SIEMENS S7-300 SIPLUS SIWAREX U – a flexible weighing moduleHello

SIPLUS SIWAREX U electronic weighing systemSIPLUS SIWAREX U

SIPLUS SIWAREX U is a flexible weighing module for all simple weighing and force measuring tasks. The compact module can be integrated into SIPLUS automation systems without any problems.


SIPLUS extreme products are based on SIMATIC standard products. The contents listed here were taken from the respective standard products. SIPLUS extreme-specific information was added.

SIPLUS SIWAREX U electronic weighing system

Article No.

6AG1 950-2AA01-4AA0

Article No. based on

7MH4 950-2AA01

Range of ambient temperature

0 … +60 °C

Conformal coating

Coating of the printed circuit boards and the electronic components

Technical data

The technical data of the standard product applies except for the ambient conditions.

Ambient conditions

Relative humidity

100%, condensation/frost permissible. No commissioning in bedewed state.


SIPLUS SIWAREX U impresses customers with its clear benefits:

  • Uniform design and system-wide communication in SIMATIC
  • Implementation in a distributed system concept thanks to connection to PROFIBUS DB/PROFINET via ET 200M
  • Measuring of weight or force with a high resolution of 65000 parts and an accuracy of 0.05 %
  • Space savings by using the 2-channel version for two scales
  • Direct connection of a remote display to the TTY interface
  • Easy adjustment of the scales with the SIWATOOL U program
  • Theoretical calibration is possible without the need for calibration weights
  • Replacement of the module is possible without recalibrating the scales
  • Can also be used for Ex applications

SIPLUS SIWAREX U is the ideal solution wherever measurements are taken using strain-gage sensors such as load cells, force sensors or torque metering shafts. Typical applications of SIPLUS SIWAREX U are:

  • Fill-level monitoring of silos and hoppers
  • Monitoring of loads on cranes and cables
  • Measuring the loading on conveyor belts
  • Overload protection of industrial elevators or rolling mills
  • Balances in hazardous areas (using an Ex interface)
  • Monitoring of belt tension

SIPLUS SIWAREX U is a compact function module (FM) of SIMATIC S7-300 which can be directly snapped onto the SIMATIC S7-300 or ET 200M backplane bus. The installation/cabling work is considerably simplified by the snap-on system for DIN rails.

The load cells, power supply and serial interfaces are connected via the 20-pin standard front connector.

Operation of SIWAREX U in SIMATIC ensures that the weighing system is completely integrated into the automation system.

Technical specifications

SIPLUS SIWAREX U electronic weighing system

Integration in automation systems:


direct integration

S7-400 (H)

via ET 200M

PCS 7 (H)

via ET 200M


via IM or ET 200M

Automation systems from other manufacturers

via ET 200M

Stand-alone (without SIMATIC CPU)

possible with IM 153-1

Communication interfaces

  • SIMATIC S7 (I/O bus)
  • RS 232
  • TTY

Connection of remote indicator
(via serial TTY interface)

Total Channel 1, 2 or preset value 1, 2

Adjustment of weighing system

via SIMATIC (I/O bus) or PC with SIWATOOL U (RS 232)

Measurement properties

Error limit according to DIN 1319-1 of full-scale value at 20 °C ± 10 K

0,05 %

Internal ADC resolution
Data format of weight values

2 bytes (fixed point)

Number of measurements/second


Digital filter

0.05 to 5 Hz (in 7 steps), mean value filter

Weighing system functions

Weight values


Limit values

2 (min./max.)

Zero setting function

per command

Load cells

DMS in 4-wire or 6-wire system

Load cell supply

Infeed voltage Us (rated value)

6 V DC1)

Max. supply current

≤ 150 mA per channel

Permissible load resistance

  • RLmin

> 40 Ω per channel

  • RLmax

< 4010 Ω

with Ex(i) interface:

  • RLmin

> 87 Ω per channel

  • RLmax

< 4010 Ω

Permissible load cell characteristic value

up to 4 mV/V

Max. distance for load cells

500 m1)
150/500 m for Gas Group IIC

500 m1) for Gas Group IIB (see Equipment Manual SIWAREX IS)

Intrinsically safe weighing system infeed

optional (Ex interface) with SIWAREX IS

Power supply

Rated voltage

24 VDC

Max. current consumption

150 mA (single-channel) / 240 mA (two-channel)

Current consumption on backplane bus

≤ 100 mA


ATEX 95, FM, cULUS Haz. Loc.

IP degree of protection to DIN EN 60529; IEC 60529


Climatic requirements

Tmin (IND) to Tmax (IND) (operating temperature)

  • Vertical installation

0 … +60 °C

  • Horizontal installation

0 … +40 °C

EMC requirements to

NAMUR NE21, Part 1

EN 61326


40 x 125 x 130 mm

SIPLUS SIWAREX U is available with either one or two measurement channels. One measurement channel is required for each scales.

The primary task of SIWAREX U involves measuring the sensor voltage and converting this measurement to a weight value. The signal can be digitally filtered if required.

Apart from determining the weight, SIWAREX U also monitors two freely parameterizable limit values per measurement channel (min. or max.).

SIWAREX U is calibrated at the factory. This ensures both that theoretical calibration of the scales is possible without the need for calibration weights, and that modules can be replaced without the need for recalibrating the scales. In combination with “active bus modules”, modules can be replaced during normal operation.

Uniform, integrated communication between all system components supports quick, reliable and low-cost integration and diagnostics in process plants.

SIWAREX U has two serial interfaces. The TTY interface is used to connect up to four digital remote displays. In addition to the two weight values for weighing channels 1 and 2, two further values that can be set by the SIMATIC can also be indicated on the remote displays.

A PC can be connected to the RS232 interface for adjusting the scales.

SIWAREX U can not only be integrated into the system software via the classical PLC programming languages STL (Statement List), LAD (Ladder Diagram), FBD (Function Block Diagram) or SCL (Structured Control Language). Graphical configuration in CFC is also possible (CFC = Continuous Function Chart). Appropriate faceplates are available in PCS 7 for visualizing the scales.

In contrast to electronic weighing systems connected in series, with SIWAREX U there is no need for expensive add-on modules for connecting to SIMATIC.

Integration into SIMATIC results in freely programmable, modular weighing systems that can be adapted to internal company requirements as desired.

Using the SIWATOOL U software, the SIWAREX weighing modules can be set up with the convenience of Windows independently of the automation system. All the basic settings for the weighing modules can be specified in input screens, saved and printed out for the plant documentation.

A fast error search is assured in online mode thanks to the wide-ranging diagnostic functions of SIWATOOL U.

The SIWAREX U weighing module can also be used for hazardous areas (Zone 2). An intrinsically safe infeed can be implemented for the load cells through an optional Ex interface.