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By Rick DeMeis, Associate Editor -- Design News, December 21, 1998
Torque without strain
"TorqStar sensors do not use strain gauges to measure torque," notes Mike Brown, sales engineer for Lebow Products. Instead, transducers measure the magnetic field that surrounds a magnetoelastic sensor. Depending on application, sensors, such as fluxgate, Hall-effect, or magneto-impedance, extract torque at frequency response rates up to 10 kHz. And maintenance associated with slip rings and brushes is eliminated. Since the sensor shaft isn't necked down to mount strain gauges, mechanical overload resistance is sustained. Full-scale capability ranges from 50 to 1,000 in-lb in applications including motion control, fastening, dynamometers, and tool monitoring. Accuracy is 1% at sensor full scale. Mounting configurations are NEMA flange-mount, keyed shaft, square drive, or customer-specified. Optical encoders for speed/angle measurement are available.
Lebow Products:
Product Code 4521
Laser senses vibration
The Orion laser Doppler vibrometer from Nicolet Technologies optically measures vibration on almost any type of surface in production or research applications. Bill Harrison, product manager, notes, "Orion is completely non-contacting, providing an accurate measurement without affecting the dynamics of the structure being measured." With a range up to 7m, it is possible to obtain measurements at points not accessible with standard transducers. By measuring the Doppler shift of the laser beam, Orion can make off-axis measurements. Vibrations from 5 Hz to 80 kHz can be measured and switchable low- and high-pass filters can limit the measurement to the frequency range of interest. Standard ±10V analog output allows use with common FFT analyzers or data-acquisition systems. Applications include: production testing of engines and drive trains, or delicate structures such as hearing aids and micro sensors; pyroshock measurement; and machinery maintenance.
Nicolet Technologies:
Product Code 4525
Sensor learns low-contrast
The MINI-BEAM® ExpertTM photoelectric sensor uses a built-in microprocessor to "teach" itself to detect objects, even clear materials. According to Chris Benson, product specialist at Banner Engineering, "Especially significant, the sensor is taught by simply pushing a single, sealed button. This point-and-push teaching is quick and simple." The microprocessor software recognizes low-contrast conditions and expands the sensitivity range before computing the optimal setting for differentiating between the received light signals from targets and background. Thus, for example, the Expert can detect white labels on white bottles or colormarks on a continuous web. A choice of LED light source colors allows maximum color sensitivity. Sensing modes include: proximity, polarized retroreflective, convergent beam and fiber optics.
Banner Engineering: Product Code 4522
Shape Tape measures up
"Low-cost plastic optical fibers and software are the keys to Shape Tape," according to Lee Danisch, president of Measurand, developer of the product. The device was originally developed for human control of a two-arm robot. An array of 0.25-mm diameter fiber-optic loops paired to sense twist and bending are embedded along a ribbon, providing 3D position and orientation of the ribbon. The fibers are treated along a 2-mm section on one side in their tight loop region to loose light in proportion to bending, up to 30% of available light throughput. Sensitivity is such that radii of more than 1 km can be resolved. The circuit employs no switching and is not susceptible to electromagnetic radiation. Uses include robotic arm positioning and feedback, 3D CAD input, motion capture, image processing, process control, and medical diagnostics.
Measurand: Product Code 4520
Stable measuring
Senior Flexonics, Metal Bellows Div.'s optically based distance measurement resists temperature and pressure changes. The sensor's diode-laser beam reflects from a corner cube back to a detector, with reflected light proportional to the distance. The cube reflector is insensitive to small rotational displacement. Chief engineer Randy Moore says, "There was nothing previously available to measure in the 2- to 24-inch range." Mounted on the sweeper of a gas-accumulator bellows, the no-moving-parts device was originally geared to measuring gas volume in enclosed environments such as gas or vacuum tanks, but is now available for custom configured applications. The solid-state system has no moving parts prone to installation errors and wear. It replaces cable/pulley designs weighing twice as much.
Senior Flexonics: Product Code 4523
Chips detect pressure
UltraStableTM HIT micromachined silicone pressure sensors from EG&G IC Sensors have twice the accuracy (0.5% full-scale output) and more than double the temperature range (-20 to 85C) of its previous sensor chip offerings, but at the same price. Design, material, and fabrication improvements reduce time- and temperature-dependent drift of sensor output. The devices use a silicon micromachined diaphragm into which four piezoresistive strain gauges are diffused. The pressure sensors are available in dual-in-line packaging for pc-board mountable use. High-volume but low-cost applications include: medical and calibration equipment, process control, factory automation, air-flow management, avionics, and leak detection. Various pressure ranges, from 0-10 and 0-100 psi can be provided.
EG&G IC Sensors: Product Code 4524
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