02 - Is Fieldbus easy? It sounds complicated.
As the first protocol to bring the full power of microprocessor technology into field instrumentation, Fieldbus distil countless hours of thought into every aspect. When you press a key or click to change the configuration, the effect is powerful, yet all the work has been done for you. There is no need to understand the wealth of technical strength hidden in your field device in order to appreciate it. Fieldbus is easy to use, there is no need to understand the "layers" and "baud rate", it has been taken care of by the best engineers from the leading companies in transmitters, systems and actuators.
Configuration becomes easier because it will be done the same way for basically all devices using the function block concept, no need for training on several device types or programming languages. All manufacturers use the same blocks, regardless if they are in a field device or not. Fieldbus is based on user-defined tags and standardized parameter names like SP and PV. He refers to devices by its tag. The user need not think of device address, memory address and bit numbers etc. Configuration may be edited on a PC and then down loaded to the devices in the field. If you want a flow transmitter to integrate, just instantiated the function block, no need to rewire or buy an additional device. Once physically connected, the links between function blocks may be changed, function blocks can be added and removed etc. More advanced devices may execute a virtually unlimited number of function blocks.
Procedures like calibration, range setting and diagnostics are implemented consistently between manufacturers and device types. I.e. a density and pressure transmitter from two different companies are operated in the same basic way. This reduces confusion and makes operator training easy, even though your preferred vendor for various device types is different and may change over the years.
Fieldbus already has blocks for all kinds of process control functionality like input, output, control, calculate and various types of computations forming an advanced set. Several of the blocks implement alarm. New blocks will keep getting added.
Connection is a simple task since devices are connected in parallel and terminal number matching will be a minimum. One wire will typically connect as many as twelve devices. Cable trays, conduits etc. will be drastically reduced. It also becomes easy to add devices, just hook it up in parallel, no need to run a new wire.
Fieldbus has capability to simulate input or output values or status making it possible for a single person to from the control room safely test the system response to faults and process conditions which would otherwise be difficult or dangerous to try out. Previously making such a test was troublesome. Two persons equipped with walkie-talkies were always required, one climbing on tanks and pipes in the field with a simulator. There is no need to expose anybody to an unfriendly or hazardous environment.
"Ringing out" the transmitters, i.e. match the wires in the marshalling rack to their respective devices is also much easier, apply power and connect the Host and ask for the tag and you are done!
Fieldbus devices store information useful for maintenance in the device, where it will never get lost. You may store a calibration data like when and by whom, description of the service of the device and even individual blocks may be stored, this could be e.g. "Level - Boiler 1".
A wealth of information is available in the device, which also includes wetted materials information and serial numbers. This may not only be available with the Host, but also from operator console. Accessing the device operating temperature reading allows you to see if it is operating within range. The temperature reading proves extra valuable in applications where heat tracing and winterization is used. The temperature reading is an indication of if it is working or not, so that transmitter does not fail or pipes are clogged due to solidification.
Instrument calibration and maintenance data may be stored in the transmitter database where it, unlike if stored on paper or a disk, will not be misplaced or separated from the transmitter even if the device is moved around in the plant or even shelved. This may include information like performed by whom, where, when, how and at what value calibration last was made. The information is not only more than seen before, the interoperability of Fieldbus makes it more accessible than seen for smart transmitters. This instrument management is an important feature to help comply with ISO9000 and ISO14000 requirement for updated and traceable calibration records - again a tool for better sensing.