Siemens P Design Function Device comprises, Operation of the electronics with Hart communication

	© Siemens AG 2008
	SITRANS P measuring instruments for pressure
	Transmitters for food, pharmaceuticals and biotechnology
			SITRANS P300 for gage and absolute pressure
■Design		■Function
The device comprises:			Operation of the electronics with HART communication
• Electronics

•Housing

•Measuring cell

	8		9
			0 0 0 0 0
			0 0
2	3	4	5

mC

7

HART interface

EEPROM 6

Electronics

1	6
Sensor	EEPROM
Pe	Measuring cell

2

10

IA, UH

Perspective view of the SITRANS P300

The housing has a screw-on cover (3), with or without an inspec- tion window depending on the version. The electrical terminal housing, the buttons for operation of the device and, depending on the version, the digital display are located under this cover. The connections for the auxiliary power UH and the shield are in the terminal housing. The cable gland is mounted on the side of the housing. The measuring cell with the process connection (5) is located on the underside of the housing. Depending on the version of the device, the measuring cell with the process con- nection may differ from the one shown in the diagram.

1Measuring cell sensor

2 Instrument amplifier

3 Analog-to-digital converter

4Microcontroller

5Digital-to-analog converter

6One non-volatile memory each in the measuring cell and electronics

7 HART interface

8 Three input keys (local operation)

9 Digital display

10 Diode circuit and connection for external ammeter

IA	Output current
UH	Power supply
Pe	Input variable

Function diagram of electronics

The input pressure is converted into an electrical signal by the sensor (1). This signal is amplified by the measuring amplifier (2) and digitalized in an analog to digital converter (3). The digital signal is analyzed in a microcontroller (4) and corrected with re- gard to linearity and thermal characteristics. In a digital to ana- log converter (5) it is then converted into the output current of 4 to 20 mA. A diode circuit provides reverse voltage protection. You can make an uninterrupted current measurement with a low- ohm ammeter at the connection (10). The data specific to the measuring cell, the electronic data and parameter settings are stored in two non-volatile memories (6). The first memory is linked with the measuring cell, the second with the electronics.

The buttons (8) can be used to call up individual functions, so- called modes. If you have a device with a digital display (9), you can use this to track mode settings and other messages. The ba- sic mode settings can be changed with a computer via the HART modem (7).

Siemens FI 01 · 2009

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