Pushbuttons, and Loop Connections
The optional display (Figure 1-6A) permits local viewing of input and output variables and status
messages, and it simplifies local configuration. Local configuration is performed using three magnetic
pushbuttons that are found beneath an access cover in the transmitter housing. Section 6 On-Line
Configuration and Operation describes use of the display and magnetic pushbuttons.
Loop connections are made to a terminal assembly with three screw terminals (Figure 1-6B). The
assembly is located within the transmitter enclosure and is accessed by removing the enclosure cap
adjacent to FIELD TERMINALS on the enclosure. The terminal assembly also has Analog Output Test
Terminals to connect an external digital milliammeter for loop troubleshooting and transmitter
calibration. Loop wiring is shown in Section 4 Installation.
November 2010
2-Wire
4-20 mA
Model 353
Flow
FIGURE 1-5 Traditional Application
Process Automation Controller
2-Wire
4-20 mA
I/P
Model 771
Introduction
1-7