Operating Principle - Siemens SITRANS TK-L 7NG3120-0 Betriebsanleitung

7NG3120-0, 7NG3122-0
1.3

Operating principle

The measured signal supplied by a resistance thermometer Pt100 (2, 3 or 4-wire
connection) is amplified in the input stage. The voltage, which is proportional to the
input quantity, is then converted to digital signals in an analog/digital converter ¡.
In the microprocessor © they are converted in accordance with the sensor charac-
teristic and further parameters (measuring range, attenuation and line resistance
etc.).
The signal prepared in this way is converted in a digital/analog converter ¢ to an
impressed direct current of 4 to 20 mA. The auxiliary power £ source is located in
the output signal circuit.
Sensor
Pt100
¡
I
Analog/digital converter
¡
Microcontroller
©
Digital/analog converter
¢
Auxiliary power source
£
Figure 1 Block diagram: operating principle of the SITRANS TK-L
24
SITRANS TK-L
©
μP
#
Operating instructions
Auxiliary power
£
¢
#
I
Load
SITRANS TK-L
A5E00095604-01