Enhance Your SCADA Performance with Modbus Gateways

The continued focus on energy efficiency increases the significance of supervising and managing the numerous power automation devices deployed at field sites using supervisory control and data acquisition (SCADA) systems.

Given that most of these devices, such as power meters, UPSs, smart relays, and ATS controllers, utilize Modbus RTU protocols due to their simplicity, compatibility can be a concern since SCADA systems typically utilize Ethernet-based protocols like Modbus TCP. In power monitoring scenarios, along with converting Modbus RTU/ASCII to Modbus TCP, the scale of device deployment also poses challenges for system integrators.

To address the interoperability issue, cost-effective gateways that efficiently convert between Modbus TCP and Modbus RTU are the ideal solution. Moreover, for managing large-scale device deployments, Modbus gateways featuring multiple serial ports (e.g., 8 or 16 ports) are the most suitable solution.

Eliminating Unnecessary Delays

In critical large-scale applications where every millisecond is crucial, SCADA systems cannot tolerate delays in receiving responses from field devices to simultaneous data requests. It is not uncommon for SCADA systems to encounter significant time gaps between reading the initial and last device because of the standard transparent mode communication in the Modbus gateway market, which handles simultaneous requests and responses sequentially. Reduced scan times will undoubtedly streamline operations and lighten the workload for system integrators.

The Elegance of Agent Mode

Creating a new system is a strategy to achieve reduced scan times. The pivotal element for a newly designed system’s success lies in a gateway that enhances SCADA system performance, boosts the flexibility of SCADA program designs, and simplifies configuration. Gateways supporting agent-mode communication with high multiport density can accomplish these objectives. Agent mode, developed to overcome the limitations of transparent mode, allows independent communication on each side of the gateway. Each serial port of the gateway acts as an active Modbus RTU master polling the Modbus RTU slaves like power meters on one end, while on the other side, the gateway operates as a Modbus TCP server polled by the SCADA system. A crucial feature of gateways supporting agent modes is an internal memory facilitating seamless data retrieval.

Agent mode communication offers several benefits. From the SCADA system’s perspective, the scan time is significantly faster than transparent mode communication. The scan time comprises only the duration of the Modbus TCP request and response since there is no waiting for the Modbus RTU leg of the polling process in the SCADA system.

Another advantage is that agent mode enables the transfer of all device-generated data in a few packets. The gateway acts as a data repository delivering the requested information from the SCADA system’s viewpoint. In its Modbus RTU role, each serial port of the gateway actively polls different meters to collect data from their diverse registers. The accumulated data is continuously stored in the gateway’s internal memory, requiring only a TCP channel to transmit the requested data in a few packets without the complexity of setting numerous commands in SCADA. For any system integrator, smooth integration is a top priority. In agent mode, the gateway in its RTU master capacity can execute multiple Modbus commands efficiently. To simplify configuration and save time, some gateway brands support comma-separated value (CSV) files that can be effortlessly set up and imported into the gateway using MS Excel, a significant benefit particularly for extensive deployments.

Moxa’s Innovative Solutions

To discover more about the optimal strategy for reducing scan times by upgrading your system, download our white paper: Improving SCADA Systems with a Modbus Gateway.

For further insights on our solutions, download our comprehensive brochure.