The SIWAREX FTC (Flexible Technology for Continuous Weighing) is a versatile and flexible weighing module for conveyor scales, differential proportioning weighers and bulk flow meters. It can also be used to record weights and measure force. The SIWAREX FTC function module is integrated in SIMATIC S7/PCS7, and uses the features of this modern automation system, such as integral communication, diagnostics and configuration tools.

Product No. / Product Description SIWAREX FTC Ordering data

SIWAREX FTC is characterized by the following features:

  • Uniform design, and totally integrated communication in SIMATIC S7 and SIMATIC PCS 7
  • Uniform configuration with SIMATIC
  • Direct use in the SIMATIC automation system
  • Use in distributed plant concept through connection to PROFIBUS DP/PROFINET using ET 200M
  • Measurement of weight or force with high resolution of 16 million intervals
  • High accuracy 3 x 6 000 d
  • Use with analog strain-gage load cells of types SIWAREX R and SIWAREX WL200
  • Alternative option of connecting individual load cells from the manufacturers METTLER TOLEDO, WIPOTEC and PESA
  • Display with SIMATIC standard operator panels
  • Parameterizable inputs and outputs
  • Parameterizable for highly versatile applications
  • Flexible adaptation to different requirements with SIMATIC
  • Simple adjustment of scale using the SIWATOOL FTC program
  • Theoretical adjustment without adjustment weights
  • Replacement of module without renewed adjustment of scale
  • Recording of weighing sequence
  • 8 totalization memories with different digit intervals
  • Can be used in Ex applications

The SIWAREX FTC weighing module is the optimum solution wherever high demands are placed on continuous weighing procedures. Thanks to its outstanding measuring properties, weights can be measured with extreme accuracy in up to three ranges. In the case of force measurements, the value can be measured bidirectionally.

Typical applications for SIWAREX FTC include:

  • Flowrate/flow measurement
  • Volume measurement
  • Material loading, summation
  • Flowrate/flow control
  • Belt load measurement
  • Belt scale/weighfeeder
  • Loss-in-weight scale
  • Force measurement

SIWAREX FTC is a function module of SIMATIC S7-300 which can be directly snapped onto the SIMATIC S7‑300 or ET 200M backplane bus. Thanks to the snap-on mounting rail system, very little work is required to install/cable the 80 mm wide weighing module.

The load cells, the RS 485 serial interface, the analog output and the digital inputs and outputs are connected by means of the 40‑pin standard front connector, the PC (RS 232) by means of a 9‑pin SUB-D connector and the power supply by means of a separate 2-pin connector.

Operation of SIWAREX FTC in SIMATIC enables the weighing system to be completely integrated into the automation system.

Technical specifications


Use in automation systems


Directly or via ET 200M


Through ET 200M

S7-400 (H)

Through ET 200M

PCS 7 (H)

Through ET 200M

Communication interfaces


Through backplane bus

RS 232

For SIWATOOL or printer connection

RS 485

For remote display or digital load cell

Module parameterization


Using SIWATOOL FTC software (RS 232)

Measuring properties

Accuracy to EN 45501

3 x 6 000 d ≥ 0.5 μV/e

Internal resolution

+/- 8 million parts

Internal/external updating rate

400/100 Hz

Several parameterizable digital filters

Critically dampened, Bessel, Butterworth (0.05 … 20 Hz), mean-value filter

Weighing functions

  • Non-automatic weighing machine, force measurement
  • Conveyor scale
  • Differential proportioning weigher
  • Bulk flow meter

Load cells

Strain gages in 4-wire or 6-wire system

3 characteristic value ranges

1, 2 or 4 mV/V

Load cell powering

Supply voltage US (rated value)

10.3 V DC

Max. supply current

184 mA

Permissible load cell resistance

  • RLmin

> 56 Ω
> 87 Ω with Ex interface

  • RLmax

≤ 4 010 Ω

Max. distance of load cells

When using the recommended cable:


1 000 m (3 280 ft)

In hazardous area1)

  • For gases of group IIC

300 m (984 ft)

  • For gases of group IIB

1 000 m (3 280 ft)

Connection to load cells in Ex zone 1

Optionally via SIWAREX IS Ex interface

Ex approvals zone 2 and safety

ATEX 95, FM, cULUS Haz. Loc.

Auxiliary power supply

Rated voltage

24 V DC

Max. power consumption

500 mA

Current consumption from backplane bus

typ. 55 mA


Digital inputs

7, electrically isolated

Digital outputs

8, electrically isolated

Counter input

Up to 10 kHz

Analog output

  • Current range

0/4 … 20 mA

  • Updating rate

100 Hz

Degree of protection according to EN 60529; IEC 60529


Climatic requirements

Tmin (IND) … Tmax (IND) (operating temperature)

  • Horizontal installation

-10 … 60 °C (14 … 140 °F)

  • Vertical installation

-10 … 40 °C (14 … 104 °F)

EMC requirements

EN 61326, EN 45501, NAMUR NE21, Part 1


80 x 125 x 130 mm (3.15

 x 4.92 x 5.12 in)


600 g (0.44 lb)


The main tasks of SIWAREX FTC are the high-precision measurement of the current weight, and the exact calculation of the conveyed quantity or flow. In “Force measurement” mode, SIWAREX FTC measures the force bidirectionally.

The conveyed quantity can be recorded in 8 totalization memories. Through integration in SIMATIC it is also possible to directly control scale operation by means of a PLC program. This means that the tasks can be sensibly divided: The weighing functions are implemented in the SIWAREX FTC, the interlocking and logic functions for the plant control in the SIMATIC CPU.

Weighing functions

The following operating modes can be set:

Weight measurement and force measurement

In this operating mode, the weight value or the force is determined, processed in the PLC and then displayed.
For this purpose, the configuration package can be selected.

Conveyor scale / weighfeeder

The functions of a conveyor scale are implemented in this operating mode. Calculations are performed for the typical process values; belt load, flowrate and belt speed. Commands can be used to control the belt and display the required values. A weighfeeder can be implemented by activating the SIMATIC PID controller.

Scale faceplate of a conveyor scale

Differential proportioning weigher – Loss-in-weight

The functions of a differential proportioning weigher are implemented in this operating mode. The actual weight of the container is measured and the flowrate is regulated according to the preset setpoint.

Application-specific parameters, such as proportioning parameters, device and material characteristics, can be set directly in SIWAREX FTC. Various commands are available that have been fine-tuned to the requirements of the differential proportioning weigher, such as proportioning (manual, automatic, gravimetric, volumetric), filling and emptying.

The high measurement resolution, real-time signal processing, detection and filtering of signals in the weighing electronics enable extremely high proportioning accuracy.

Scale faceplate of a differential proportioning weigher

Bulk flow meter

The functions of a bulk flow meter are implemented in this operating mode. The calculations for the typical process values; flow and conveyed quantity, are performed in the SIWAREX module. Application-specific parameters for setting the scales and commands for their operation are also available.

View of a bulk flow meter

Monitoring and control of the load cell signals and statuses

The SIWAREX FTC weighing module monitors the statuses during the weighing process, and informs the operator of any irregularities. The optimized exchange of data within SIMATIC permits direct evaluation of the load cell signals in the PLC program.

Influencing of the weighing sequences by the PLC means that the SIWAREX FTC can be easily adapted to any modifications in system technology.

A module can be replaced without recalibrating the scales. When using “active bus modules”, replacement is also possible during operation.

Applications of SIWAREX FTC

Integration in SIMATIC

SIWAREX FTC is completely integrated into the SIMATIC S7 and SIMATIC PCS 7. Users can freely configure their automation solution – including the weighing application.

The right combination of SIMATIC components can produce optimum solutions for small, medium-size and large plants. The scales are operated and monitored using SIMATIC standard operator panels. Needless to say, these operator panels can also be simultaneously used for the operator control and monitoring of the plant.

Customized or sector-specific solutions can be developed extremely quickly using the configuration package and example applications for SIMATIC.

SIMATIC S7/PCS 7 configuration with SIWAREX FTC (medium-sized plants)


Adjustment of the scale using SIWATOOL FTC

SIWATOOL FTC is a special program for adjusting and servicing the scale and runs with Windows operating systems.

The program enables the scales to be commissioned without the need for prior knowledge of the automation system. When servicing, the technician can use a PC to analyze and test the procedures in the scale. Reading out the diagnostics buffer from the SIWAREX FTC is extremely helpful when analyzing events.

The following are just some of the tasks that can be carried out using SIWATOOL FTC:

  • Parameterization and adjustment of the scale
  • Testing of scale properties
  • Saving and printing scale data
  • Recording and analysis of weighing sequence

Settings in SIWAREX FTC software

It is also extremely helpful to analyze the diagnostics buffer which can be saved together with the parameters following reading out from the module.

The SIWAREX FTC weighing module includes a trace mode for checking of weighing sequences. The recorded weight values and associated statuses can be displayed as traces using SIWATOOL FTC and MS Excel.

Upgrading firmware

A further program function can be used to download a new firmware version onto the SIWAREX FTC on site. This means that firmware upgrades can be carried out on site as required anywhere in the world.

Reading out of weighing reports

The totalization memories can be saved on a MMC (Micro Memory Card) inserted into the SIWAREX FTC.

SIWAREX FTC – simple configuring

Integration in SIMATIC can result in freely-programmable, modular weighing systems for conveyor scales, bulk flow meters and differential proportioning weighers, which can be modified to meet operational requirements.

A free version of the ready-to-use SIWAREX FTC software “Getting started” is also available respectively for the conveyor scale, bulk flow meter and loss-in-weight feeder modes. It shows beginners how to integrate the module into a STEP 7 program and provides a basis for application programming. This allows you to implement the belt scale very easily with an operator panel connected directly to the SIMATIC CPU.

Scale faceplate in the SIWAREX FTC “Getting started” software