Siemens Measuring cell for gage pressure with front-flush diaphragm, Parameterization

© Siemens AG 2008

SITRANS P measuring instruments for pressure

Transmitters for gage pressure for the paper industry

SITRANS P300 and DS III series

with PMC connection – Technical description

Mode of operation of the FOUNDATION Fieldbus electronics

Mode of operation of the measuring cell

8	9
	0 0 0 0 0
M
	0 0
2

Measuring cell for gage pressure with front-flush diaphragm

2 3 4 5 7

mC	FF
	interface

EEPROM 6

Electronics

1	6
Sensor	EEPROM

Power supply

10

Power supply unit

Coup-

ler

5

4

1

2

3 pe

1Measuring cell

2Process connection

3 Seal diaphragm

4 Filling liquid

5 Silicon pressure sensor

pe Pressure as input variable

pe Measuring cell

Measuring cell for gage pressure, with front-flush diaphragm, function diagram

The pressure pe is applied through the process connection

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.

(2, Figure "Measuring cell for gage pressure, with front-flush di- aphragm for paper industry, function diagram") to the measuring cell (1). This pressure is subsequently transmitted further through the seal diaphragm (3) and the filling liquid (4) to the sil- icon pressure sensor (5) whose measuring diaphragm is then flexed. This changes the resistance of the four piezo-resistors fit- ted in the diaphragm in a bridge circuit. This change in resis- tance results in a bridge output voltage proportional to the input pressure.

Parameterization

Depending on the version, there are a range of options for pa- rameterizing the pressure transmitter and for setting or scanning the parameters.

Parameterization using the input keys (local operation)

With the input keys you can easily set the most important param- eters without any additional equipment.

Parameterization using HART communication

Parameterization using HART communication is performed with a HART communicator or a PC.

		+
SITRANS P	230 ... 1100 W	Power supply
transmitter
	HART
	communicator

Communication between a HART communicator and a pressure transmitter

When parameterizing with the HART communicator, the connec- tion is made directly to the 2-wire system.

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Siemens FI 01 · 2009