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Forget what you know about optical encoders; ; disc crashes, premature bearing failure, and signal drift are problems of the past with Dynapar's new NorthStar brand of harsh duty optical encoders.

The Module

At the heart of this technology is the photo module, comprised of an ASIC, LED, lens, and lead frame. The chip (or ASIC) is a single phased array opto-ASIC that eliminates the need for potentiometers and a multitude of discrete components. Phase quadrature and symmetry are designed into the ASIC at the wafer level, eliminating signal drift due to time and temperature. The LED is regulated to only 20% of its power rating, increasing life and subsequently MTBF. The ASIC, LED, and lens are embedded in a molded lead frame which comprises the complete sensing module. The phased array ASIC and collimating lens allow for the use of a metal or Mylar disc and a large "air gap" of 0.030 inches, a factor of 10 times that of many conventional glass disc encoders. In addition, no separate masks are required, helping to assure performance over a wide temperature range of -40 to +100 degrees centigrade.

The Disc

The discs used are made of 303, full hard stainless steel or 100° C plastic for rigidity, unlike many encoders that use fragile and expensive glass as the disc material. When coupled with the module and its .030" air gap, higher shock and vibration resistance is possible.

The Bearings

The bearing assembly used consists of a CNC machined frame and a double-row 100 pound load rated ball bearing and 10mm passivated stainless steel shaft. What makes this bearing assembly unique and more robust is the retention method used. The bearing is secured to the shaft on one end by an external retaining ring and on the other by a high-load rated bolt. Many typical encoders use adhesives as the sole means by which to secure the bearing and shaft, sometimes resulting in premature failure.

The Seals

The use of double-labyrinth seals for the housing and contact seals for the shaft mean the ultimate in wash down protection. In addition, the assembly screws used in the housing are mounted outside of the seals, not comprising their integrity. Put all this together in a tough, cast housing with an option for stainless steel or nickel plating on several models and you have one tough package to beat. For hazardous environment use in such industries as oil and gas, ATEX certification is available for intrinsically safe operation.