Siemens SITRANS P - Manual (Page 12)

SITRANS P measuring instruments for pressure
Transmitters for gage, absolute and differential pressure
SITRANS P250 for differential pressure
2/12 Siemens FI 01 · 2009
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Overview
SITRANS P250 transmitter for differential pressure
The SITRANS P250 transmitter measures the differential pres-
sure of liquids and gases.
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Benefits
• High measuring accuracy
• Sturdy stainless steel enclosure
• For aggressive and non-aggressive media
• For the measurement of the differential pressure of liquids and
gases
• Temperature-compensated measuring cell
• Compact design
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Application
The SITRANS P250 transmitter for differential pressure is prima-
rily used in the following industries:
• Chemical industry
• Pharmaceutical industry
• Food industry
• Mechanical engineering
• Shipbuilding
• Water supply
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Design
Main components:
• Stainless steel enclosure with piezo-resistive ceramic measur-
ing cell and (temperature-compensated) electronics module.
• Process connection made of stainless steel in diverse designs
(see Selection and ordering data)
• Electrical connection through connectors acc. to EN 175301-
803-A and round connectors M12, as well as with permanently
fixed cable
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Function
The pressure transmitter measures the differential pressure of
liquids and gases.
Mode of operation
SITRANS P250 pressure transmitter, function diagram
The piezo-resistive ceramic measuring cell (membrane) has a
Wheatstone bridge circuit, on which the operating pressure P1
and P2 of the media acts at both ends.
The voltage output from the measuring cell is converted by an
amplifier into an output current of 4 to 20 mA or an output voltage
of 0 to 5 or 10 V DC.
The output current and voltage are linearly proportional to the in-
put pressure.
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Technische Daten
SITRANS P250 differential pressure transmitter
Application
Differential pressure transmitter Liquids and neutral gases
Mode of operation
Measuring principle Piezo-resistive measuring cell
(ceramic diaphragm)
Input
Measured variable Differential pressure
Measuring range 0 ... 0.1 to 0 ... 25 bar
(0 ... 1.45 to 0 ... 363 psi)
Operating pressure ≤ 25 bar (363 psi) at a differential
pressure range < 6 bar (87 psi)
≤ 50 bar (725 psi) at a differential
pressure range > 10 bar (145 psi)
Burst pressure 1.5 x operating pressure
Output
Output signal
• Current output signal 4 ... 20 mA
• Voltage output signal 0 ... 5 V and 0 ... 10 V DC
Load
3-wire > 10 k Ω
2-wire ≤ (U
H
- 11 V) / 0.02 A
Measuring accuracy
Dynamic behavior (at 25°C (77°F),
including conformity error, hystere-
sis and repeatability) ≤ 1 % of typical full-scale value,
see "Measuring range" table
Long-term drift acc. to IEC 60770 ≤ 0.5 % of full-scale value/year
Influence of ambient temperature
• Start of scale ≤ 0.6 %/10 K of full-scale value
(
≤ 1.2 %/10 K for measuring cell
0 ... 0.1 bar (1.45 psi))
• Full-scale value ≤ 0.22 %/10 K of full-scale value
(
≤ 0.37 %/10 K for measuring cell
0 ... 0.1 bar (1.45 psi))
Dynamic behavior Suitable for static and dynamic
measurements
Response time T
99
< 5 ms
Load variation < 50 Hz
p
1
p
2
U
const.
U
I I
0
, U
B
© Siemens AG 2008