The most common gateway in energy monitoring and machine data projects connects RS-485 Modbus RTU devices to a Modbus TCP network. We compare three popular families from their published documentation.
Meters, drives and sensors often have only an RS-485 port, while software and PLCs live on Ethernet. A Modbus gateway sits between them: it acts as a Modbus master on the serial side and answers Modbus TCP requests on the network side. This article compares three families you will meet in quotations. It is not a hands-on test, and specifications below come from each maker's public pages.
Tap or click the diagram to enlarge it.
Each serves the same basic job at a different level of ruggedness, security and price.
1-, 2- or 4-port Modbus RTU/ASCII to Modbus TCP gateways, in standard and advanced lines.
A 1-port Modbus gateway from the EKI-1200 family (2- and 4-port siblings exist).
A compact, low-cost serial-to-Ethernet module with a Modbus gateway function.
Figures are from the maker pages listed under Sources. Where a page was silent we say so rather than guess.
| Specification | Moxa MGate MB3000 | Advantech EKI-1221 | USR-TCP232-410S |
|---|---|---|---|
| Serial ports | 1, 2 or 4 × RS-232/422/485, software-selectable (DB9) | 1 × RS-232/422/485 (DB9) | 1 × RS-232 + 1 × RS-485, usable together |
| Ethernet | Standard: 1 × 10/100. -G2: 2 × 10/100 (cascade or dual subnet) | 2 × 10/100 for LAN redundancy | 1 × 10/100 |
| Modbus TCP connections | Standard: 16 masters. -G2: 32 clients and 32 servers | 16 (client mode) / 32 (server mode) per serial port | Multi-host polling, up to 16 hosts |
| Supply | 12–48 VDC; -G2 has redundant dual inputs | 12–48 VDC, redundant dual inputs | 5–36 VDC in the spec table; 9–36 VDC elsewhere on the page |
| Temperature | Standard: 0 to 55/60 °C. -G2: −10 to 60 °C; -T: −40 to 75 °C | −10 to 60 °C; I and CI models −40 to 75 °C | −40 to 85 °C |
| Isolation | Ethernet 1.5 kV magnetic; serial isolation depends on the model | CI models: 2 kV serial-to-Ethernet and serial-to-power | Ethernet 1.5 kV (another section says 2 kV) |
| Housing and mounting | Metal housing, IP30 | IP30, DIN-rail or wall | Wall mounting, 82.5 × 86 × 25 mm |
| Security features | HTTPS/TLS 1.2 on MB3280/3480; -G2 meets IEC 62443-4-2 SL2 requirements | Security functions refer to IEC 62443-4-2 | MQTT with SSL; TCP client with SSL |
| Warranty | 5 years (standard series page) | Not stated on the page we read | 2 years |
The best gateway is the one that fits the site, not the longest spec list.
This is a desk-based comparison using the manufacturers' public documentation, read in October 2026. We did not bench-test these units for this article. Specifications, firmware and model status change, and even a manufacturer's own pages can disagree — always confirm in the current datasheet before you specify or buy. Brand and product names belong to their owners; mention here is not an endorsement.
Tell us what devices you need to connect and we will recommend a gateway and a wiring plan.
