The Versatile QD787 Optical Encoder


This is a picture of the QDI Model 787 Hollowshaft encoder and a loose flex-mount showing the tabs bent 90 degrees for mounting to a surface larger than the diameter of the encoder.  The motor shaft would be inserted into the brass hub and tightened by two setscrews located 120 degrees apart.

Notice the groove in the housing of the encoder.  It is designed to allow infinite adjustability; allowing the technician to align the index pulse to a mechanical location on the machine used for homing or reference.  This is called an encoder “Servo Mount” and is intended to have “D” shaped washers used where after the alignment is complete, the larger diameter of the washer is inserted into the groove and screws tighten the encoder into place.  When mounting the encoder like this, the flex-mount is completely removed.

The housing of the encoder is made from Nickel coated, conductive carbon fiber that eliminates magnetic interference (EMI) generated by electric motors.  It is available in resolutions up to 2048 PPR or 8,192 quadrature counts per revolution (direct read) with index pulse being a standard feature.

Electrical output can be a Differential Line Driver for noise immunity via a ribbon cable with connector.

The QDI Model 787 encoder is about the diameter of a penny.

There are extended options that are not listed in the QDI online documentation for custom shaft lengths and diameters, making this encoder perfect for potentiometer replacement or other human interface applications.










For more information on the QD787, check out the Spec sheets for both incremental encoder and absolute encoder varieties.

Download the printable versions of the spec sheets for the Absolute Encoder (PDF),  and the Incremental Encoder (PDF)

The Quantum Devices INC. main home page can be reached here.




About Quantum Devices Inc.
Quantum Devices, Inc. (QDI) Barneveld, WI, was established as a Wisconsin corporation in October 1989, as an outgrowth of activities in the general area of optoelectronics. The main goal of QDI is to provide customers with a complete source for all stages of product design and development, starting from concept to a marketable commodity. These products include application specific Silicon Photodiodes, Optical Encoders and Light Emitting Diodes (LED) for commercial, industrial and medical applications. QDI's photodiodes and LED's are used in instrumentation for photosynthesis and photobiological research, biomedical and medical instrumentation for measuring blood sugar levels (glucometer), oxyhemoglobin and pulse rate (pulse oxymeter). One of the most dramatic products developed at QDI was the application of LED lighting systems for use as the light source for Photodynamic Therapy (PDT). Sales of QDI products include both domestic and international markets. Quality and reliability are very important concepts in maintaining our company wide commitment to overall product performance. Quality simply means continuous process improvement. We are committed to continually increasing our product excellence through increased quality and reliability. Quantum Devices, Inc. is ISO 9001 certified and the ISO Standard will provide the guidance for the vital function of maintaining our commitment to constantly improve our product quality. Quantum Devices is now proud to introduce it's new line of rotary encoders. Incorporating QDI's patented sensor technology, our QPhase™ Family of Encoders feature high resolution, increased frequency response and superior reliability over temperature (0 to 120 degrees C). QDI incremental and absolute encoders set a new standard and are backed by a 2 year factory warranty. We invite you to request an evaluation unit, additional information or price quotations. Mission Statement Quantum Devices is dedicated to the principle that light provides the power for all life on earth. We believe the quality, delivery and control of light is essential to the wellness of man and his advancement into the future.

2 Responses to The Versatile QD787 Optical Encoder

  1. Shaokai says:

    From the bottom picture, there seems to be 3 screw holes at the surface of the encoder which is evenly spaced. But it seems that the mounting bracket shown on the upper picture does not fit these screws, so what’s the problem with that? Are there any other kind of mounting bracket which perfectly fit those screws?

    • Hi Shaokai,

      Thanks for taking the time to post a comment.

      The QD787 will have the three hole pattern for all solid shafts. For hollow shafts the QD787 has two machine screws that retain the flex mounting bracket.


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