04 - How does Fieldbus lower the cost?

Economic benefits spring mainly from the fact that less hardware is required. Of the expensive DCS only the operator console remains. Due to its non-critical nature, a PC or IPC (Industrially hardened PC) with off the shelf software may be used, even for large systems.

Fieldbus devices may perform multiple measurements, control and computations. The number of transmitters may be reduced, single loop controller and computational units will not be required, again saving cost.

Though Fieldbus, the device price may initially be higher than conventional or smart, the reduction in devices and wiring with associated cable trays and marshalling boxes will make the system cheaper. Manufacturers can no longer rely on proprietary technology to keep prices up. Open competition enabled by a playing field levelled by Fieldbus will reduce prices.

Cost is not only price... There are substantial long-term savings resulting from the increased information flow in terms of diagnostic information and easier calibration etc.

Many Fieldbus transmitters will be of a multiple variable type. For example, dual channel field mounted temperature transmitters measuring two temperatures being able to transmit both variables in real time. Since a single transmitter can condition several sensors, the cost per measurement point will be lower. This is the ideal combination of price and performance. Previously multiple temperatures sensors where typically handled by conditioners in the control room with long wires into the field, having a penalty on accuracy and noise immunity due to factors like lead wire resistance, poor or no thermocouple compensation wire and poor routing of low level signals. Multiple variable technology makes it economically viable to use field-mounted transmitters right next to the sensors for immediate interface and transmission in the high integrity digital domain. Added advantage is the capability to perform high and low selection, redundant sensor voting, average and difference calculation in the field.

Fieldbus helps companies increase productivity, flexibility, quality and comply with ever more stringent environmental regulations, and at the same time lower their operating cost. Fieldbus is the means whereby companies will stay competitive well into the 21st century.

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