Designer's corner 3-2-98

March 2, 1998 Design News

Designer's corner

Useful technology for your idea file

Polymer suppressor

Microelectronic devices must meet IEC 1000-4-2, the "yard stick" for evaluating ESD (electro static discharge) immunity, before being lobbed into the European market. The trend toward lower operating voltages, increased circuit speeds and higher IC densities increase demand for equally fast and small transient voltage suppressors (TVS).

Capacitance of existing TVS technologies, such as multi-layer varistors and silicon-avalanche diodes, may distort signals at very high data rates. SurgX's voltage-variable polymer technology, combined with metal film on ceramic deposition, achieves outstanding benefits in ESD protection such as:

Under-the-connector, "zero foot-print," design.

Ed Carter, Bussmann Div., Cooper Industries, Box 14460, St. Louis, MO 63178; (314) 527-3877.

Bearing analyzer

Routine checks of bearing condition can save unnecessary damage and hours of downtime. A laptop computer and accelerometer can simplify the procedure.

Software running on the computer analyzes the acceleration signals in the frequency and time domains. The operator obtains a damage diagnosis by selecting the bearing from a database. The computer then automatically examines the envelope power spectrum using fuzzy logic.

Diagnosis indicates whether damage has occurred and gives the type of damage. Structure-borne noise and vibration from other parts of the machine are effectively masked out.
Rocco Docimo, FAG Bearings Corp., 200 Park Ave., Box 1933, Danbury, CT 06813-1933; (203) 830-8133.

Hard-nose sensor

Many proximity sensors employ a non-metallic face which is prone to damage. This sensor's stainless-steel face and relatively low oscillator frequency--designed to counter the electromagnetic skin effect produced in the metal face--overcome the problem.

Equally important is it's sensing principle, which calls for a transmitter coil located between two balanced receivers. The transmitter produces a magnetic field which changes with the passage of metal objects and causes the receiver voltages to cancel out.

This method eliminates previous disadvantages such as reduction factors for different metals or susceptibility to magnetic fields.
Robb Black, Turck Inc., 3000 Campus Drive, Plymouth, MN 55441; (800) 544-7769.

Labyrinth interlock

Labyrinth seals protect bearings from contamination using a "maze" or indirect path, formed by the rotor and stator. The more elaborate the path, the harder it is for contaminants to infiltrate the bearing. As path area increases, so does heat generation. Using PTFE (polytetrafluoroethylene) for the rotor and stator, means increased path area, without increased friction. High-memory retention after deformation permits the material to be manually deformed to interlock the rotor and stator. The result is a chemical resistant, unitized cartridge seal, that's installed in one piece.
Jeff Grudzien, Garlock Sealing Technologies, 1666 Division St., Palmyra, NY 14522; (800) 448-6688.

Flexible collimator

No thicker than three hairs, the silicon beams of this photospectrometer eliminate manual recalibration. Instead, beam flexing alters aperture size to modify the passage of light.

Two plates, micromachined from silicon, define aperture size. A stationary upper plate establishes slit height. A lower plate, part of the elastic-beam structure, comprises six slits of varying width.

Two cogs and a micromotor initiate translation. Changing aperture size takes less than one second; double-beam symmetry ensures millimeter-long linear displacements with a position accuracy better than 0.01 micrometers.
Hans van den Vlekkert, CSEM Microsystems, Rue Jaquet-Droz 1, Case postale 41, CH-2007 Neuchatel, Switzerland, Tel: +41 32 720 51 11, Fax: +41 32 720 5700.