Some of the biggest advances revealed at Sensors Expo 2008, held June 9-11 in Rosemont, Ill., involved some of the smallest technology. A host of companies was on hand and eager to display their hottest developments in microelectromechanical systems (MEMS) motion sensors.
For example, Kionix offered its latest three-axis MEMS accelerometers. The KXSD9, which comes in a 3- by 3- by 0.9-mm land-grid array (LGA) package, targets the consumer market. Housed in a 3- by 5- by 0.9-mm LGA, the KXRB5 suits high-performance applications. Both feature low-power and low-noise specifications.
According to SignalQuest, its SQ-MIN-830P is the smallest tilt and vibration sensor available today. Measuring 1.4 by 3.2 mm, it’s about a third the size of its competition, the company says. SignalQuest takes MEMS chips from other companies, adds value to them, and incorporates them into the SQ-MIN-830P’s design.
Also on display, the CGR20 and CRS09 MEMS gyroscopes from Silicon Sensing Systems are based on a patented silicon ring gyroscope technology. The CGR20 is designed for automotive applications, while the CRS09 suits stabilization, navigation, and testing apps.
The ADIS16365 industrial MEMS inertial measurement unit from Analog Devices provides six degrees of freedom. Part of the company’s iMEMS family of sensors, it comes in a compact module that’s 23 by 23 by 23 mm (see the figure). It also reduces power consumption by at least 20% compared to the previous-generation ADIS16355. Its startup time is about 10 times faster, and it improves stability by 50% as well.
Designed for OEMs, the three-axis SCA3000 from VTI Technologies provides equal performance in all three axes. It also boasts 2.35- to 3.6-V operation, a 1.7- to 3.6-V digital I/O, selectable frequency response, and a 64-sample/axis buffer memory for output acceleration data. Its advanced features enable significant power and resource system-level savings. An interrupt signal can be triggered by motion and freefall. And, it comes in a 7- by 7- by 1.8-mm package.
The AssetOverseer SS three-axis accelerometers from Sporian Microsystems Inc. consume just 15 µA from a supply of 2 to 5 V dc under all operating conditions, making them ideal for battery operation. The three members of the family can withstand ±200, ±500, and ±1000 g of shock, respectively, all in 0.75- by 0.75- by 0.5-in. packages.
Not all MEMS ICs are created equal. MEMS device manufacturing can be very difficult when the application involves harsh requirements. Tronics Microsystems faced such challenges when it needed to create an ultra-miniature wireless and implantable pressure sensor for medical applications.
The sensor had to be implantable in a catheter or a lead. It also had to have the lowest battery-operated power consumption, as well as low and precision drift and temperature stability specifications. It had to be isolated from blood, tissue, and saline solutions via compatible encapsulation and hermetic sealing as well.
Tronics integrated a single-crystal capacitive pressure sensor and a 16-bit delta-sigma ASIC analog-to-digital converter (ADC) with a temperature gauge, all in a titanium package. The device is housed in a tiny implantable biomedical pressure sensor developed by Tronics International that fits in medical catheters.