SIWAREX WP251 electronic weighing system

SIWAREX WP251 is a flexible weighing module for dosing and filling processes. The compact module can be installed seamlessly in the SIMATIC S7-1200 automation system. It can also be used without a SIMATIC CPU in stand-alone mode.

SIWAREX WP251 offers the following key advantages:

• Uniform design technology and consistent communication in SIMATIC S7-1200
• Uniform configuration with TIA Portal
• Operation without SIMATIC CPU also possible
• Direct connection of an operator panel possible via Ethernet
• Direct connection of a remote display via RS 485 interface
• Modbus TCP/IP interface
• Modbus RTU interface
• Four digital inputs and outputs, one analog output
• Measurement of weight and force with a high resolution of up to ± 4 million parts and an accuracy of 0.05%
• Simple calibration and setup of the scale using SIWATOOL V7 via the Ethernet interface
• Recovery-point for the simple restoration of all parameters
• Automatic calibration without the need for calibration weights
• Supports replacement of module without recalibration of scales
• Direct use in hazardous area zone 2

SIWAREX WP251 is the optimum solution wherever fast and precise dosing and filling are required. The typical applications of SIWAREX WP251 are:

• Automatic catchweighing instrument

• Automatic gravimetric filling instrument

• Non-automatic weighing instrument (NAWI)

SIWAREX WP251 is a compact technology module in the SIMATIC S7-1200, and communicates directly via the system bus with the SIMATIC S7-1200 controller.

The compact weighing module with a width of 70 mm (2.76 inches) is installed using a mounting rail. This is extremely user-friendly.

The connections for the power supply, the load cells, the RS-485 port, the digital inputs/outputs, and the analog output are located on removable screw connector blocks. An RJ45 port is available for the Ethernet connection (SIWATOOL and Modbus TCP/IP).

SIWAREX WP251 controls dosing and filling processes completely autonomously. The dosing valves (coarse/fine flow) can be controlled directly via the four digital outputs of the module. This achieves maximum accuracy since the weighing process is controlled completely independently of the CPU and its cycle time.

The CPU can be used to manage recipes and material parameters. These parameters and the desired setpoint are then transferred to SIWAREX WP251 by function block, and the dosing process is started. SIWAREX WP251 automatically optimizes the shut-off points, generates statistics, and logs every dosing task in the internal protocol memory that is also accessible from the CPU and can be read out by the CPU.

Diverse options are available for commissioning. The SIWAREX WP251 function block enables full access to all parameters of the SIWAREX WP251. The downloadable example application "ready-for-use" provides full data access to the weighing module, calibration options and operation of the scale - without any additional programming effort. Further, the PC service software SIWATOOL V7 that communicates via Ethernet with the SIWAREX module can be used for commissioning. Access using W-LAN is thus also possible by means of a WIFI access point. Consequently, remote access via the Internet is also no problem. For servicing purposes, centralized access to all scales from a single location is possible – worldwide. In addition, there is full access to all parameters and commands, both via the RS485 port (Modbus RTU) and via the Ethernet interface (Modbus TCP/IP), meaning that full commissioning and operation can also take place via these channels.

Weighing functions

SIWAREX WP251 provides the weighing modes Non-automatic weighing instrument, Automatic catchweighing instrument and Automatic gavimetric filling instrument.

In the operating modes Non-automatic weighing instrument and Automatic catchweighing instrument, there is a choice between filling mode and emptying mode. The entire filling or dosing process is controlled fully from SIWAREX WP251. It is only necessary to transfer a setpoint and a start command to the module. The coarse flow, fine flow and empty signals can be switched directly via the digital outputs of the module.

The weight, as well as all scale and dosing status bits, is available cyclically in the program code in the PLC for further evaluation. If stand-alone mode of the module is activated, there is an additional guarantee that dosing and operation of the scales can continue even in the event of a CPU stop.

Software

SIWATOOL V7 is a special program for commissioning and servicing and runs with Windows operating systems.
The program enables the user to perform scale calibration without requiring automation engineering skills. During servicing, the technician can use a PC to analyze and test the procedures in the scale. Reading the diagnostics buffer from SIWAREX WP251 is extremely helpful when analyzing events.

The following are just some of the tasks that can be carried out using SIWATOOL V7:

• Parameter assignment and calibration of the scale
• Testing of scale properties
• Recording and analysis of weighing sequence

Software SIWATOOL V7, layout of the program window

It is also extremely helpful to analyze the diagnostics buffer which can be saved together with the parameters from the module in a backup file.
Trace mode is provided to optimize the weighing sequences in the SIWAREX WP251 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 WP251 on site. This means that firmware upgrades can be carried out on site as required anywhere in the world.

Integration into the automation environment

SIWAREX WP251 is part of the SIMATIC S7-1200 basic controller range, and is integrated seamlessly into the TIA Portal. The free function block enables full access to all parameters, actual values, setpoints, weight values and status information (e.g. limits, coarse flow signal, fine flow signal, empty signal) conveniently and without programming effort. Customized operator interfaces can thus be created in conjunction with SIMATIC HMI touch panels. Management of several languages can also be easily implemented and organized.

The example project "Ready-for-use SIWAREX WP251" is available free of charge to help you to get started quickly and simply. This TIA portal project contains both the function block and a fully fledged visualization system for commissioning, operating and monitoring the SIWAREX WP251. The visualization can be freely edited and adapted, or transferred completely into an existing HMI project.

Stand-alone mode

Alternatively, SIWAREX WP251 can also be used without a SIMATIC CPU. In this case, the module is connected with a supply voltage of 24 V DC only. In this case, a PC (e.g. using an OPC server) or a Modbus-enabled operator panel can be used for operator input. Both Modbus interfaces of SIWAREX WP251 (TCP/IP and RTU) enable access to all parameters, actual values, setpoints, weight values and status information. A customized and plant-specific operator interface can thus be created on the PC or the Modbus-enabled operator panel. Integration into third-party systems is also no problem via the Modbus interfaces.