Connecting two SIWAREX MS weighing modules to an OWEN PLC100 is not an electrical-interface problem alone. The available evidence identifies the SIWAREX RS232 port as a parameterization connection for SIWATOOL MS and the TTY port as a connection for remote digital indicators. Neither description establishes a PLC data protocol that an RS485 converter can expose.
Identify Each SIWAREX MS Interface
| Interface | Evidence-supported purpose | Integration consequence |
|---|---|---|
| RS232 | Parameterizing the module with SIWATOOL MS and connecting a computer | Do not assume that converting its electrical layer to RS485 creates PLC process-data access. |
| TTY current loop | Connecting remote digital indicators | Confirm the message protocol before selecting a TTY/RS485 converter. |
| Controller-side bus | The module communicates with its intended controller through its bus | The PLC must support that bus and the required data exchange, or an intermediate controller must translate it. |
Why a Current-Loop Converter Is Insufficient
The same limitation applies to an RS232/RS485 converter: changing voltage levels and wiring does not translate addressing, framing, commands, or application data.
The evidence also contains conflicting, model-dependent bus suggestions—MPI or PROFIBUS are mentioned, while the module is described as intended for the S-200 controller line. Treat the exact controller bus as unresolved until the SIWAREX MS documentation and module order number confirm it.
Select a Viable Architecture
The supported fallback is to install the SIWAREX MS modules with the supplied Siemens CPU224, then exchange required values between that controller and the PLC100 over a mutually supported RS485 protocol. This adds a controller and translation logic, but it preserves the SIWAREX module's intended controller connection. The evidence does not specify the inter-controller protocol, so confirm it independently before implementation.
Using the Siemens controller for the complete application is another stated option.
Verification Procedure
- Read the exact SIWAREX MS order number and verify the documented purpose and protocol of its RS232, TTY, and controller-bus connections.
- Confirm whether the TTY output supplies only remote-indicator data or offers a documented command/response protocol accessible to another PLC.
- Verify that the PLC100, two SIWAREX modules, and IP320 panel can use distinct ports or compatible multidrop protocols; physical RS485 compatibility alone is not sufficient.
- If using the CPU224 gateway architecture, configure and test SIWAREX acquisition first, then map only the required weight and status data into the selected PLC100 communication protocol.
- Verify parameterization and calibration through SIWATOOL MS. For CPU224 programming, the evidence identifies MicroWin and a PPI cable, but it does not confirm that a generic USB/RS485 or RS232/RS485 converter can replace the required programming interface.
FAQ
Can SIWAREX MS TTY be converted directly to RS485?
A converter can change the electrical interface, but the evidence identifies TTY as a remote-indicator connection and does not establish a PLC-compatible protocol.
Will an RS232-to-RS485 converter connect SIWAREX MS to PLC100?
Not by itself. The SIWAREX RS232 port is identified for SIWATOOL MS parameterization and computer connection; converting it to RS485 does not translate the application protocol.
How can two SIWAREX MS modules exchange data with PLC100?
Use the supplied CPU224 to operate the SIWAREX modules, then exchange selected weight and status values with the PLC100 through a mutually supported RS485 protocol. Confirm that protocol and the required register mapping before selecting converters.