694
Rotary Encoders
4
Rotary Encoders,
Absolute Rotary Encoders,
Standard
4
.1.1
Rotary Encoders,
Absolute Rotary Encoders
for hazardous areas
4
.1.3
Rotary Encoders,
Absolute Rotary Encoders
for safety applications
4
.1.2
Rotary Encoders,
Incremental Rotary Encoders
with pulse outputs
4
.2.1
Rotary Encoders,
Incremental Rotary Encoders,
Sine/Cosine
4
.2.2
Rotary Encoders,
Incremental Rotary Encoders
for hazardous areas
4
.2.4
Rotary Encoders,
Incremental Rotary Encoders
for safety applications
4
.2.3
Rotary Encoders,
Safety Speed Monitor
4
.5
Rotary Encoders,
Cable pulls
4
.3
Rotary Encoders,
Accessories
4
.4
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Consider the General Notes on the Information in the Pepperl+Fuchs Product Catalogs
Pepperl+Fuchs Group
fa-info@de.pepperl-fuchs.com
USA: +1 330 486 0001
fa-info@us.pepperl-fuchs.com
Singapore: +65 6779 9091
fa-info@sg.pepperl-fuchs.com
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Application Notes for Sine/Cosine Rotary
Encoders
Sine/cosine rotary encoders are incremental rotary encoders that pro-
vide analog signals instead of rectangular signals at their outputs stages.
The output voltages of channels A and B have a sine-shaped signal se-
quence. Compared with the digital signals of an incremental rotary en-
coder, such sine and cosine-shaped signals offer a few advantages in
terms of reprocessing in downstream connected control units.
The angular position can be calculated from the number of periods per
revolution and the measured signal periods. The angular speed (w) can
be calculated from the signal frequency. The period duration of the angu-
lar acceleration can also be calculated from the temporal change.
Rotational direction monitoring with sine/cosine
rotary encoders
Both these sine-shaped pulses are electrically phase-shifted by 90°. As
with incremental rotary encoders with rectangular output signals, rota-
tional direction monitoring is also possible for (see graphic).
In the earlier graphic (cw), channel A runs ahead of channel B. This indi-
cates clockwise rotation, whereas ccw indicates counter-clockwise rota-
tion. The direction of rotation is specified on the rotary flange from the
perspective of the viewer.
The actual measurement, more precisely the evaluation (counting) of the
signal periods, takes place in an additional control interface on the plant
side. This could be, for example, a counting and control device (PLC) or
tachometer.
Depending on the type of sine/cosine rotary encoder, channel A or chan-
nel B is the lead channel. Further details are included in the respective
data sheets.
Zero signal
If detection should not be limited to within a revolution, a further signal is
required that appears only once per revolution.This signal (third channel)
is known as a zero signal, channel 0 or spur 0. The zero signal is often
also used as the reference signal.
The reference mark signal for the zero position is issued in analog form. It
has a triangular voltage sequence.
The graphic illustrates the signal sequence of a three-channel sine/co-
sine rotary encoder.
1
V pp
1
V pp
A
B
0
2
V p
t
Pulse multiplication
Pulse multiplication is used to increase the measuring steps or reduce
the output frequency of an incremental rotary encoder. The analog
phase-shifted signals for a sine/cosine rotary encoder can be multiplied
virtually any number of times by linking the channels A and B in an analog
control unit on the plant side.
Correlation between operating speed and output
frequency
See the application notes for incremental rotary encoders.
Properties of sine/cosine rotary encoders
The comparably flat, sine-shaped signal sequence at the outputs of a
sine/cosine rotary encoder results in a number of beneficial features
when compared with incremental rotary encoders with pulse outputs.
These are:
•
Longer available line lengths,
•
Good filtering options compared with line-coupled interfering signals,
•
Excellent suitability for frequency multiplication without the loss of
rotational direction information,
•
Very low phase jitter,
•
High suitability for monitoring extremely long movements.
Application Notes for Absolute Rotary
Encoders
In the case of absolute rotary encoders, both pulses and entire data
words are generated. The detection function that has been developed
especially for this reads the position of the shaft from the code disk. The
data words are transferred in parallel or serial depending on the interface.
Singleturn
In the case of singleturn absolute rotary encoders, one encoder revo-
lution (360°) is divided into a maximum of 65,536 measuring steps (16
bits). After each complete revolution, encryption commences once more
at the start value. The encoder electronics do not recognize how many
revolutions have been completed.
Multiturn
In addition to the encrypted disk that is used with singleturn, a gear is also
integrated for multiturn absolute rotary encoders. This gear is specified
and encrypted in such a way that up to 16,384 revolutions (14 bits) can
be detected. The total resolution is 16 bits (singleturn resolution) in addi-
tion to 14 bits (multiturn resolution), equating to 30 bits. Due to the high
number of measuring steps (over one billion), this type of encoder can
also divide very long linear distances into small measuring steps.
Interfaces
The Pepperl+Fuchs product portfolio incorporates rotary encoders for
the wide range of common interfaces that are available on the market for
absolute rotary encoders:
Parallel interface
The focus of this interface is on rapid data transfer. The position data is
read directly from the gray-coded material measure.
SSI interface
The SSI (Synchronous Serial Interface) interface was developed espe-
cially for transferring output data from an absolute rotary encoder to a
control system.The control unit transmits a start sequence and the abso-
lute rotary encoder responds with a position value.
AS-Interface
Binary sensors are generally networked using AS-Interface in modern
machines and plants. In order to meet real-time requirements, a multi-
slave solution was developed in the form of the AS-Interface rotary en-
coder.
CAN
Pepperl+Fuchs offers CANopen rotary encoders in accordance with
DSP406 (Class 1 and Class 2).
DeviceNet
Device Net rotary encoders add to our range of products. The integrated
interface supports all DeviceNet functions.
PROFIBUS
The absolute rotary encoders in this series comply with the PROFIBUS
profiles for encoders, order no. 3062. They support operation according
to Class 1 and Class 2.
Rotary Encoders
