With systems getting larger and processes becoming more complex, the need to measure and control all aspects of your plant in a central location is critical. Whether you have a single factory or multiple sites, getting all the relevant data to a single location has always been a challenge.
In the past, this would have been done with expensive Programmable Logic Controllers (PLCs) with a high density channel count, long cable runs and in some cases, a compromised location. Using a system with distributed I/O, the disadvantages of high channel counts and expensive controllers can be overcome and additional benefits can be realised.
The main characteristics of a distributed I/O system are small field devices with a wide range of I/O options such as digital and analogue channels, temperature measurements and counter inputs. These modular devices give a flexibility that can not be achieved with traditional devices.
A significant benefit of this distributed approach includes short cable runs for signals since the measuring devices are located close to the sensors. Direct connection of sensors eliminates the need for signal conditioning while providing standard signal inputs for those unusual and specialised sensors.
Utilizing reliable and conventional communication buses such as Ethernet and RS485 with protocols such as Modbus/TCP, Modbus/RTU, Profibus, and even ASCII, modules can be integrated into existing networks and systems, giving a low cost, flexible upgrade path.
These advantages can be extended to the software, presenting data in a standard format for new and existing platforms such as OPC (Open Process Control), Modbus, SNMP (Simple Network Management Protocol), and the other protocols like email and SMS messages on the cellular network. With the use of appropriate gateway devices, modules can be connected to existing legacy systems such as a plant wide Distributed Control System (DCS) and simply reconfigured if the system is upgraded or replaced.