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Typical Usage
An encoder is a device (transducer) that is used to convert rotary
or linear motion into useful information. The primary parameters
determined are speed, rate, velocity, distance, position, or direction.
A typical application will use one or more of these parameters as
feedback to the controller in a motion control system.
EPC's rugged and reliable encoders are particularly suited to the
most challenging applications in process and machine control, motor
feedback, factory automation, robotics, web tensioning, etc. In
addition to these applications, rotary optical encoders can also
provide electronic commutation in brushless servo systems.
| Motor feedback is the most common way that
rotary encoders are used. In this type of application, an encoder
is either mounted directly to the motor, or indirectly using
a measuring wheel or chain-and-sprocket arrangement. The parameter
of interest is primarily the speed of the motor. |
| Web tensioning is an application in which
the encoder is not usually mounted to the drive motor, but to
one of the tensioning arm rollers. Any unevenness in the speed
of this roller indicates that proper web tension is not being
maintained and must be adjusted. The rotating speed of the tensioning
roller is fed back to the controller, which then adjusts the
drive motor so that web material is kept at an even tension. |
| Cut-to-Length is a very practical application
of an encoder combined with simple mathematics. If, for example,
a system were to be designed with a roller that is exactly one
foot in circumference, the roller would feed one foot of material
for every revolution of the roller. An encoder mounted to the
roller would reflect this situation and could tell a controller
how much material had been fed through the roller. The resolution
of the encoder would also directly reflect the accuracy of the
cut. In the above example, 96 PPR would yield cuts to an 1/8"
accuracy. |
| Elevators are just one example where encoders
can perform a dual role. They can determine the position of
the elevator through a mathematical calculation similar to the
above, and they can determine the speed of travel of the elevator. |
| Registration Mark Timing uses encoders
to determine the position of a unit relative to a known point,
and then to determine the unit's speed relative to that mark.
Radar antenna rotation is a good example of this type of application. |
| In Backstop Gauging the encoder is used
to make sure that the unit, typically a machine tool, does not
exceed a preset position or direction of travel. Very often,
this is combined with a determination of the speed of travel
of the table, tool head, or similar component. |
| Filling applications is just one example
where Table Positioning is critical since the item being filled
must arrive at filling tube at the same time the fluid control
is turned on. |
| Conveying is another common industry where
encoders are widely used. They may be attached to the motor,
to intermediate axle shafts, or to both. Encoders are an especially
effective feedback device where the positioning and/or speed
of multi-element conveying systems must be carefully coordinated. |
| Spooling (sometimes referred to as Level
Wind) is another application where encoders can prove invaluable.
Not only is it necessary that the speed of the supply and take-up
reels be kept in proper relation to each other, but the amount
of material being spooled must also often be tracked. |
| Electronics is just one industry that widely
uses encoders in Pick and Place applications. Here many of the
capabilities of encoders (rate, position, speed, velocity) can
often be found combined in a single system. |
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