Understanding Smart Sensors - Nomads.usp

300 Understanding Smart Sensorsport. When these PC-based standards are applied to sensing, the level of smartwill increase.13.3 Communicating Sensor Data Via Existing WiringOne way to implement advance sensing quickly is to use existing standardswith hardware and software developed specifically for sensing. Ethernet isestablished in the plant environment. Telephone lines also are being used forsensing. This section discusses both applications.13.3.1 EthernetThe existing Ethernet wiring in many plants allows the retrofitting of sensors tomonitor systems for preventative maintenance and avoid costly downtime [4].The capability of speeds up to 1 Gbps and the ability to interface directly toindustrial and personal computers make the Ethernet a low-cost alternative toother LANs. Most available data acquisition systems can communicate with a10Base-T Ethernet.More sophisticated software is required for the real-time aspect of dataacquisition. That is especially true for a network shared with general businessusers that could be disrupted [5]. Different applications such as data monitoringversus data logging place different requirements on the software. In datalogging, the connection to the computer is broken after data collection configuration.In this case, the DA device must have a high level of intelligence to storethe configurations and send data to a buffer without communication withexternal software. Data monitoring applications require less intelligence in theDA device and more in the software to perform tasks typically handled in realtime.13.3.2 Sensing by ModemCompanies are already manufacturing modem units specifically for sensingapplications. One unit, the PhoneDucer from Elwood Corp., sends formattedsensor data over telephone lines [6]. Power for the modem and the sensorscomes from the telephone line so no additional power supply or battery isrequired. The modem allows engineers to collect, monitor, and analyze datafrom a remote site using a PC running Windows and special DA software.Natural gas utilities and chemical manufacturing companies are among thecompanies that are taking advantage of this remote sensing approach.