INCREMENTAL ENCODER INTERFACE
Incremental rotary encoders generate an output signal each time the shaft rotates a
certain angle. The number of signals (pulses) per turn defines the resolution of the
device. The incremental encoder does not output an absolute position, which makes the
internal components of the encoder much simpler and more economical.
Besides position tracking, incremental encoders are often used to determine velocity.
The position in relation to the starting point can be calculated by counting the number of
pulses. The velocity can be retrieved by dividing the number of pulses by the measured
time interval
BEI type GHU 930 2048 009 encoder with output signal in HTL & TTL working
principle.docx.
TYPE GHU 930//
5G 29 //2048//G5R// **D4**
as shown in the data sheet.
. ORDERING REFERENCE (Contact the factory for special versions, ex: shaft size, resolution, connection)
Shaft IP Supply Output stage Output signals Resolution Connection
Orientation
Reduction
hub
Anti-rotation
GHU9 X
30:
30mm
Reduction
hub
available
01:
IP66
Digital signals: 2G2, 5G2, 5G5
2048
max
G6: M23 12
pins CW
G8 : M23 12
pins CCW
R : radial
** :
No
reduction
hub
U2 :
Reduction
hub
DW**:
9445/045
2:5Vdc
5:11 to
30Vdc
G2: driver 5Vdc
RS422
G5 : push-pull
9: AA/ BB/ ZZ/
Sine-wave signals: 2WT, 5WT
GP: PUR cable
12 wires
G3: PVC
cable 8 wires
Example :
R020 : radial
cable 2m
2: 5Vdc
5:11 to
30Vdc
WT: sine 1Vpp N: SS/ CC/ ZZ/
Ex: GHU 9X 30 / 01 / 5 G2 9 // 01024 // GP R050 // ** DW**
Made in France
Changes possible without further notice - Version 140604
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Basic Principle Incremental Encoder
Incremental rotary encoders provide a serial output signal on a single transmission line.
One sensor must be connected to one controller.
An incremental encoder has at least 1 output signal “A” or typically 2 output signals,
called “A” and “B”. These 2 signals are set up with a 90° offset, which is required for the
detection of the encoder’s rotation. By turning the encoder clockwise, the “A” pulse is
rising 90° ahead of the “B” pulse, by turning the shaft counterclockwise, the “B” pulse is
rising ahead of the “A” pulse.
Additionally some incremental encoders output a “Z” signal. Once every rotation, this Z
signal is rising for typically 90°, on the exact same position. This can be used as an
accurate reference point.
Some incremental encoders also have additional differential signals, called “/A”, “/B”
and “/Z”. These signals are inverted “A”, “B” and “Z” signals. Controllers can compare
each pair (“A” must be equal to inverted “/A”) to ensure that there is no error during the
transmission.
Additionally the transmission sensitivity is improved by transmitting the differential
signals through a twisted pair cable.
Typical pulse diagram
Encoder Characteristics
Pulses per revolution (PPR):
An incremental rotary encoder outputs a certain amount of Pulses per Revolution. The
higher this PPR number, the smaller the angle between each pulse. This PPR number
is fixed for ordinary incremental encoders. Programmable incremental encoders can
adjust this value to a desired number by a software change.
Output drivers:
Today most incremental encoders have a Push-Pull (HTL) or RS422 (TTL) output
driver, these have replaced most of the older output circuits like Open Collector NPN,
Open Collector PNP, Voltage Output.
A) Push-Pull (HTL)
Push-Pull (HTL) circuits, also known as Totem Pole, provide a signal level which
corresponds to the applied supply voltage. The supply voltage typically ranges from 8 to
30 VDC.
With proper connections you can use the Push Pull interface to replace true open
collector circuits by using an external diode connected in a way to limit the direction of
the current for
B) RS422 (TTL)
RS422 (TTL) circuits provide a constant 5 V signal level that is not dependent on the
supply voltage. Two supply voltage ranges can be selected: From 4.75 to 5.5 VDC (can
be used to replace open collector output drivers) or from 8 to 30 VDC. Using differential
signals the output fully complies to the RS422 standard.
The differential outputs have the highest frequency response capability and the best
noise immunity. To ensure this the receiver should also be a differential.
Replacement of Older Output Drivers
1) PNP open collector replacement (Current source)
2) NPN open collector replacement (Current Sink)
Programmable Incremental Encoder
Non programmable incremental encoders can only be configured at the factory to the
customer’s specs. However, if application requirements change, with programmable
incremental encoder it is very simple to adjust some key characteristics. By changing
certain parameters in the software with the help of an external configuration tool
(UBIFAST Configuration Tool), customers can modify the
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Incremental
INCREMENTAL ENCODER INTERFACE
Incremental rotary encoders generate an output signal each time the shaft rotates a
certain angle. The number of signals (pulses) per turn defines the resolution of the
device. The incremental encoder does not output an absolute position, which makes the
internal components of the encoder much simpler and more economical.
Besides position tracking, incremental encoders are often used to determine velocity.
The position in relation to the starting point can be calculated by counting the number of
pulses. The velocity can be retrieved by dividing the number of pulses by the measured
time interval.
Basic Principle Incremental Encoder
Incremental rotary encoders provide a serial output signal on a single transmission line.
One sensor must be connected to one controller.
An incremental encoder has at least 1 output signal “A” or typically 2 output signals,
called “A” and “B”. These 2 signals are set up with a 90° offset, which is required for the
detection of the encoder’s rotation. By turning the encoder clockwise, the “A” pulse is
rising 90° ahead of the “B” pulse, by turning the shaft counterclockwise, the “B” pulse is
rising ahead of the “A” pulse.
Additionally some incremental encoders output a “Z” signal. Once every rotation, this Z
signal is rising for typically 90°, on the exact same position. This can be used as an
accurate reference point.
Some incremental encoders also have additional differential signals, called “/A”, “/B”
and “/Z”. These signals are inverted “A”, “B” and “Z” signals. Controllers can compare
each pair (“A” must be equal to inverted “/A”) to ensure that there is no error during the
transmission.
Additionally the transmission sensitivity is improved by transmitting the differential
signals through a twisted pair cable.
Typical pulse diagram
Encoder Characteristics
Pulses per revolution (PPR):
An incremental rotary encoder outputs a certain amount of Pulses per Revolution. The
higher this PPR number, the smaller the angle between each pulse. This PPR number
is fixed for ordinary incremental encoders. Programmable incremental encoders can
adjust this value to a desired number by a software change.
Output drivers:
Today most incremental encoders have a Push-Pull (HTL) or RS422 (TTL) output
driver, these have replaced most of the older output circuits like Open Collector NPN,
Open Collector PNP, Voltage Output.
A) Push-Pull (HTL)
Push-Pull (HTL) circuits, also known as Totem Pole, provide a signal level which
corresponds to the applied supply voltage. The supply voltage typically ranges from 8 to
30 VDC.
With proper connections you can use the Push Pull interface to replace true open
collector circuits by using an external diode connected in a way to limit the direction of
the current for
B) RS422 (TTL)
RS422 (TTL) circuits provide a constant 5 V signal level that is not dependent on the
supply voltage. Two supply voltage ranges can be selected: From 4.75 to 5.5 VDC (can
be used to replace open collector output drivers) or from 8 to 30 VDC. Using differential
signals the output fully complies to the RS422 standard.
The differential outputs have the highest frequency response capability and the best
noise immunity. To ensure this the receiver should also be a differential.
Replacement of Older Output Drivers
1) PNP open collector replacement (Current source)
2) NPN open collector replacement (Current Sink)
Programmable Incremental Encoder
Non programmable incremental encoders can only be configured at the factory to the
customer’s specs. However, if application requirements change, with programmable
incremental encoder it is very simple to adjust some key characteristics. By changing
certain parameters in the software with the help of an external configuration tool
(UBIFAST Configuration Tool), customers can modify the
Incremental output driver – set the output driver to Push-Pull (HTL) or RS422 (TTL)
Pulses per revolution – program the PPR to a defined value
Incremental pulse direction – choose “A before B“ or “B before A“
Device programmability is very significant for distributors, system integrators or machine
builders since it helps them reduce inventories. Now, they can hold a relatively small
stock of ‘standard’ models and set them up for specific applications on an as-needed
basis.
Specifications
Voltage Output Levels:
A logic gate interprets certain input voltages as high (logic 1) or low (logic 0).
TTL (transistor-transistor-logic): A signal above 2 V is interpreted as logic 1 and a signal
less than 0.8 V is interpreted as logic 0. The output voltage ranges between 0-5 V.
HTL (high-threshold-logic): A signal above 3 V is a logic 1 and a signal less than 1 V is
a logic 0. The high output signal level is dependent from the supply voltage. Because of
the higher voltage difference between logic 0 and 1, the HTL logic is more immune to
interference and more resistant against electrical noise.
Logic Signal Level Supply Voltage
Output Voltage
TTL
HTL
High
Low
High
Low
4.75-30 V
4.75-30 V
4.75-9 V
9-30 V
4.75-30 V
min 3 V
max 0.5 V
min 3 V
min Supply Voltage - 3 V
max 0.5 V
Table 1: Output levels of POSITAL incremental rotary encoders (I=50 mA per channel)
Electrical and Mechanical Degree:
Mechanical degree is the actual rotation of the shaft in degrees. Electrical degree is
used for electrical signals. The required time for completing one alternating
voltage/current cycle is defined as 360 electrical degrees (el°). For incremental
encoders, one cycle is equal to one complete pulse. With a given PPR the electrical
degree can be converted to mechanical degree for any incremental encoder.
Quadrature:
Every 90 el° the incremental encoder outputs a rising or falling edge on the “A” or “B”
output that can be interpreted as a count. If an encoder outputs 1000 PPR, a counter
can interpret 4000 counts (4 counts each pulse).
Phase Angle:
The phase angle states the length between 2 edges, given in el°. This parameter is
typically specified with a defined constant phase angle value and phase angle error
(also called quadrature error).
Accuracy (DNL):
The DNL accuracy is the phase angle error as an absolute value given in (mechanical)
degrees.
Accuracy (INL):
An incremental encoder outputs a defined amount of pulses per revolution, so that
every pulse is expected to be on a defined mechanical position. The maximum deviation
between this ideal position and the actual position is called integral non linearity (INL).
The INL accuracy is an important value if the incremental encoder is used for
positioning tasks.
Duty Cycle:
The duty cycle describes the ratio between “high” time to “low” time of an incremental
encoder. Typically this ratio is 50/50, which is equivalent to 180 el° high and 180 el° low.
The performance of magnetic incremental encoders increases with higher PPR settings
and higher rotation speeds (RPM). This is in contrast to optical encoders where the
performance decreases. The DNL and INL accuracy that are stated in our datasheets
are worst case values, a better performance can be expected for higher PPR and RPM.
Frequency Response:
This is the maximum frequency that the encoder is able to output via the output lines.
For example, the frequency of a 200 PPR encoder that rotates at 600 RPM is 2000 Hz
Device programmability is very significant for distributors, system integrators or machine
builders since it helps them reduce inventories. Now, they can hold a relatively small
stock of ‘standard’ models and set them up for specific applications on an as-needed
basis.
Specifications
Voltage Output Levels:
A logic gate interprets certain input voltages as high (logic 1) or low (logic 0).
TTL (transistor-transistor-logic): A signal above 2 V is interpreted as logic 1 and a signal
less than 0.8 V is interpreted as logic 0. The output voltage ranges between 0-5 V.
HTL (high-threshold-logic): A signal above 3 V is a logic 1 and a signal less than 1 V is
a logic 0. The high output signal level is dependent from the supply voltage. Because of
the higher voltage difference between logic 0 and 1, the HTL logic is more immune to
interference and more resistant against electrical noise.
Logic
Signal Level
Supply Voltage
Output Voltage
TTL
High
Low
4.75-30 V
4.75-30 V
min 3 V
max 0.5 V
HTL
High
Low
4.75-9 V
9-30 V
4.75-30 V
min 3 V
min Supply Voltage - 3 V
max 0.5 V
Table 1: Output levels of POSITAL incremental rotary encoders (I=50 mA per
channel)
Electrical and Mechanical Degree:
Mechanical degree is the actual rotation of the shaft in degrees. Electrical degree is
used for electrical signals. The required time for completing one alternating
voltage/current cycle is defined as 360 electrical degrees (el°). For incremental
encoders, one cycle is equal to one complete pulse. With a given PPR the electrical
degree can be converted to mechanical degree for any incremental encoder.
Quadrature:
Every 90 el° the incremental encoder outputs a rising or falling edge on the “A” or “B”
output that can be interpreted as a count. If an encoder outputs 1000 PPR, a counter
can interpret 4000 counts (4 counts each pulse).
Phase Angle:
The phase angle states the length between 2 edges, given in el°. This parameter is
typically specified with a defined constant phase angle value and phase angle error
(also called quadrature error).
Accuracy (DNL):
The DNL accuracy is the phase angle error as an absolute value given in (mechanical)
degrees.
Accuracy (INL):
An incremental encoder outputs a defined amount of pulses per revolution, so that
every pulse is expected to be on a defined mechanical position. The maximum deviation
between this ideal position and the actual position is called integral non linearity (INL).
The INL accuracy is an important value if the incremental encoder is used for
positioning tasks.
Duty Cycle:
The duty cycle describes the ratio between “high” time to “low” time of an incremental
encoder. Typically this ratio is 50/50, which is equivalent to 180 el° high and 180 el° low.
The performance of magnetic incremental encoders increases with higher PPR settings
and higher rotation speeds (RPM). This is in contrast to optical encoders where the
performance decreases. The DNL and INL accuracy that are stated in our datasheets
are worst case values, a better performance can be expected for higher PPR and RPM.
Frequency Response:
This is the maximum frequency that the encoder is able to output via the output lines.
For example, the frequency of a 200 PPR encoder that rotates at 600 RPM is 2000 Hz