Mode Of Operation - Siemens SITRANS TH100 Operating Instructions Manual

3.4

Mode of operation

The following function block diagram clarifies the transmitter's mode of operation:
①
③
⑤
⑦
⑨
Figure 3-2
Mode of operation of the transmitter
The signal delivered by a Pt100 resistance thermometer (two-wire, three-wire, four-wire
system) is amplified in the input stage. The voltage 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
Operating Instructions, 06/2010, A5E00331168-02
Pt100 resistance thermometer
Constant current source
Analog-to-digital converter
Digital-to-analog converter
Output stage with protection components
Function block diagram SITRANS TH100
②
Input stage with protection components
④
Multiplexer
⑥
Microcontroller: arithmetic functions and
saving of all parameters
⑧
Auxiliary power supply (U
current (I )
out
⑩
Voltage converter, current converter,
constant voltage source, and reference
voltage source
Description
3.4 Mode of operation
out
)/ output
aux
13