A smart sensor, according to generally accepted industry definitions, combines a sensing element, analog interface circuit, an analog-to-digital converter (ADC), and a bus interface, all in one housing. Making the grade against the newest generation of smart sensors, however, means that additional functionality must be included, such as self-testing, self-identification, self-validation, or self-adaptation. Of particular interest and importance to designers are such smart sensor capabilities as self-calibration and self-diagnosis, the ability to use signal processing, and multi-sensing capabilities.
The market research firm Global Industry Analysts, Inc. pegs the world smart sensors market at $7.8 billion by 2015. Smarter and smaller than ever before, these sensors are rapidly making their way into health care monitoring, collision avoidance (including air traffic control), high-speed machinery, automotive applications, and even oil platforms.
Whether measuring inclines, linear movement, or acceleration, there are a myriad of truly smart sensors now on the market, and more are popping up regularly. They are providing real resource savings in terms of design time and component cost and most of all, are breaking through long-standing barriers.
Here’s one, for instance: Historically, linear position feedback was hamstrung by the physical limitations of system noise, signal attenuation, and response dynamics, causing designers to “tweak” their designs to overcome these challenges. Today, fast microprocessors and digital signal processors are beginning to bring new capability to sensors such as Honeywell’s first non-contacting linear position product called SMART, which stands for Superior Measurement, Accuracy, Reliability, and Thinking.
The SPS-L075-HALS device (Figure 1) itself combines magneto-resistive (MR) sensors and an ASIC that together enable the accurate measurement of any linear movement. The SMART Position Sensor provides a self-diagnostics feature and data gathering for enhanced reliability and closed-loop feedback control. It’s simple, noncontact design eliminates mechanical failure mechanisms, reducing wear and tear, improving reliability and durability, and minimizing downtime. It also is “smart” enough to replace several sensor and switch components and the extra wiring, external components, and connections that previously accompanied them.
Figure 1: Sensor output performance charts showing ideal outputs of analog and digital versions.
Two new SMART position sensor non-contacting configurations recently joined the SPS series that are able to sense the position of a magnet relative to the sensor in either of two ranges: 0° to 100° and 0° to 180°
The 100° configuration accurately measures values to 0.06° while the 180° configuration measures values to 0.11°. The SPS series sensors also include the 75- and 225-mm linear configurations. The sensor is, to date, claimed to be the most accurate device available in the industry; the 75-mm configuration accurately measures values down to 0.05 mm, while the 225-mm configuration accurately measures value down to 0.14 mm (analog) and 0.0035 mm (digital).
Designed for use in harsh environments including extreme temperatures, salt water, rough terrain, vibration and shock, the sealed package not only protects the device, but also provides a four-step installation process (1: position device; 2: drill holes; 3: mount sensor; 4: locate magnet/connect three wires), reducing installation procedures and cost. Target markets include aerospace, medical, transportation, and industrial applications.
The ADIS16203 from Analog Devices is a complete programmable 360° incline-angle measurement system in a single compact package based on the company’s iSensor integration. By enhancing the Analog Devices’ iMEMS sensor technology with an embedded signal processing solution, the ADIS16203 provides factory-calibrated, sensor-to-digital incline-angle data in a convenient format that can be accessed using a serial peripheral interface (SPI) for multiple measurements: 360° linear inclination angles, ±180° linear incline angles, temperature, power supply, and one auxiliary analog input.
Figure 2: Functional block diagram ADIS16203.
The ADIS16203 offers two power management features for managing system-level power dissipation: low power mode and a configurable shutdown feature, and is available in a 9.2 × 9.2 × 3.9-mm laminate-based land grid array (LGA) package with a temperature range of −40° to 125°C.
Applications include tilt sensing, inclinometers, platform control, stabilization, leveling, motion/position measurement, monitor/alarm devices, and robotics.
Automotive sensing needs
In a recently released study, the market research firm Strategy Analytics forecast an automotive sensor market reaching $21.9 billion by 2018. Part of this rise will be attributable to safety, fuel efficiency, and environmentally friendly improvements.
Based on capacitive 3D-MEMS technology the VTI Technologies SCA3100-D07 3-axis accelerometer (Figure 3) targets automotive sensing applications requiring high stability and vibration robustness. Featuring a digital SPI interface and stable output over wide range of temperature, humidity and mechanical noise the accelerometer was specifically designed to support the trend towards intelligent integration and smart sensing combined with improved reliability and sophisticated self-test features.
The offering covers one-, two-, and three-axis measurement from 2 to 5 g and fits into a package size measuring only 7.6 x 3.3 x 8.6 mm.
Figure 3: The VTI SCA3100-D07 three-axis accelerometer block diagram.
The SCA3100-D07 is fully compatible with VTI’s single axis accelerometers (SCA800 series) and other multi-axis accelerometers (SCA2100 series and SCA3100 series). It meets AEC-Q100 standard qualifications as well as RoHS and ELV directives and its DFL housing is suitable for SMD mounting.
Increasingly, highly-integrated smart sensors perform logic functions, rely on two-way communications, adjust for changes in their environment, and make decisions. Compared with their not-too-distant standard sensor cousins, smart sensors can now rely on self-calibration and built-in self-test — two areas that have long presented major and expensive challenges. They provide computation and communication, and many smart sensors measure multiple variables simultaneously.
The ability to provide real-time measurement of complex phenomena increases sensor value. In industrial applications, proprietary algorithms now can analyze sensor data and optimize machining, processing, speed up throughput, reduce maintenance, minimize scrap, and improve the overall product or process quality.
In the future, smart sensors will continue to shrink in size and grow in importance as they perform an increasing number of functions, and do it better than ever before. Smart sensor systems will offer greater flexibility and ease of implementation, and standards governing their use will continue to evolve.
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