Showstoppers at Sensors Expo

E-mail Ed Ramsden

One of the best parts of Sensors Expo is getting to see new and interesting products, and getting to spend some time talking to the people who make them. While there were lots of neat sensors on display, I found a few especially memorable.

There are many linear optical and magnetic encoders out there, but the one big problem with most of these is that they provide only relative position—when you turn them on, you need to 'home' them, and then continuously keep track of their motion to know their true position. Renishaw's InAxis absolute position linear shaft encoder solves this problem in an incredibly elegant manner. Unlike typical encoders that use uniform periodic scales, Renishaw's device uses a pseudo-random, nonrepeating patterned scale built into a steel shaft. An array of magnetic sensors in the encoder head interpret this pattern to determine the encoder's location without having to access a distant home reference. The scale can be fabricated to lengths of several feet before the pattern repeats, and is said to provide positioning linear resolutions down to the 0.5 µm level.

Infrared thermal imaging sensors offered by both Heimann and Lapis Semiconductor also caught my eye. While thermal imaging has been around for years for military and high-end instrumentation applications, these 'kilo-pixel' range sensors bring temperature imaging to consumer, personal medical, mainstream security, and other low-cost/high-volume applications. With imaging arrays of up to 48 x 47 pixels (Lapis) and 64 x 62 pixels (Heimann), these sensor arrays can provide enough resolution to identify hot spots in equipment, or distinguish multiple people from a background in a scene. Two important features of these products are that they can operate without expensive thermoelectric cooling systems and that they integrate enough electronics to provide a user-friendly interface (a digital output in the case of Heimann and a compensated analog signal in the case of Lapis).

While a comfortable mattress is good for everyone, it is especially important for those who may be confined to bed for extended periods of time. Vista Medical/PatienTech's pressure sensitive fabric provides the ability to create 2-dimensional maps of pressure across a mattress or any other large object, potentially allowing the mattress to be adjusted to reduce the incidence of bed sores and to provide other benefits for those who are bedridden. PatienTech's fabric is based on a pressure-sensitive semi-conductive core with a resistance that varies as a function of applied pressure. This core is sandwiched between fabric layers with X-Y conductive patterning to allow for localization. These internal layers are protected from moisture and friction by external non-active fabric. In addition to medical mattress applications, Patientech also sees a future for this sensor in other places that might be enhanced through biomechnical pressure monitoring, such as chair seats, shoes, and even athletic clothing.

Although I really liked all of the above products, for jaw-dropping technical cool I found Metria Innovation's 6-DOF spatial position sensor hard to beat. This device measures both the spatial X,Y, Z coordinates and the angular rotations of a special Moiré-patterned retroreflective target using a high-resolution digital camera and proprietary image processing software. The Moiré patterning produces an image that is highly sensitive to the target's angle with respect to the camera, enabling measurement of the target's rotational position. The system as a whole can measure the target's linear position with a resolution of 0.1 mm in the X and Y plane and 1 mm in the Z (depth) axis and can also measure pitch, yaw, and roll with 0.05° resolution over a region of several cubic meters. In addition to measuring position, the system's speed (up to 200 frames/second) and high resolution also enables it to remotely measure vibration in real-time from multiple targets!

Ed Ramsden is a Senior Design Engineer with Sensata Technologies, Inc., Attleboro, MA. He can be reached at 508-236-1495, [email protected].

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