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3.4
How It works
Based on the function block diagram, the mode of operation is described below.
①
②
③
④
⑤
⑥
⑦
U
aux
I
out
Test
Figure 3-2
How the transmitter works
● The sensor supplies an electrical signal
● This signal is converted to a digital signal in an analog-to-digital converter
● The digital signal is evaluated in a secondary-side microcontroller
● The digital signal is transferred to the primary-side microcontroller
● The analog output valve is calculated in the primary-side microcontroller
● The digital-to-analog converter
● The source of auxiliary power supply is located in the output signal circuit.
SITRANS TH200/TH300
Operating Instructions, 06/2010, A5E00393069-03
Sensors such as the resistance thermometer, thermocouple, resistance-type transmitter,
millivolt transmitter
Analog-to-digital converter
Microcontroller secondary side
Galvanic isolation
Microcontroller primary side
Digital-to-analog converter
LED
Auxiliary power supply
Output current
Test terminals for brief connection of an ammeter
Function block diagram for SITRANS TH200/TH300
accordance with the sensor characteristic.
④
isolation
.
functional status is indicated by LED
20 mA.
①
.
⑦
, and the communications data are prepared.
⑥
then converts the signal into an output current of 4 to
Description
3.4 How It works
②
.
③
and corrected in
⑤
via the galvanic
⑤
. The
15
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