Siemens P technical specifications Function diagram of the electronics

© Siemens AG 2008

SITRANS P measuring instruments for pressure

Transmitters for gage, absolute and differential pressure, flow and level

■Function

Operation of the electronics with PROFIBUS PA communica-

DS III, DS III PA and DS III FF series

Technical description

Operation of the electronics with PROFIBUS PA communica- tion

tion

	8		9
			0 0 0 0 0
			0 0
			10
2	3	4	5

mC	IA, UH
7
HART interface

EEPROM 6

Electronics

1	6
Sensor	EEPROM
P

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

mC	PA
	interface

EEPROM 6

Electronics

1	6
Sensor	EEPROM
pe	Measuring cell

2

	Power supply
-PA		10
PROFIBUS	Power	PROFIBUS-DP
	supply
	unit
	Coup-
	ler
	11	Bus-
	12	Master

e Measuring cell

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 the electronics

The bridge output voltage created by the sensor (1, Figure "Function diagram of the electronics") is amplified by the instru- ment amplifier (2) and digitized in the analog-to-digital converter

(3). The digital information is evaluated in a microcontroller, its linearity and temperature response corrected, and converted in

adigital-to-analog converter (5) into an output current of 4 to 20 mA.

The diode circuit (10) protects against incorrect polarity.

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 3 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 HART modem (7) permits parameterization using a protocol according to the HART specification.

The pressure transmitters with spans ≤ 63 bar measure the input pressure compared to atmosphere, transmitters with spans

≥160 bar compared to vacuum.

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 the electronics

The bridge output voltage created by the sensor (1, Figure "Function diagram of the electronics") is amplified by the instru- ment amplifier (2) and digitized in the analog-to-digital converter

(3). The digital information is evaluated in the microcontroller, its linearity and temperature response corrected, and provided on the PROFIBUS PA through an electrically isolated PA 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 first memory is linked with the measuring cell, the sec- ond with the electronics. This modular design means that the electronics and the measuring cell can be replaced separately from one another.

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 PROFIBUS PA. Param- eterization data and error messages are transferred by acyclic data transmission. Special software such as SIMATIC PDM is re- quired for this.

Siemens FI 01 · 2009

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