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4.4.2
How the electronics work
Description
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①
Measuring cell sensor
⑧
Buttons
②
Measuring amplifier
⑨
Display
③
Analog-to-digital converter
⑩
Connection for external ammeter
④
Microcontroller
⑪
EEPROM
⑤
Digital-to-analog converter
I
A
Output current
⑥
EEPROM
U
H
Auxiliary power
⑦
HART modem
Figure 4-6
How the electronics work
Function
● The input pressure is converted into an electrical signal by the sensor
①
.
● This signal is amplified by the measuring amplifier
②
and digitized in an analog-to-digital
converter
③
.
● The digital signal is analyzed in a microcontroller
④
and corrected with regard to linearity
and thermal characteristics.
● The digital signal is then converted in a digital-to-analog converter
⑤
into the output current
of 4 to 20 mA.
A diode circuit provides reverse polarity protection.
Description
4.4 Functional principle
SITRANS P320/P420 (mA/HART)
Operating Instructions, 06/2018, A5E44852162-AA
29