Choosing Between Different Types of Modbus Data Acquisition

Are you considering Modbus for your data acquisition needs but are unsure what setup to use? We have the answers you’re looking for, so read on.
At its simplest, Modbus is a serial or network communications protocol designed to transmit data between industrial systems. Originally launched by Modicon as an open communication standard, it was quickly supported by many industrial PLC manufacturers and is used today by thousands of industrial instrumentation manufacturers.
It is used extensively in many different industries on various types of industrial networks. Read on to learn how to choose between different types of Modbus data acquisition.

Modbus devices are used in Supervisory Control and Data Acquisition (SCADA) to gather information from the field equipment or send data to field equipment. It is an open-source protocol. Modbus functions well with a variety of device types from thousands of different vendors. Modbus utilizes a simple message structure.
The Modbus Client or Controller starts the communication by sending a message, and the server receives the message and responds by sending back a message with the information requested. One Modbus Controller can send messages to over 200 servers, as each server has its own unique address. The individual server responds with the information requested.
Additionally, field equipment is generally Modbus RTU, as they can be daisy-chained to communicate with each other, which reduces cabling and hardware. Once the equipment gets into the control room, Modbus TCP is the ideal option due to its speed. However, we are seeing a move to field equipment now becoming equipped with Modbus TCP.

Modbus RTU is serial communication and can be either RS232 or RS485. The difference between Modbus RTU RS232 and Modbus RTU RS485 is enormous. Generally, Modbus RTU RS232 should be avoided due to the massive advantages Modbus RTU RS485 has. Modbus RTU RS485 can work on multiple drop networks and a range up to 1000 feet.
The Modbus RTU RS232 can only be used in short range, generally below 50 feet, and is not powerful enough to support multi-drop servers. The best bet is the Modbus RTU RS485 for your field applications.

Technically, Modbus RTU and Modbus TCP is the same protocol, but the Modbus RTU is a physical serial cable that mainly runs on an RS485 two-wire cable with multi-drop connection. The Modbus TCP is a serial package that runs on an ethernet Cat5 or 6 cable and is terminated with an RJ45 internet port. Each cable needs to run to a router.
Thankfully, we offer a wide selection of Modbus RTU and Modbus TCP compatible data acquisition modules.