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Understanding Smart Sensors - Nomads.usp

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Standards for <strong>Smart</strong> Sensing 281PID control system (see Section 7.1.3) that takes periodic pH sensor readingsto control the pump speed based on the measurements and pH set points [2].The mixer control is either on or off, based on the pump speed beingabove or below a given set point. The measurements are logged to a database,used in the automated control system and displayed for an operator to overridethe automated system. Figure 12.8 shows the NCAP hardware required toimplement the system with IEEE 1451 functionality.The functionality of the wastewater system is partitioned among threeNCAPs [2]. The level control and pH control are implemented on simpleNCAPs and implemented separately to meet safety requirements. The operatorsystem is implemented with a PC NCAP as the host for the system’s operatormachineinterface and data management system. Developing the software functionalityfor the system provides a rather complete use of 1451.1. Interestedreaders should refer to the standard for the full details of the example.12.4 IEEE 1451.2IEEE 1451.2 defines an interface, both the hardware and software blocks, for anetworked transducer that does not depend on a specific control network [5].pH sensorpH controlNCAPPump control actuatorMixer control actuatorNetworkLevel sensorLevel controlNCAPValve control actuatorOperator stationPC NCAPFigure 12.8 Hardware components of wastewater treatment system. (After: [2].)

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