Barcode reader offers precise position

Optically determining position offers freedom from mechanically wearing parts and elimination of slipping. In addition, the BE-90 barcode-based measurement system from TR-Electronic can handle non-linear movement and can be used on circular and curved surfaces. Such capability is useful for applications including storage-rack control and lifting, cranes and shuttle cars, transfer machines, and overhead conveyors.

A thousand times per second, the visible red (670 nm) laser-based detector, similar to rotating-mirror scanned retail price checkers, scans a tape with a sequence of barcodes attached to the component whose position needs to be tracked.

The tape, 10 to 160 mm away from the detector, can be up to 10 km long before barcodes would become repetitive. Jorge DaSilva, applications and product support supervisor, notes the individual side-by-side barcodes provide course resolution. Then a proprietary scaling architecture determines position of a standard point within the barcode to a resolution 0.1 mm with a reproducibility of plus or minus 1 mm. The system can be programmed to read in any units or desired intervals. By using distinct barcodes on the tape, no homing or referencing is required after a power interruption.

The tape itself is a polyester film 0.08 mm thick that is resistant to UV light, oil, and acids. An acrylic adhesive bonds the tape to the desired surface. Because the tape conforms to the surface to which it is attached, whatever then happens to the surface also happens to the tape. DaSilva says, for example, a defect due to a dent would be detected, and the system will iterate across the flaw to compensate and could be programmed to report the error detection through the BE-90's RS232 com port.

The BE-90 system can be used in IP 65 (NEMA 12) environments and in temperatures of 0 - 40C. With an optics heater, operation is possible down to -30C. Supply voltage is 10 - 30V dc.

CONTACT: Jorge DaSilva, TR-Electronic 1890 Crooks Rd., Suite 200, P.O. Box 4448, Troy, MI 48084 Tel: (800) 265-9483; Fax: (519) 452-1177 e-mail: [email protected]www.trelectronic.com; or enter 509 at www.designnews.com/info.