Mode Of Operation; Installation - Siemens SITRANS P Série Mode D'emploi

Operating Instructions
3

Mode of operation

The pressure of the medium acts on the stainless steel diaphragm which is deflected
to transmit the pressure to the piezo-resistive bridge in the measuring sensor. Every
sensor is compensated for changes in temperature and operates within a wide tem-
perature range.
The output voltage signal of the sensor is fed to an electronic circuit which converts
it into an output current in the range from 4 to 20 mA. The hydrostatic pressure which
is proportional to the submersion depth acts on the diaphragm of the sensor. This
pressure is compared with the atmospheric pressure which acts on the other side of
the sensor by means of the vent pipe in the connecting cable. The cable screen is
connected to the housing.
Diaphragm
p
Figure 2
The transmitter is supplied from a 10 V to 36 V DC source. Protective diodes at the
input protect against reverse polarity or overvoltage. The transmitter complies with
the regulations DIN EN 61 326 and NAMUR NE 21 regarding the electromagnetic
compatibility (EMC).
4

Installation

The transmitter 7MF1570 is installed hanging downwards on the cable. In moving
media, the transmitter must be fixed to prevent measuring errors. This can be done
with a guide tube or an additional weight on the transmitter (max. tensile force on the
strength cord of the connecting cable = 300 N).
The cable should be fixed above the vessel with the provided cable hanger
7MF1570-8AB and to connect the cable itself to the also provided junction box
7MF1570-8AA. The junction box must be mounted in the proximity of the measuring
point in a position compatible with its degree of protection (IP66).
Make sure that the inlet openings on the protective cap of the transmitter are not
soiled in order to guarantee perfect functioning.
NOTE
The medium may not freeze.
20
Sensor
const.
Transmitter 7MF1570, block diagram
U
U
EM
I
+2 (brown)
I , U
o B
-1 (blue)
Vent pipe
Screen
SITRANS P, MPS Series
A5E00136035-04