Siemens Operation of the electronics with Profibus PA communica, Tion Electronics

© Siemens AG 2008

SITRANS P measuring instruments for pressure

Transmitters for food, pharmaceuticals and biotechnology

SITRANS P300 for gage and absolute pressure

Operation of the electronics with PROFIBUS PA communica-	Mode of operation of the FOUNDATION Fieldbus
tion	electronics

	8		9
			0 0 0 0 0
2	M
			0 0
2	3	4	5	7

	mC	PA
		interface
				Power supply
			-PA		10
			PROFIBUS	Power	SIBUPROF-DP
	EEPROM	6		supply
				unit
				Coup-
				ler
		Electronics		11
					Bus-
1	6
				12	Master
	EEPROM
Sensor
pe	Measuring cell

	8		9
			0 0 0 0 0
	M
			0 0
2	3	4	5	7

mC	FF
	interface

EEPROM 6

Electronics

1	6
Sensor	EEPROM
pe	Measuring cell

Power supply

10

Power supply unit

Coup-

ler

1	Measuring cell sensor	8	Three input keys
2	Instrument amplifier		(local operation)
3	Analog-to-digital converter	9	Digital display
4	Microcontroller	10	Power supply
5	Electrical isolation	11	DP/PA coupler or link
6	One non-volatile memory	12	Bus master
	each in the measuring cell	pe
7	and electronics		Input variable
	PROFIBUS-PA interface

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. It is then made available at the PROFIBUS PA over an electrically isolated PROFIBUS PA interface (7). 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 over the bus master (12).

1	Measuring cell sensor	8	Three input keys
2	Instrument amplifier		(local operation)
3	Analog-to-digital converter	9	Digital display
4	Microcontroller	10	Power supply
5	Electrical isolation	pe
6	One non-volatile memory		Input variable
	each in the measuring cell

and electronics

7FF interface

Function diagram of electronics

The bridge output voltage created by the sensor (1, Figure "Function diagram of electronics") is amplified by the instrument amplifier (2) and digitized in the analog-to-digital converter (3). The digital information is evaluated in the microcontroller, its lin- earity and temperature response corrected, and provided on the FOUNDATION Fieldbus through an electrically isolated FOUNDATION Fieldbus Interface (7).

The data specific to the measuring cell, the electronics data, and the parameter data are stored in the two non-volatile memories

(6). The one memory is coupled to the measuring cell, the other to the electronics. As the result of this modular design, the elec- tronics and the measuring cell can be replaced separately from each other.

Using the three input keys (8) you can parameterize the pressure transmitter directly at the point of measurement. The input keys can also be used to control the view of the results, the error mes- sages and the operating modes on the digital display (9).

The results with status values and diagnostic values are trans- ferred by cyclic data transmission on the FOUNDATION Fieldbus. Parameterization data and error messages are trans- ferred by acyclic data transmission. Special software such as National Instruments Configurator is required for this.

Mode of operation of the measuring cells

The process connections available include the following:

•G½

•½-14 NPT

•Front-flush diaphragm:

-Flanges to EN

-Flanges to ASME

-NuG and pharmaceutical connections

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Siemens FI 01 · 2009