Emerging sensor technologies

March 9, 2009
Contributing Editor Sheila Kennedy investigates emerging sensor technologies that take on G-forces, vibration, embrittlement and odors.

Researchers and manufacturers are busy pioneering new sensor technologies and adapting them from other applications. Some are improving ranges and gains while reducing size and costs, others support earlier detection of equipment deterioration. Others are developing new sensor technologies inspired by biological processes or physics.

Six degrees of freedom: Inertial measurement unit (IMU) sensors with six degrees of freedom (6DF) are making their way onto material-handling and other industrial navigation equipment. Commonly used in aerospace navigation and control, the micro-electromechanical system (MEMS) technology accurately senses and monitors rotation rate and acceleration, including up/down, left/right and forward/backward motion.

Honeywell’s HG1171 Series 6DF IMU sensor improves material handling by offering real-time stability control, improved operator awareness relative to loading and extension, motion-control feedback, and enhanced fault-monitoring and reporting. The device has a rugged metal housing and performs in a wide temperature range.

Continuous vibration monitoring: Periodic vibration sensing has proved beneficial in preventive maintenance strategies, but conventional vibration sensors are relatively costly and lack the real-time, continuous feed of information that’s sometimes necessary to allow proactive maintenance and predict degradation before it occurs. This year, Analog Devices is releasing an industrial vibration and shock sensor that continuously monitors vibration without disrupting normal equipment operation, and is priced at about one-third the cost of competing sensors. At just 5 mm square, the single-chip iMEMS ADXL001 sensor either can be mounted on existing factory equipment or designed into the motor-control circuitry.

The ADXL001’s high resonant frequency (to 22 kHz) detects motor-bearing vibration and irregularities much sooner than conventional sensors, which typically operate at a lower sampling rate (5 kHz max). The MEMS-based sensor requires no calibration, operates in a wide temperature range, and is suited for a variety of applications and hazardous industrial conditions.

Pipeline integrity sensing: To avert the failure of pipelines carrying hydrogen fuel, a sensor has been designed to detect the accumulation of excessive amounts of hydrogen in coated pipeline steel. Hydrogen slowly diffuses into the metal of conventional pipelines and gradually causes embrittlement. According to the National Institute of Standards and Technology (NIST), high-strength pipeline steels tolerate only a few parts per million (ppm) of hydrogen before significant problems arise. The new technology detects the agents that cause pipeline flaws and cracks before the defects actually occur.

The prototype sensor developed by researchers at NIST and the Colorado School of Mines (CSM) sends alternating current through the pipe and measures impedance changes, which indicate hydrogen content in the steel and overall pipe integrity. The NIST/CSM sensor can measure hydrogen content levels well below 1 ppm in pipeline steels. It’s nondestructive and noncontact, about 4 in. square in size, and portable.

Bio-inspired electronic nose: A biological approach to detecting chemicals has potential for use in monitoring industrial processes and sniffing out environmental contaminants. The chemical sensor technology developed by researchers at NIST is capable of distinguishing hundreds of chemical compounds. It leverages eight types of sensors and semiconducting sensing materials placed on top of 16 MEMS microheater platforms developed previously at NIST. Scanning across 350 temperature increments increases the number of sensors to 5,600 to simulate the performance of sensory neurons in the nose. Rather than exposing the sensor to all possible chemicals, the tiny odor-recognition device learns the chemical signatures, first by discriminating between broad chemical classes, and then by using that knowledge to generalize about new smells at the sub-class and specific-composition levels.

Physics-inspired magnetic sensor: The potential for high-efficiency ceramic engines to replace internal combustion engines is increasing. Most magnetic sensors lose the ability to operate at the high temperatures ceramic engines will require. This isn’t the case with indium antimonide magnetosensors.

Using classical and quantum physics theories, University of Chicago scientists, with support from the U.S. Department of Energy, discovered that fabricating the magnetic sensors using a slightly diluted semiconductor material allows the sensor to function at hundreds of degrees without degradation. The two methods that achieve this goal include introducing impurities of a few ppm, or disordering the material and fusing it with heat.

E-mail Contributing Editor Sheila Kennedy, managing director of Additive Communications, at [email protected].

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