Weighing Electronics SIWAREX WT241 – Siemens

SIWAREX WP241 is a versatile and flexible weighing module that can be operated as a belt scale.
The electronic weighing system can be used in SIMATIC S7-1200 and uses all features of a modern automation system, such as integrated communication, operation and monitoring, the diagnostic system as well as the configuration tools in the TIA Portal.
Stand-alone mode without CPU is possible in addition.

Overview

SIWAREX WP241 is a flexible weighing module for belt scales. The compact module is easy to install in the SIMATIC S7-1200 automation system. It can also be operated as a standalone module, i.e. without a SIMATIC CPU.

Application

SIWAREX WP241 is the optimal solution wherever belt scales are used that demand high accuracy, high user-friendliness, and flexible system integration. The typical applications of the SIWAREX WP241 are determining the current material flow rate, belt load and belt speed. Furthermore, 6 totalizers are available for evaluating the amount of material conveyed.

System integration in SIMATIC

The electronic weighing system described here is a technology module for SIMATIC S7- 1200. It allows the user to configure all aspects of the automation solution, and weighing application, to his requirements. You can create optimal solutions for small and mediumsized plants by combining the suitable SIMATIC modules. You can create customized or industry-specific solutions in no time with the help of the configuration package available under the “Ready for use” application for SIMATIC.

Design

SIWAREX WP241 is a compact technology module in the SIMATIC S7-1200, and it allows direct connection to S7-1200 components via a sliding connector. Thanks to standard rail mounting, the installation and wiring outlay for the 70 mm-wide (2.76 inch) weighing module are very low.
The power supply, load cells, RS 485, digital input/outputs, and analog output are connected via the screw connector of the weighing module. An RJ45 connector is used for the Ethernet connection.

Benefits

SIWAREX WP241 offers the following key advantages:

  • Uniform design technology and consistent communication in SIMATIC S7-1200
  • Uniform configuration with TIA Portal
  • Operation without SIMATIC CPU possible
  • Direct connection of an operator panel via Ethernet
  • Four digital inputs and outputs, one analog output
  • Measurement of weight with a high resolution of ±4 million parts
  • Simple adjustment of belt scales using the SIWATOOL V7 program via the Ethernet interface – even without knowledge of SIMATIC
  • Replacement of module possible without renewed calibration of the scale
  • Use in hazardous area zone 2
  • Different calibration methods: With test weights, test chain, automatically or via material batch.
  • Specification of belt inclination angle
  • 6 totalization memories
  • Simulation of speed and belt load for test purposes
  • Comprehensive diagnostics functions

Design

SIWAREX WP241 is a compact technology module in the SIMATIC S7-1200, and it allows direct connection to S7-1200 components via a sliding connector. Thanks to standard rail mounting, the installation and wiring outlay for the 70 mm-wide (2.76 inch) weighing module are very low.
The power supply, load cells, RS 485, digital input/outputs, and analog output are connected via the screw connector of the weighing module. An RJ45 connector is used for the Ethernet connection.

Function

The primary task of the SIWAREX WP241 is to measure the speed of the belt, to measure and convert the sensor voltage to a weight value, and to precisely calculate the amount of material conveyed or material flow rate.
The volume of material conveyed can be recorded in 6 totalization memories: The accumulated totalization memory determines the conveyed material over the entire operating time of the scale (can only be reset by loading the factory settings). The overall total and the four remaining totalization memories are available for use as required. e.g. for recording the daily or weekly totals.
Four different options are available for rapid commissioning:

  • Automatic calibration
    The calibration is calculated automatically using the load cell parameters entered. Only the zero point has to be calculated on the actual plant.
  • Calibration with calibration weights or test weights
    Test weights are secured to the weighing equipment and the conveyor belt is started. The calibration values are calculated while the belt is running. The zero point must also be calculated.
  • Calibration with test chain
    Instead of test weights, a chain of a known weight can be placed on the measuring points of the belt. The calibration values are calculated as for calibration with test weights.
  • Calibration via material test
    This method can be used if a volume of material is available, but neither test weights nor a chain are available. The material can either be preweighed or weighed afterwards. The material is passed over the belt scale, and the weighing module calculates the calibration characteristic automatically.

Software

There is also the option of using a Windows PC for commissioning and servicing. The program SIWATOOL enables the belt scales to be set without prior knowledge of the automation system, as required. During servicing, the technician can use a PC to quickly and simply analyze and test the procedures in the scale.
The following are just some of the tasks that can be carried out using SIWATOOL V7:

  • Parameterization and calibration of the scale
  • Testing/Simulation of scale properties
  • Recording, analysis and export of scale traces (“Trace”)
  • Creation of backup files for rapidly replacing modules without calibration

SIWAREX WP241 SIWATOOL

It is also extremely helpful to analyze the diagnostics buffer which can be saved together with the parameters following reading out from the module.
Trace mode is provided to optimize the weighing sequences in the SIWAREX WP241 weighing module. The recorded weight values and associated states can be displayed as trends using SIWATOOL V7 and MS Excel.

Upgrading firmware

An additional program function can be used to download a new firmware version onto the SIWAREX WP241 on site. This means that firmware upgrades can be carried out on site as required anywhere in the world.

Technical specifications

SIWAREX WP241

Integration in automation systems

S7-1200

SIMATIC S7-1200 system bus

Operator panel and/or automation systems from other vendors

Via Ethernet (Modbus TCP/IP) or
RS 485 (Modbus RTU)

Communication interfaces

  • SIMATIC S7-1200 backplane bus
  • RS 485 (Modbus RTU)
  • Ethernet (SIWATOOL V7, Modbus TCP/IP)
  • Analog output 0/4 – 20 mA
  • 4 x digital outputs, 24 V DC floating, short-circuit proof
  • 4 x digital outputs, 24 V DC, floating

Commissioning options

  • Using SIWATOOL V7
  • Using function block in SIMATIC S7-1200 CPU / Touch Panel
  • Using Modbus TCP/IP
  • Using Modbus RTU

Measuring accuracy

Error limit according to DIN 1319-1 of full-scale value at 20 °C ± 10 K (68 °F ± 10 K)

0.05%

Internal resolution

up to ±4 million parts

Measuring frequency

100 / 120 Hz

Digital filter

Separate, variable adjustable low-pass and average filter for loading and speed

Filter for conveyor load

Low-pass filter (limit frequency 0.05 … 50 Hz)

Filter for belt speed

Low-pass filter (limit frequency 0.05 … 50 Hz)

Weighing functions

Readout data

  • Weight
  • Belt load
  • Material flow rate
  • Accumulated total
  • Main total
  • Free totals 1 … 4
  • Belt speed

Limits (min/max)

  • Belt load
  • Material flow rate
  • Belt speed

Load cells

Full-bridge strain gauges in 4-wire or 6-wire system

Load cell excitation

Supply voltage (regulated via feedback)

4.85 V DC

Permissible load resistance

  • RLmin

> 40 Ω

  • RLmax

< 4100 Ω

With SIWAREX IS Ex interface

  • RLmin

> 50 Ω

  • RLmax

< 4100 Ω

Load cell characteristic

1 … 4 mV/V

Permissible measurement signal range

-21.3 … +21.3 mV

Max. distance of load cells

500 m (229.66 ft)

Connection to load cells in Ex zone 1

Optionally via SIWAREX IS Ex interface (compatibility of the load cells must be checked)

Approvals/certificates

  • ATEX Zone 2
  • UL
  • EAC
  • KCC
  • RCM

Auxiliary power supply

Rated voltage

24 V DC

Max. power consumption

200 mA

Max. power consumption SIMATIC Bus

3 mA

IP degree of protection to DIN EN 60529; IEC 60529

IP20

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

  • Vertical installation

-10 … +40 °C (14 … 104 °F)

  • Horizontal installation

-10 … +55 °C (14 … 131 °F)

EMC requirements

according to EN 45501

Dimensions

70 x 75 x 100 mm (2.76 x 2.95 x 3.94 in)

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