How Th100 Works - Siemens SITRANS TH100 Operating Instructions Manual

4.1.3

How TH100 works

The following function block diagram clarifies the transmitter's mode of operation:
①
②
③
④
⑤
Figure 4-2
The signal delivered by an RTD Pt100 (two-wire, three-wire, four-wire system) is amplified in the
input stage. The voltage that is proportional to the input variable is then converted into digital
signals by a multiplexer in an analog-to-digital converter. These are converted in the
microcontroller in accordance with the sensor characteristic and further data, e.g. measuring
range or damping.
The signal prepared in this manner is then converted in a digital-to-analog converter into a load-
independent direct current of 4 to 20 mA.
The input and output circuits are each protected against electromagnetic interference through
the use of EMC filters.
SITRANS TH100/TH320/TH420/TR320/TR420/TF320/TF420 with 4 to 20 mA/HART
Operating Instructions, 05/2020, A5E41864807-AB
RTD Pt100
EM Input stage with protection compo‐
C_ nents
1
Ic Constant current source
MU Multiplexer
X
A/D Analog-to-digital converter
Function chart for SITRANS TH100
⑥
µC Microcontroller: Arithmetic func‐
tions and saving of all parameters
⑦
D/A Digital-to-analog converter
⑧
Power supply (U )/ output current (I
aux
⑨
EMC Output stage with protection compo‐
_2 nents
⑩
U Voltage converter, current converter,
ref
constant voltage source, and refer‐
ence voltage source
Description
4.1 SITRANS TH100
out
)
out
33