Siemens sitrans tr200, Operating Instructions Manual

Page: 15 / 78

Description
3.4 Operating principle
SITRANS TR200/TR300
Operating Instructions, 04/2007, A5E01071992-01
15
3.4 Operating principle
The mode of operation of the transmitter is explained below, using the function block
diagram.
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Figure 3-5 SITRANS TR200/TR300 function block diagram
➀ 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 LEDs
U
aux
Auxiliary power supply
I
out
Output current
Test Test terminals for temporary connection of an amperemeter
Mode of operation of transmitters
● The sensor ➀ 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.