The advantages of the PC to IED fieldbus system

As the requirement for smaller and smarter systems grew, sensors were designed with the intelligence of PLCs and DCSs. These devices are known as IEDs (intelligent electronic devices). The IEDs are connected on a fieldbus, such as Profibus, Devicenet or Foundation Fieldbus to the PC. They include enough intelligence to acquire data, communicate to other devices, and hold their part of the overall program. Each of these super smart sensors can have more than one sensor on-board. Typically, an IED could combine an analog input sensor, analog output, PID control, communication system and program memory in one device.

The advantages of the PC to IED fieldbus system are:
• Minimal wiring is needed
• The operator can see down to the sensor level
• The data received from the device can include information such as serial numbers, model numbers, when it was installed and by whom
• All devices are plug and play, so installation and replacement is easy
• Smaller devices means less physical space for the data acquisition system

The disadvantages of a PC to IED system are:
• More sophisticated system requires better trained employees
• Sensor prices are higher (but this is offset somewhat by the lack of PLCs)
• The IEDs rely more on the communication system