Description
3.4 How It works
SITRANS TH200/TH300
Operating Instructions, 06/2010, A5E00393069-03
15
3.4
How It works
Based on the function block diagram, the mode of operation is described below.
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①
Sensors such as the resistance thermometer, thermocouple, resistance-type transmitter,
millivolt transmitter
②
Analog-to-digital converter
③
Microcontroller secondary side
④
Galvanic isolation
⑤
Microcontroller primary side
⑥
Digital-to-analog converter
⑦
LED
U
aux
Auxiliary power supply
I
out
Output current
Test
Test terminals for brief connection of an ammeter
Figure 3-2
Function block diagram for SITRANS TH200/TH300
How the transmitter works
● The sensor supplies an electrical signal
①
.
● This signal is converted to a digital signal in an analog-to-digital converter
②
.
● The digital signal is evaluated in a secondary-side microcontroller
③
and corrected in
accordance with the sensor characteristic.
● The digital signal is transferred to the primary-side microcontroller
⑤
via the galvanic
isolation
④
.
● The analog output valve is calculated in the primary-side microcontroller
⑤
. The
functional status is indicated by LED
⑦
, and the communications data are prepared.
● The digital-to-analog converter
⑥
then converts the signal into an output current of 4 to
20 mA.
● The source of auxiliary power supply is located in the output signal circuit.
Summary of Contents for SITRANS T4200
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