Fieldbus I/O System Options
The fieldbus I/O system has a variety of options that determine how the I/O system is configured. You can choose analog and/or digital signals as needed. You will also need to determine which industrial network or protocol your fieldbus system will use. Finally, would you choose a distributed I/O system or a remote I/O system?
Analog I/O vs. Discrete I/O
First, let's determine the difference between analog I/O and discrete I/O. Discrete signals, also known as digital signals, only send and receive certain values, such as "on" or "off". A perfect example is a light switch. Lights can only be turned on or off. If you want to dim the lights, you need an analog signal. Analog signals can send and receive variable signals or detect multiple states.
Distributed I/O and Remote I/O
Distributed I/O modules are located throughout the machine and data is collected over an industrial network. Multiple processors control different parts of the operation, and the processors share data with each other to coordinate overall machine operation.
With a remote I/O setup, the control processor remains in a remote location or at a distance from other I/O modules. Since the data is acquired over an industrial network, the entire machine operation can be monitored from an off-site location. This type of setup is therefore useful when modules are located in hazardous areas.
What is an industrial network?
To connect your equipment to a fieldbus system, you will need to select an industrial network protocol to use throughout the system. This network will allow you to collect data from a variety of devices. Examples of popular industrial networks include Profibus, DeviceNet, Modbus, and EtherNet/IP.
Choosing the right industrial network for you depends greatly on your requirements and specifications. In the Industrial Networking Basics video linked below, the speaker explores the advantages and disadvantages of several popular networks. Typically, you will need to narrow down your choices by asking the following questions:
- What types of topologies does the network support?
- How far can it go without repeaters?
- What are the data rates?
- How many nodes does the network support?
- What media does the network use?
- What type of communication does it use?
Gateways
Gateways come in handy when you want to upgrade or remodel an existing network. They also allow changes to the communication language or protocol. An example you can use is if you are converting from traditional MODBUS RTU/ASCII to MODBUS TCP.