Siemens sitrans tr300, Manual

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Description
3.4 Operating principle
SITRANS TR200/TR300
Operating Instructions, 06/2010, A5E01071992-03
15
3.4 Operating principle
The mode of operation of the transmitter is explained below, using the function block
diagram.
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①
Sensor such as resistance thermometer, thermocouple, resistance-type transmitter, millivolt
transmitter
②
Analog-to-digital converter
③
Microcontroller, secondary side
④
Electrical 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 temporary connection of an amperemeter
Figure 3-2 SITRANS TR200/TR300 function block diagram
Mode of operation of transmitters
● The sensor
①
supplies an electrical signal
.
● 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 to
match the sensor characteristic curve.
● The signal is transferred across the electrical isolation
④
to the primary-side
microcontroller
⑤
.
● The analog output value is computed in the primary-side microcontroller
⑤
. The
functional status is indicated by LED
⑦
and the communications data prepared.
● Then the digital-to-analog converter
⑥
converts the signal into the output current of 4 to
20 mA.
● The auxiliary power supply source is located in the output signal circuit.