Understanding Smart Sensors - Nomads.usp

Mechatronics and Sensing Systems 263A four-element gas analyzer is achieved by a three-chip hybrid configuration.Two dual-window gas detectors and a control interface chip are in thehybrid package. The gas detector process is compatible with CMOS processingso the combination eventually could be integrated into a single monolithicchip.The control chip is capable of controlling four gas-detecting elementsindependently. All elements can be monitored and programmed simultaneously.A temperature of 1,000°C can be controlled for each chip. The chipcommunicates with a local-node MCU or a remote processor through aneight-pin standard interface. The front-end standard is capable of operating upto 32 sensors, 32 actuators, 32 self-test commands, and 32 special-functioncommands for different applications.Another array approach for gas sensors has a 3-by-3 matrix of identicalsensors on a single chip 4,466 by 6,755 mm [9]. The nine sensors are interdigitatedgate electrode field-effect transistors (IGEFETs). A single version ofthis design has selectively and reversibly detected 2 ppb of nitrogen dioxide anddiisopropyl methylphosphonate, two pollutants that can adversely affect thenvironment. By using a Fourier transform signal processing technique andimplementing a pattern recognition algorithm, it is possible for this type ofsensor to operate as an electronic “nose” for detecting and identifying the constituentsof a multicomponent gas mixture.Photodiode arrays are becoming cost effective for manufacturing inspection,quality control, process monitoring, and other industrial applications. Asilicon CCD has a spectral range from 200 to 1,100 nm. Devices can be manufacturedwith detector elements as small as several microns in width and withup to 2,048 elements. After amplification and digitizing for signal processing,the readout can routinely reach more than 1 MHz. A complete spectral measurementcan be made in only a few milliseconds. Optical design, electronicdesign, and mechanical packaging must be coordinated in a mechatronicsmethodology to allow those devices to be used in a laboratory as well as amanufacturing environment [10].An infrared focal plane array, which operates much like the human retina,has been designed and fabricated [11]. The array, called a neuromorphic sensor,has logarithmic sensitivity to avoid saturation common in conventionalthermal imagers. It also performs pixel-based sensor fusion and real-time localcontrast enhancement. The sensor contains a backside illuminated, 64-by-64array of 100-mm indium antimony photovoltaic diodes. A CMOS IC performsthe readout function as well as two-dimensional averaging across the chip. Theneuromorphic sensor mimics the neural network process by interconnectivitybetween each pixel’s four nearest neighbors. A digital computer performing the