SITRANS T measuring instruments for temperature
Transmitters for rail mounting
SITRANS TW
four-wire system, universal, HART
3/38
Siemens FI 01 · 2010
3
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Overview
The user-friendly transmitters for the control room
The SITRANS TW universal transmitter is a further development
of the service-proven SITRANS T for the 4-wire system in a
mounting rail housing. With numerous new functions it sets new
standards for temperature transmitters.
With its diagnostics and simulation functions the SITRANS TW
provides the necessary insight during commissioning and oper-
ation. And using its HART interface the SITRANS TW can be
conveniently adapted with SIMATIC PDM to every measurement
task.
All SITRANS TW control room devices are available in a non-
intrinsically safe version as well as in an intrinsically safe version
for use with the most stringent requirements.
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Application
The SITRANS TW transmitter is a four-wire rail-mounted device
with a universal input circuit for connection to the following sen-
sors and signal sources:
• Resistance thermometers
• Thermocouple elements
• Resistance-based sensors/potentiometers
• mV sensors
• As special version:
- V sources
- Current sources
The 4-wire rail-mounted SITRANS TW transmitter wire is de-
signed for control room installation. It must not be mounted in
potentially explosive atmospheres.
All SITRANS TW control room devices are available in a non-
intrinsically safe version as well as in an intrinsically safe version
for use with the most stringent requirements.
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Function
Features
• Transmitter in four-wire system with HART interface
• Housing can be mounted on 35 mm rail or 32 mm G rail
• Screw plug connector
• All circuits electrically isolated
• Output signal: 0/4 to 20 mA or 0/2 to 10 V
• Power supplies: 115/230 V AC/DC or 24 V AC/DC
• Explosion protection [EEx ia] or [EEx ib] for measurements
with sensors in the hazardous area
• Temperature-linear characteristic for all temperature sensors
• Temperature-linear characteristic can be selected for all tem-
perature sensors
• Automatic correction of zero and span
• Monitoring of sensor and cable for open-circuit and short-cir-
cuit
• Sensor fault and/or limit can be output via an optional sensor
fault/limit monitor
• Hardware write protection for HART communication
• Diagnostic functions
• Slave pointer functions
Mode of operation
The signal output by a resistance-based sensor (two-wire, three-
wire, four-wire system), voltage source, current source or ther-
mocouple is converted by the analog-to-digital converter
(1, function diagram) into a digital signal. This is evaluated in the
microcontroller (2), corrected according to the sensor character-
istic, and converted by the digital-to-analog converter (6) into an
output current (0/4 to 20 mA) or output voltage (0/2 to 10 V). The
sensor characteristics as well as the electronics data and the
data for the transmitter parameters are stored in the non-volatile
memory (3).
AC or DC voltages can be used as the power supply (13). Any
terminal connections are possible for the power supply as a re-
sult of the bridge rectifier in the power supply unit. The PE con-
ductor is required for safety reasons.
A HART modem or a HART communicator permit parameteriza-
tion of the transmitter using a protocol according to the HART
specification. The transmitter can be directly parameterized at
the point of measurement via the HART output terminals (10).
The operation indicator (4) identifies a fault-free or faulty operat-
ing state of the transmitter. The limit monitor (9) enables the sig-
naling of sensor faults and/or limit violations. In the case of a cur-
rent output, the current can be checked on a meter connected
to test socket (12).
Diagnosis and simulation functions
The SITRANS TW comes with extensive diagnosis and simula-
tion functions.
Physical values can be defined with the simulation function. It is
thus possible to check the complete signal path from the sensor
input to Inside the control system without additional equipment.
The slave pointer functions are used to record the minimum and
maximum of the plant’s process variable.
HART modem/
communicator
Current test
0/4 ... 20 mA
Output
U or I
Power
sup-
ply
unit
EEPROM
7
3
13
U
H
A
D
6
5
µC
A
12
11
10
A
D
RTD
TC
1
2
9
4
8
© Siemens AG 2009
