Posts for May 2019

Encoders 008 - The Strange History of the Industries from which Encoders Evolved

What do these have in common?

What do an organ, a black widow spider, and a scale have in common?

Classic Ultrasound Machine

It has always been intriguing to me how companies came into existence. US Digital's founding is an exclamation to the saying - "necessity is the mother of invention". David Madore, the founder of US Digital, worked at the time as a design engineer for a medical ultrasound imaging company. The equipment had many knobs on the front panel for potentiometers. The company wanted to upgrade the design to use optical encoders to improve operation. In doing research they could not find a good source suitable for the application. The ones they found were overpriced, had long lead times and poor specifications. In 1980, David Madore, made his first encoder to meet this need. And as they say, the rest is history.

Parlor Organ

BEI's history dates back to the 1800's. Many of us have heard of Baldwin pianos or organs but are unaware of how they fit in with encoders. Dwight Hamilton Baldwin was a minister and a singing teacher in schools who also opened a music store in Cincinnati, Ohio in 1862. Instead of just distributing the keyboard instruments, he set out to make "the best piano that could be built". World War II interrupted their operation as the company participated in making wings and other aircraft parts. A more detailed account of their history is available if you are interested.

Glass Disks

After the war, Baldwin started using electronics in the development of keyboard instruments. The goal was to use this technology in an organ to replicate the sound of pipe organs in European cathedrals. The engineers at Baldwin came up with a way to use optically encoded glass discs to reproduce the organ tones. The codewheel transcribed the original organ tones into etched glass - in opaque and transparent segments so that when the disk turned, it created an alternating pattern of light and dark. Photodiodes were used to translate this into an electronic signal (sound familiar?) which was processed and amplified to create the tones and harmonics desired.

Sidebar - this development by Baldwin was not the first use of photo-electricity with a spinning glass disk to create musical tones. This was done as early as the 1920's in France, Austria, Russia, Germany, and the USA.

In 1951 the U.S. Army Signal Corp contracted with Baldwin to develop optical encoders, realizing that the company's technology could help in the pointing and tracking for radar antennas. In 1955 Baldwin made their first experimental optical encoder. In 1962, Baldwin's research resulted in an 18-bit optical encoder which was the first optical encoder used in space. The following year, they produced the first optical encoder with an LED light source which was used in space as was highlighted in our post, "Who Made the First Optical Encoder". That same year the electronics division was incorporated as Baldwin Electronics, Inc., hence the name, BEI.


The Gurley enterprise was established in 1845 but changed to W. & L. E. Gurley in 1852 as the brothers, William and Lewis, both engineering graduates of Prensselaer Polytechnic Institute in New York teamed up to create products with technical innovations. The Gurley brothers had many different interests but most related in one way or another to measuring things - from electrical current to pressure, to weights and distances and angles. In their factory the brothers created different departments, with each department making different components and then final assembly taking place in still another department after all components had been made.

Crosshair Drawings

The area of technology by Gurley which is of most interest to those of us in the encoder field is the surveying field and their designing of theodolites - an optical instrument used for measuring angles. The crosshairs used in the late 1800's for these surveying tools was the spider web filament from a black widow spider. The spider web filament was impregnated into the glass of their surveying instrument eyepieces. Gurley and other surveying equipment companies, actually had black widow spiders in their employment to provide them with the material they needed to create the crosshairs.


This technology was also used in the war effort in both world wars. One of the numerous industries developed in the US following the bombing of Pearl Harbor was the special defense plants or spider ranches supplying the spider silk for everything from bomber sights to periscopes and telescopes. The next time you think about complaining about your coworker, remember to be thankful it isn't a black widow spider.

Gurley was an early adopter of photolithography to transition from the use of spider webs. This new method provided for chrome patterns on the glass which not only was a superior method but provided a relief from the literally toxic work environment. This technology was offered as a service to others and in fact, according to Martin Gordinier of Gurley, they created the first encoder disk for Dr. Gray - famously known for the development of the Gray code used on encoder disks. After selling encoder disks to many firms, Gurley started producing their own encoders in the 1950's.

Etching examples

Wilhelm Heidenhain founded his company in 1889. It began as a metal etching factory. The company etched templates, signs, graduations, and scales. Heidenhain's enterprise was destroyed in World War II and the Dr. Johannes Heidenhain Company was founded in Traunreut by Wilhelm Heidenhain's son in 1948.


One revolutionary advancement was the development of the diadur process in 1950 which enabled them to apply very fine structures of chromium on glass. In 1952 Heidenhain used the diadur process to create optical position measuring devices for machine tools. That same year they introduced their first optical linear and angle encoders for machine tools. It was in 1961 that Heidenhain produced its first photoelectric incremental rotary encoder for position feedback (10,000 lines).

It is my goal to make this blog as informative, engaging and as accurate as possible. If you ever have some additional or contrary information, please contact me directly and I will be glad to make any appropriate corrections in a future post. Previous Post

Organ picture source -
Black widow spider image -
Source for scale picture -
Ultrasound machine image -
Glass disk imagery -
Theodolite image -
Cross hair imagery source -
Source for bombsight image -
Classic Baldwin Organ photo -

Written by Steve Mathis
Director of Customer Relations & Marketing

"My goal at US Digital is to work with the excellent teams here to contribute to the success of our customers by eliminating pain points and making it easy for them to do business with us."

Encoders 007 - Encoders: Mechanical Configurations

US Digital Product Family

We will continue in this post going through the various classification of encoders which were identified in my earlier post.

Mechanical Configurations

Mechanical configurations include differences based on whether the encoder comes with a shaft or will be installed onto an existing shaft. There are also different configurations based on the size of the motor, the required IP rating, and other environmental conditions.

Mechanical configurations

Motor feedback encoders may contain their own bearings, or they may use an existing bearing set such as that found on the tail shaft of a servo motor. The best configuration option to use is a function of the stability of the shaft/bearings to which the encoder is attached. Feedback encoders with bearings are typically used when the application shaft has a significant amount of axial or radial run out (eccentricity or vibration). The use of a shafted encoder with a motor will require some sort of flexible member, either a flexible shaft coupling or flexible body mount, to allow mechanical compliance with the application shaft operating irregularities.

Kit Encoder example

Modular encoders, also referred to as encoder kits, don’t contain their own internal shaft. They are assembled from components supplied by the encoder manufacturer and are designed to be attached to the tail shaft and end bell of the motor. These encoders rely on a mechanically stable motor shaft, as the shaft is responsible for holding the encoder’s internal rotating code wheel in a precise location relative to the encoder’s sensing module. For these applications, motor manufacturers put a considerable amount of effort in designing high-performance motors with very stable shaft/bearing assemblies. Because the modular design does not add the expense of the extra set of bearings that a motor feedback encoder does, modular encoders offer one of the most cost effective feedback solutions.

Modular encoders

When using a kit style encoder, another mechanical consideration is the size of the motor. Most encoder manufacturers supply a motor/encoder compatibility chart based on the motor size. It is recommended to use such a chart, like the one below, to help identify the appropriate encoder model.

Spec table sample
IP65 Rated encoder

Another mechanical configuration relates to environmental conditions. If the encoder will be installed in an environment that is subject to excessive dust and/or moisture, encoders are available with various IP ratings to meet those requirements. Magnetic and capacitive encoders would also be a potential candidate to meet some environmental concerns.

Modular encoders

Finally, there are many applications of encoders where they are inherently protected from physical contact. However, other encoders are located where they might be contacted by a person or object, therefore, requiring more physical protection. The above housing is machined from solid aluminum to provide the kind of protection needed in such an application.


If you are afraid of spiders, you might want to skip our next post which is scheduled for May 28th.

It is my goal to make this blog as informative, engaging and as accurate as possible. If you ever have some additional or contrary information, please contact me directly and I will be glad to make any appropriate corrections in a future post. Previous Post

Written by Steve Mathis
Director of Customer Relations & Marketing

"My goal at US Digital is to work with the excellent teams here to contribute to the success of our customers by eliminating pain points and making it easy for them to do business with us."