Modbus is supported by many industrial devices, including those offered by Campbell Scientific.
Not only can intelligent devices such as microcontrollers and programmable logic controllers
(PLCs) communicate using Modbus, but many intelligent sensors have a Modbus interface that
enables them to send their data to host systems. Examples of using Modbus with Campbell
Scientific dataloggers include:
l Interfacing dataloggers and Modbus-enabled sensors.
l Sending and retrieving data between dataloggers and other industrial devices.
l Delivering environmental data to SCADA systems.
l Integrating Modbus data into PakBus networks, or PakBus data into Modbus networks.
7.2.2 Modbus protocols
There are three standard variants of Modbus protocols:
l Modbus RTU — Modbus RTU is the most common implementation available for Modbus.
Used in serial communications, data is transmitted in a binary format. The RTU format
follows the commands/data with a cyclic redundancy check checksum.
NOTE:
The Modbus RTU protocol standard does not allow a delay between characters of 1.5 times or
more the length of time normally required to receive a character. This is analogous to “pizza”
being understood, and “piz za” being gibberish. It's important to note that communications
7. Communications Protocols 84
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