Siemens SITRANS P500, Руководство по эксплуатации, Страница: 26 / 238

Description
3.5 Functional principle
SITRANS P500 with HART
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Operating Instructions, 12/2014, A5E02344528-09
● The digital signal is analyzed in a microcontroller
④
and corrected with regard to linearity
and thermal characteristics.
● It is then converted in a digital-to-analog converter
⑤
to the output current of 4 to 20 mA.
A diode circuit provides reverse polarity protection.
● The measuring cell specific data, electronics data and parameterization data are saved in
two EEPROM
⑥
. One EEPROM is located in the measuring cell, the other is
incorporated in the electronics.
Operation
● Use the keys
⑧
to navigate and set different parameters.
● If your device has a display
⑨
, you can perform the parameter settings locally and track
messages from the device visually.
● Other settings can be implemented with a computer using a HART modem
⑦
.
3.5.2 Measuring cell operation
CAUTION
Toxic and hot media leaks
If the measured signal fails because of sensor breakage, the seal diaphragm and the
overload system may also be destroyed. In the worst case scenario of devices with a
destroyed seal diaphragm, the process medium leaks on the side ventilated with reference
pressure.
In case of sensor breakage, deactivate the lines to the device or depressurize the lines.
In the following sections, the process variable to be measured is called general inlet
pressure.
Overview
The following principles of operation are described:
● Differential pressure and flow rate
● Level
The following process connections are available, for example:
● ¼ - 18 NPT
● Flanged connection In accordance with EN 61518