Rotary Encoders measure the number of
rotations, the rotational angle, and the rotational position. Linear
Encoders are also available to measure linear movement.
What Are Rotary Encoders?
Rotary Encoders are sensors that detect position and speed by converting
rotational mechanical displacements into electrical signals and processing
those signals. Sensors that detect mechanical displacement for straight
lines are referred to as Linear Encoders.
Features of Rotary Encoders
(1) The output is controlled according to the
rotational displacement of the shaft.
Linking to the shaft using a coupling enables direct detection of
rotational displacement.
(2) Returning to the origin is not required at
startup for Absolute Encoders.
With an Absolute Encoder, the rotational angle is output in parallel as an
Absolute value.
(3) The rotation direction can also be detected.
The rotation direction is determined by the output timing of phases A and
B with an Incremental Encoder, and by the code increase or decrease with
an Absolute Encoder.
(4) Choose the optimal Sensor from a wide lineup
of resolutions and output types.
Select the Sensor to match the requirements for precision, cost, and
connected circuits.
Operating Principles
|
Item / Classification |
Features |
Structure and output form |
|
Incremental Encoders
E6J-C
E6A2-C
E6B2-C
E6C2-C
E6C3-C
E6D-C
E6F-C
E6H-C
|
• This type of encoder outputs a pulse
string in response to the amount of rotational displacement of the
shaft. A separate counter counts the number of output pulses to
determine the amount of rotation based on the count.
• To detect the amount of rotation from
a certain input shaft position, the count in the counter is reset at
the reference position and the number of pulses from that position is
added cumulatively by the counter. For this reason, the reference
position can be selected as desired, and the count for the amount of
rotation can be unlimited.
Another important feature is that a circuit can be added to generate
twice or four times the number of pulses for one signal period, for
heightened electrical resolution.*
Also, the phase-Z signal, which is generated once a revolution, can be
used as the origin within a revolution. |
 |
|
* When high resolution is necessary, a
4-multiplier circuit is generally used.
(4x output is obtained by differentiating the rise and fall waveforms
of phase A and phase B, resulting in four times the resolution.) |
When a disk with an optical pattern
revolves along with the shaft, light passing through two slits is
transmitted or blocked accordingly.
The light is converted to electrical currents in the detector
elements, which correspond to each slit, and is output as two square
waves. The two slits are positioned so that the phase difference
between the square wave outputs is 1/4 pitch.
* Even if resolution changes, the number
of phases does not change. |
|
Multi-turn Absolute Encoders
E6C-N
|
• The Absolute data of one revolution
has the same features as normal Absolute Encoders.
The rotation quantity data is output as Absolute data.
• This type of encoder is used when you
wish to change position detection to Absolute data when using an
Incremental Encoder and the Encoder revolves more than once. |
The sensor unit has basically the same
configuration as an Absolute Encoder.
Part of the Absolute signal of one revolution is used to count the
rotation quantity per revolution with the internal counter and output
the multi-turn data as an Absolute code.
 |
|
Absolute Encoders
E6J-A
E6CP-A
E6C3-A
E6F-A |
• This type of encoder outputs in
parallel the rotation angle as an Absolute value in 2ncode.
It therefore has one output for each output code bit, and as the
resolution increases, the value of outputs increases. Rotation
position detection is accomplished by directly reading the output
code.
• When the Encoder is incorporated into
a machine, the zero position of the input revolution shaft is fixed,
and the rotation angle is always output as a digital value with the
zero position as the coordinate origin.
Data is never corrupted by noise, and returning to the zero position
at startup is not necessary.
Furthermore, even when code reading becomes impossible due to
high-speed rotation, correct data can be read when the rotation speed
slows, and correct rotation data can even be read when the power is
restored after a power failure or other interruption in the power
supply. |
 |
|
When a disk with
a pattern rotates, light passing through the slits is transmitted or
blocked according to the pattern. The received light is converted to
electrical currents in the detector elements, takes the form of waves,
and becomes digital signals. |
Selection
Guidelines
1.
Incremental Encoder or Absolute Encoder?
Select a type that is suitable in
terms of the cost vs. capacity, returning (or not) to the origin
at startup, the maximum speed, and noise tolerance.
2. How much resolution is needed?
Select the optimal model in view
of required precision and cost of machine equipment. We
recommend selecting a resolution of from 1/2 to 1/4 of the
precision of the machine with which the Encoder will be used.
3. Dimensions
Also take into consideration the type of shaft that is required
(hollow shaft or regular shaft) in relation to mounting space.
4.
Permitted Shaft Loading
When selecting, take into
consideration how the mounting method affects the load on the
shaft and mechanical life.
5. Maximum Permissible Speed
Base your selection on the maximum
mechanical speed during use.
6. Maximum Response Frequency
Base your selection on the maximum
shaft speed when the device in which the Encoder is used is in
operation.
Maximum response frequency = (Revolutions/60) × Resolution.
There are deviations in the actual signal periods, so the
specifications of the selected model should provide a certain
amount of leeway with respect to the above calculated value.
7. Degree
of Protection
Select the model based on how much
dust, water, and oil there is in the application environment.
Dust only: IP50
Water or oil also present: IP52(f), IP64(f) (water-resistant,
oil-resistant)
Oil present: Oil-proof construction
8.
Startup Torque of Shaft
How much torque does the drive
have?
9. Output
Circuit Type
Select the circuit type based on
the device to be connected, the frequency of the signal,
transmission distance, and noise environment.
For long distance transmission, a line-driver output is
recommended.
Interpreting
Engineering Data
Bearing
Life
Example model: E6B2-C
• This graph shows the
relationship between mechanical life and the load applied to the
shaft.
• The size of the load during
rotation affects the life of the bearings.
Cable Extension
Characteristics
Example model: E6B2-CWZ6C
Measurement Example:
Power supply voltage: 5 VDC
Load resistance: 1 kΩ (Output residual voltage is measured at a
35 mA load current.)
Cable: Special Cable
• This graph shows the effect of
the output waveform if the cable is extended.
• Extending the cable length not
only changes the startup time, but also increases the output
residual voltage.
>> Glossary of Rotary
Encoder
Recommended Products
|
Incremental Rotary Encoder (40-mm
Diameter)
E6B2
General-purpose Encoder with diameter
of 40 mm. |
|
Absolute Rotary
Encoder (40-mm Diameter)
E6C2-A
|
|
Incremental Rotary Encoder (Durable
Type, 50-mm Diameter)
E6C3-C |
|
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