SIEMENS SITRANS P MPS series 7MF1570

SITRANS P MPS Design

SITRANS P MPS series 7MF1570

The transmitter has a flush-mounted piezo-resistive sensor with stainless steel diaphragm.

The transmitter is equipped with an electronic circuit fitted together with the sensor in a stainless steel housing. the cable also contains a strength cord and vent pipe.

The diaphragm is protected against external influences by a protective cap.

The sensor, electronic circuit and cable are sealed in a common housing of small dimensions.

The transmitter is temperature-compensated for a wide temperature range.

7MF1570 transmitter Application

The 7MF1570 transmitter is used for hydrostatic measurement of liquid levels, e.g. in water supply, ship installations, in the oil and gas industry etc. The transmitter measures the hydrostatic pressure (p = ρ * g * h, with ρ – density of the liquid, g – acceleration due to gravity, h – height of the liquid column).

The chemical stability of sensor, housing, o-ring and connection cable with the material should be monitored.

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 temperature 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.

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).

transmitter 7MF1570 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.

transmitter 7MF 1570 Connecting cables

The transmitter 7MF 1570 for measuring liquid levels (degree of protection IP68 according to DIN EN 60 529) is connected to the junction box 7MF 1570-8AA (IP54).

The transmitter cable is connected to the terminals 1 (-), 2 (+) and earth (Figure 4).

The strength cord is clamped between the two screws in the fixture. The vent pipe must be inside the junction box in connection with the atmosphere.

The feed voltage of the transmitter may be within the range from 10 to 36 V DC. The
resistance value for the maximum load depends on the voltage UB. It is determined
by the following equation:

Calibration

The transmitter has been calibrated to the measuring range at the factory and cannot
be re-calibrated.

Maintenance

The transmitter requires no maintenance.
The following points should be noted particularly when using the device:
• The maximum permissible pressure pmax of the transmitter may not be exceeded.
• The temperature of the medium in contact with the transmitter may not exceed
80°C.
• Avoid formation of ice on the process input of the transmitter because this could
damage the diaphragm.
• Prevent soiling of the sensor input.
• Avoid obstruction to the vent pipe in the special cable (influences the measuring
accuracy).