KNOWLEDGE BASE
Glossary
A
A Quad B
A Quad B refers to the set of output quadrature signals from an incremental quadrature encoder to indicate speed and direction, including complements: A, A NOT, B, B NOT (, , , ). Most Avtron encoders offer A Quad B output at no extra cost. For more information on quadrature – Wikipedia: http://en.wikipedia.org/wiki/Quadrature_phase
Absolute Encoder
Absolute indicates the position of the rotor or shaft referenced to a fixed starting position. If power is turned off and then on, the encoder recalls the position correctly. It may output the position information on a set of output wires (parallel), or it may output the absolute position using a communications bus, such as Profibus or DeviceNet. Absolute encoders can be single-turn or multi-turn. For more information – Wikipedia: http://en.wikipedia.org/wiki/Rotary_encoder
Absolute Position
Absolute position indicates the position of a rotor or shaft referenced to a fixed starting position. Resolvers and absolute encoders can provide absolute position feedback.
Accuracy
Encoder accuracy is the ability of or limit to the encoder to repeat the exact same signals, given the exact same mechanical position. Accuracy and resolution may be independent – an encoder can have higher accuracy than resolution, and vice versa. Avtron incremental encoders are typically accuracy rated at +/-1 count of their resolution; Avtron absolute encoder accuracy varies by model.
AN-DC
AN-DC was an analog tachogenerator manufactured by General Electric, 8.5″ NEMA FC face mount. It is now obsolete. It may be replaced by an Avtron AV850 encoder combined with a K661 converter solution.
AN-DG
AN-DG was a digital encoder sold by General Electric, 8.5″ NEMA FC face mount. It is now obsolete. It may be directly replaced by an Avtron AV850 encoder.
Analog Tachogenerators
Also known as DC tachogenerators, analog tachogenerators are small DC generators that output a voltage in proportion to speed. They cannot indicate position, only speed and direction of rotation. A common mounting style of analog tachogenerator was the General Electric BC42 and BC46 Series with NEMA 56C foot or face mount, and the smaller 5PY flange mount unit. Analog tachogenerators can be replaced with modern digital encoders. Avtron offers a complete retrofit package using the existing flange adapter and coupling already on the motor and a Frequency-to-Voltage Converter like the Avtron K661, which resides in the drive cabinet.
Anti-Rotation Arm
A device used to prevent hollow shaft encoders from spinning with the shaft rotation. It is also called a tether or a torque arm. To prevent encoder bearing damage, anti-rotation arms are very flexible and permit all movements, including axial shaft movement but not rotation.
ATEX
ATEX is a directive used worldwide for equipment, including encoders, to be used around or in explosive atmospheres. ATEX certified equipment is NOT necessarily interchangeable with US-based UL Class/Division or Class/Zone rated equipment, nor IECEx rated equipment. ATEX is an alternative and different system. Review our full line of Avtron Explosion Protected, ATEX certified encoders, including M6, M6C and XR models.
Axial Shaft Movement
Motor shaft movement in or out, relative to the ends of the motor. Often motors that use roller or sleeve bearing construction have more axial shaft movement. Most Avtron modular encoders tolerate +/- 0.050″ of axial movement maximum. Use hollow shaft encoders for high axial movement motor styles, such as MD motors. Most competitors’ modular encoders tolerate much less axial movement than Avtron products.
B
B10 Flange
- A flange used on European IEC frame motors to mount encoders (analogous to the NEMA 56C flange). Six holes are located on a 100mm bolt circle, surrounding an 85mm flange. Avtron offers both the AV44 and AV45 heavy-duty encoders which directly fit the B10 flange, as well as the AV115 bearingless encoder which can be adapted to the B10 flange.
Bayonet Connector
This is a 10 pin military style connector used for Avtron encoders. It includes a set of locking pins and slots instead of the threaded mating system on most MS connectors. It is also known as “Mini-Twist-Lock”, “MS Mini” and “Baldor connector”.
BC42
An analog tachogenerator manufactured by General Electric, part number 5BC42xxxxx, NEMA 56C face or foot mount, coupled. It is now obsolete. It may be replaced by an Avtron encoder combined with a K661 converter solution.
BC46
An analog tachogenerator manufactured by General Electric, part number 5BC46xxxxx, NEMA 56C face or foot mount, coupled. It is now obsolete. It may be replaced by an Avtron encoder combined with a K661 converter solution.
BC66
A heavy duty analog tachogenerator manufactured by General Electric, part number 5BC66xxxxx, NEMA 56C face or foot mount, coupled. It is now obsolete. It may be replaced by an Avtron encoder combined with a K661 converter solution.
Bearingless
These encoders use the bearings of the motor or machine, eliminating a huge source of failure in encoders. Also known as modular and sandwich encoders.
Bus
A communications (field) bus is used to carry absolute encoder signals to the control system. It may do so automatically on a clock signal input to the encoder (SSI), or in response to a message (ex: Profibus, DeviceNet). For more information on fieldbuses – Wikipedia: http://en.wikipedia.org/wiki/Fieldbus
C
C-Face
A machined flange or elevated/recessed face provided on motors for mounting accessories. Typically provided on the drive end for gearbox/load mounting, C-faces may also be provided on the non-drive end for mounting encoders, brakes, and other accessories.
Cam Screw Rotor™
A Cam Screw Rotor™ eliminates the problems associated with slipping rotors of other types; it uses two cam (eccentric) head screws. The screws are preloaded into the rotor; simply rotate them (approximately 90°-180°) to fully engage the shaft (4-6 ft-lbs) using a standard hex (Allen) wrench. Cam Screw Rotors™ are available on AV850, AV56, AV67, AV85 and AV115 THIN-LINE II™ encoders. Cam Screw Rotor™ Patent #7,485,997. Cam Screw Rotor™ is a trademark of Avtron.
CANopen
CANopen is a fieldbus used by Avtron absolute encoders to report position and speed to a controller. CANopen uses a 4 wire main bus + drop wiring system (CAN). CANopen is hardware-identical to DeviceNet and J1939, but the encoder messages sent are different. For encoder communications, SSI, Ethernet or Profibus may be faster than CANopen. For more information on CANopen – Wikipedia: http://en.wikipedia.org/wiki/Canopen
Complements
Also known as complementary outputs. To ensure that signal noise does not cause errors between the encoder and the controller, many encoders output signals that are driven in exactly opposite directions: when A goes high, A NOT goes low; when A goes low, A NOT goes high. Controllers which see a transition in A, but not in the A NOT signal, would report a quadrature error.
Contamination
Also known as contaminants, such as water, dirt, dust, oil and other compounds which enter an encoder through seal failure and can cause optical errors. If the contamination is abrasive, it can also cause bearing failures in the encoder. Modular encoders are very resistant to contamination as they use magnetoresistive sensors and have no bearings.
Coupled/Coupling
Refers to a flexible device that is used to link a solid shaft encoder to the shaft to be monitored. Avtron strongly recommends isolated, flexible disk-style couplings in heavy-duty applications to maximize encoder bearing life. For light mill duty applications, flexible helical couplings are a great option. If there’s a large amount of axial shaft movement or misalignment, shift to magnetic couplings.
Cycles Per Revolution (CPR)
This is the sine-cosine encoder equivalent to PPR. It indicates the number of sine waves output per revolution, and does not count the cosine waves. Some vendors also use CPR as an equivalent to PPR for digital incremental encoders.
D
DC Tachogenerators
Also known as analog tachogenerators. Small DC generators that output a voltage in proportion to speed. They cannot indicate position, only speed and direction of rotation. A common mounting style of analog tachogenerator was the General Electric BC42 and BC46 Series with NEMA 56C foot or face mount, and the smaller 5PY flange mount unit. Analog tachogenerators can be replaced with modern digital encoders. Avtron offers a complete retrofit package using the existing flange adapter and coupling already on the motor and a Frequency-to-Voltage Converter like the Avtron K661, which resides in the drive cabinet.
DeviceNet
DeviceNet is a fieldbus used by Avtron absolute encoders to report position and speed to a controller. DeviceNet uses a 4 wire main bus + drop wiring system (CAN). DeviceNet is hardware-identical to CANopen and J1939, but the encoder messages sent are different. For encoder communications, SSI, Ethernet or Profibus may be faster than DeviceNet. For more information on DeviceNet – Wikipedia: http://en.wikipedia.org/wiki/Devicenet
E
EDS
EDS files are text files used to configure the DeviceNet scanner to receive information from each device (bytes/words/meaning). Avtron absolute encoders use DeviceNet EDS files to enable the user to add Avtron absolute encoders to their bus(es). Contact Nidec Industrial Solutions for EDS files for your Avtron encoder.
Encoder
A device which indicates position and speed via a set of digital outputs. Incremental encoders output quadrature (A Quad B) signals, and may add a marker pulse once per revolution. Absolute encoders typically indicate position via a digital message, a set of parallel outputs or analog values.
EnDat
EnDat is a proprietary protocol used for some absolute encoders. EnDat encoders are only manufactured by one company, eliminating competition. Most controllers which support EnDat also support SSI, which is an open protocol to all vendors and is used by Avtron absolute encoders.
Ethernet/IP
Ethernet/IP is an Ethernet-based fieldbus used by Avtron absolute encoders to communicate with a controller. For more information about Ethernet/IP – Wikipedia: http://en.wikipedia.org/wiki/EtherNet/IP
Explosion Protected
Also known as Flameproof, Explosion Protected equipment has additional protection/safety enhancements for use in explosive atmospheres. Explosion Protected devices may be placed directly into hazardous areas within their nameplate rating. No additional equipment is required if installation instructions are followed properly. By comparison, Intrinsically Safe devices may require the use of additional, external protection/current limiting devices outside of the hazardous area. Avtron offers hollow shaft M6C Explosion Protected encoders.
F
Face or Flange Mount
A machined surface (NEMA 56C, NEMA FC) on the non-drive end of the motor is used to face mount a bearingless or pancake encoder such as an Avtron AV56 THIN-LINE II™ encoder. Solid shaft, coupled tachometers are flange mounted using adapters, also called flowerpots.
False Pulses
Pulses output by the encoder when no pulses should be output. They are often caused by contamination on optical disks that is misread as a line on the optical disk.
Fieldbus
A fieldbus (communications wiring hardware and software standard) is used to carry absolute encoder signals to the control system. It may do so automatically on a clock signal input to the encoder (SSI), or in response to a message (ex: Profibus, DeviceNet). For more information on fieldbuses – Wikipedia: http://en.wikipedia.org/wiki/Fieldbus
Flameproof
Also known as Explosion Protected, flameproof encoders have additional protection/safety enhancements for use in explosive atmospheres. Flameproof encoders may be placed directly into hazardous areas within their nameplate rating. No additional equipment is required if installation instructions are followed properly. By comparison,
Intrinsically Safe encoders may require the use of additional, external protection/current limiting devices outside of the hazardous area. Avtron offers hollow shaft M6C Flameproof encoders.
Flange Adapter
A flange adapter provides the NEMA 56C motor mounting face and properly locates the encoder shaft. The encoder shaft and motor shaft are then connected using a flexible coupling (Drawing “A”). Often flange adapters can be eliminated by directly mounting a modular encoder such as an Avtron AV125, AV850, AV56, AV67, AV85 or AV115 unit on the motor flange (Drawing “B”).
Flowerpot
A term for the flange adapter used to mount a solid shaft encoder to a motor face.
Foot Mount
Foot mount encoders are bolted to a motor foot, shelf or other nearby location. The solid shaft encoder is coupled to the shaft to be monitored. Modern Avtron encoders (AV485) require a separate foot mounting bracket. To eliminate coupling and alignment maintenance issues, foot mounting installations can be upgraded to a hollow shaft encoder such as the AV685.
Functional Safety
Functional safety is the part of the overall safety of a system or piece of equipment that depends on automatic protection operating correctly in response to its inputs or failure in a predictable manner (fail-safe). The Avtron SV850 Encoder features SIL 2 rating and a no-bearing design.
Avtron SV850 Encoders are suitable for:
SAR – Safe Acceleration Range
SBC – Safe Brake Control
SDI – Safe Direction Indication
SLA – Safe Limited Acceleration
SLI – Safe Limited Increment
SLS – Safe Limited Speed
SOS – Safe Operating Stop
SSM – Safe Speed Monitor
SSR – Safe Speed Range
SS1 – Safe Stop 1
SS2 – Safe Stop 2
STO – Safe Torque Off
G
GSD
GSD files are text files used in Profibus configuration to instruct the master/scanner device of the information coming from each device (bytes/words/meanings). The user of Avtron encoders downloads the file, then adds it to the configuration software. Then Avtron absolute encoders can be added to the bus configuration. Avtron absolute encoder GSD files are found in the Documents tab for each encoder, on the product page.
H
Heavy Mill Duty
Heavy mill duty encoders are designed to withstand temperature cycling, extreme temperatures, contaminants, bearing loads and physical force.
Hiperface
Hiperface is a proprietary encoder communications system. Hiperface encoders are only manufactured by one company. Most devices that support Hiperface also support SSI, an open vendor protocol supported by most controller manufacturers, and used by Avtron absolute encoders.
Hollow Shaft
Hollow Shaft encoders mount by passing the shaft of the motor into or through the encoder. Hollow shaft encoders are easy to mount and replace but are vulnerable to damage. Also, the weight of the encoder must be considered for small motor shafts < 0.75″ diameter. Avtron offers a full range of hollow shaft encoders, including: AV685, HS25A, HS35A, HS35M, M3, M4, M6, M7, XP45.
I
IEC 61508
IEC 61508 is an international standard published by the International Electrotechnical Commission consisting of methods on how to apply, design, deploy and maintain automatic protection systems called safety-related systems. All Avtron SV850 Encoders are IEC 61508 SIL 2 compliant.
IECEx
IECEx is a directive used worldwide for equipment, including encoders, to be used around or in explosive atmospheres. IECEx certified equipment is NOT necessarily interchangeable with US-based UL Class/Division rated equipment, or ATEX rated equipment. IECEx is an alternative and different system. Avtron offers a full famliy of Explosion Protected, IECEx certified XR encoders, and M6C is also IECEx certified.
Incremental Encoder
An encoder that produces pulses in proportion to distance moved or rotated. Incremental encoders can also have a marker pulse Z, Z NOT (, ) once per revolution to provide a position reference. Avtron produces a full range of incremental rotary encoders.
Industrial EPIC
The preferred encoder connector of most users in North America. It contains a full size terminal strip and, unlike the MS connector, requires no soldering for quick field connections. Avtron offers pin-for-pin exact replacements for competitors’ models using industrial EPIC® style connectors. EPIC® is a registered trademark of the Lapp Group.
Intrinsically Safe/Intrinsic Safety
A system designed to improve equipment safety by limiting spark energy values in equipment used in hazardous areas. Intrinsic Safety is a different system of protection than Explosion Protected or Flameproof. Many Explosion Protected and Flameproof encoders can be replaced with Intrinsically Safe encoders, provided the installation instructions are followed correctly and the system is compliant with the approved installation drawing. Intrinsically safe Avtron XR encoders are available in Level 1 protection and Level 2 protection.
IR LED
Infra-Red Light Emitting Diode is the light source for an optical encoder.
ISO 13849
IEC 61508 is an international standard published by the International Electrotechnical Commission consisting of methods on how to apply, design, deploy and maintain automatic protection systems called safety-related systems.
Isolated Outputs
Isolated outputs provide two or more completely separate output signals from the encoder. These separate signals can be wired to two or more devices, or used for redundant control systems for more uptime. Avtron isolated encoder outputs are always created using fully redundant electronics and sensors, isolated from each other and from the housing for maximum reliability.
J
J1939
J1939 is a fieldbus used by Avtron absolute encoders to report position and speed to a controller. J1939 uses a 4 wire main bus + drop wiring system (CAN). J1939 is hardware-identical to DeviceNet and CANopen, but the encoder messages sent are different; J1939 is primarily used on mobile vehicles. For encoder communications, SSI, Ethernet or Profibus may be faster than J1939. For more information on J1939 – Wikipedia: http://en.wikipedia.org/wiki/J1939
L
Light Mill Duty
Light mill duty encoders are designed for industrial applications but must be protected from contamination, temperature cycling and physical force, including shock, vibration and bearing loads. Examples include AV20, AV25, HS25A and HS35A models.
Light Source
Typically an IR LED or laser which shines through or on the optical disk of an encoder. The light source is received by the optical sensor.
Line Driver
The chip or output circuit that forms the electrical pulses output from the encoder. Avtron has extremely advanced line driver technology to prevent damage from overvoltage and short circuits. Avtron offers optional high-power line drivers to permit Avtron encoder signals to travel farther down long wires to remote controller/drive locations without the need for repeaters or amplifiers.
Lines
Encoders produce pulses that create transitions up and down in a DC voltage. Each transition is called a line. Quadrature encoders with their two channels produce four times as many lines as pulses. Some drive products can be set to count lines in one direction (up/down) or all directions, creating more counts in the drive than the rated PPR (pulses per revolution) of the encoder.
M
M12 Connector
M12 (12mm) connectors are a screw or push-on style connector used by Avtron incremental and absolute encoders. There are different pin quantities, pinouts and keying, depending on the vendor style supported by the product. M12 mating cables are typically overmolded rather than field-solderable, such as MS connectors, or screw terminals, such as EPIC connectors.
M23 Connector
M23 (23mm) connectors are a screw or push-on style connector used by Avtron incremental and absolute encoders. There are different pin quantities, pinouts, and keying, depending on the vendor style supported by the product. M23 mating cables are typically overmolded rather than field-solderable, such as MS connectors, or screw terminals, such as EPIC connectors.
Magnetic Encoder
Magnetic and magnetoresistive encoders typically use a magnetized rotor with north and south poles lined up around the perimeter of the disk. A magnetoresistive sensor detects the transitions, and these are the counts or pulses generated by the encoder. Magnetic encoders withstand dirt, dust, water and temperature changes far better than optical encoders.
Magnetic Rotor
A magnetized disk with multiple north and south poles lined up around the perimeter of the disk. A magnetoresistive sensor detects the transitions and generates the pulses generated by the magnetic encoder.
Magnetoresistive Sensor
A sensor that detects the magnetic poles on an encoder’s magnetic rotor and transforms them into pulses. Avtron magnetoresistive (MR) sensors use advanced technology to reject external magnetic signals such as brake solenoids and motor magnetic fields. MR sensors enable Avtron magnetic encoders to ignore dirt, oil, water and other contaminants.
Marker Pulse
The Marker Pulse occurs once per revolution. The purpose of the marker pulse is to provide a repeatable home position location for positioning applications. The marker pulse is often abbreviated as “ØZ” or “Z” in the USA and “C” or “N” in Europe.
Mill Duty
Mill duty encoders are sturdier than light mill duty and can withstand more shock, vibration and bearing loads. Mill duty encoders must be protected from temperature cycling and contaminants.
MS Mini Connector
This is a 10 pin military style connector used for encoders. It includes a set of locking pins and slots instead of the threaded mating system on most MS connectors. It is also known as “Mini-Twist-Lock”, “Bayonet” and “Baldor connector”.
Mini-Twist-Lock Connector
This is a 10 pin military style connector used for encoders. It includes a set of locking pins and slots instead of the threaded mating system on most MS connectors. It is also known as “Bayonet”, “MS Mini” and “Baldor connector”.
Missed Pulses
Errors made by an encoder when a pulse should have been generated due to movement but was not. They are often caused by contamination on optical disks that cause a line to be missed.
Modbus/TCP
Modbus/TCP is an Ethernet-based communication fieldbus used by Avtron encoders to communicate speed and position to a controller. For more information on Modbus/TCP – Wikipedia: http://en.wikipedia.org/wiki/Modbus
Modular Encoders
Modular encoders mount to a machined C-face or flange adapter on the motor (drive or non-drive end). Modular encoders consist of a rotor that mounts on the shaft, and a stator that bolts to the motor frame. Modular encoders are very rugged, and Avtron encoders feature Wide-Gap sensors to avoid complex shimming or fitting to the motor. Modular C-face encoders are typically used on DC motors; but some AC motors such as Rockwell’s RPM III AC and Marathon’s Blue and Black Max motors have C-faces standard on the non-drive end for mounting an encoder.
Motor Shaft Currents
The high-speed switching of variable frequency drives that is used to control the speed of motors often produces current which flows from the motor shaft to ground, or from end-to-end of the motor. These currents are highly destructive to both motor and encoder bearings. Preventing shaft current damage is essential. Most Avtron hollow shaft encoders include features to prevent motor shaft current damage. For more information: http://www.avtronencoders.com/knowledge-base/eliminating-damage-from-motor-shaft-currents-through-tachometers-and-encoders or visit Wikipedia: http://en.wikipedia.org/wiki/Shaft_voltage
MR
Magnetoresistive (MR) sensors are used in Avtron encoders to provide high accuracy and superior reliability versus optical sensing systems. For more information on magnetoresistivity – Wikipedia: http://en.wikipedia.org/wiki/Magnetoresistive
MS Connector
The most used encoder connector style in North America. Available in 6, 7 and 10 pin versions, with 10 pins being the most common. Avtron offers pin-for-pin exact replacements for competitors’ models using MS connectors. MS connectors are extremely reliable but require soldering. Many users prefer industrial EPIC ® style connectors instead. EPIC® is a registered trademark of the Lapp Group.
Multi-turn
Multi-turn refers to the capability of an absolute rotary encoder to output the position accurately, including how many times the shaft has been rotated. The absolute encoder will report this position correctly, including both the position within 1 revolution as well as the total number of turns, whether the encoder was powered when the turns took place or not. Avtron multi-turn absolute encoders do not use batteries, and Avtron absolute magnetic encoders do not use gears for maximum reliability. Example: Avtron AV30 severe duty absolute encoder. For more information on absolute rotary encoders – Wikipedia: http://en.wikipedia.org/wiki/Rotary_encoder
N
NEMA 56C
A NEMA 56C face or flange mount, also known as bearingless or pancake encoder, is a 4.5″ flange with (4) bolts located in a 5.88″ circle. Originally designed as the standard for mounting solid shaft, coupled tachometers on flange adapters, the NEMA 56C is also a standard for mounting modular encoders. Avtron AV56 THIN-LINE II™ encoders mount on NEMA 56C faces. Marathon Blue Max and Black Max AC motors feature a NEMA 56C face on the non-drive end.
NEMA FC
A NEMA FC face mount is a 8.5″ flange with (4) bolts located in a 7.25″ circle. Originally used for mounting solid shaft, coupled tachometers using flange adapters, the NEMA FC 8.5″ face is a standard for mounting modular encoders (Drawing “A”). Avtron AV85 and AV850 encoders mount directly on NEMA FC 8.5″ faces (Drawing “B”).
O
One-Speed Resolver
One-speed resolver refers to feedback that is absolute and unique over an entire 360° rotation. Higher-speed encoders provide absolute feedback over a fraction of a turn, then repeat their output. Example: a 4-speed resolver is absolute over 90°.
Optical Disk
An optical disk is typically a glass, metal or plastic disk with fine lines or slots etched around the perimeter that interrupt the beam of light from the light source to an optical sensor. Optical disks can be quite fragile. Avtron uses only shatterproof optical disks with Wide-Gap technology.
Optical Encoder
An optical encoder typically uses a light source shining through or reflecting off an optical disk with lines or slots that interrupt the beam of light to an optical sensor. Electronics count the interruptions of the beam and generate the encoder’s output pulses.
Optical Errors
Optical errors include false pulses, missed pulses and quadrature errors that are generated when there is any type of contamination (dirt, oil, water, condensation) on the optical disk.
Optical Sensors
Optical sensors are typically phototransistors or other light sensors which sense the light emitted by the light source, as interrupted by, or passed through, the optical disk.
P
Parallel
Parallel outputs are used by some Avtron absolute encoders to communicate the position to a controller. One wire is used for each bit of resolution, plus one wire for each turn for multi-turn units. Parallel outputs are used for older controllers; newer controllers typically use a communication fieldbus (such as SSI or Profibus) to read the encoder position.
Powerlink
Powerlink is an Ethernet-based absolute encoder communications hardware and software standard used by Avtron absolute encoders. For more information about Powerlink – Wikipedia: http://en.wikipedia.org/wiki/Ethernet_Powerlink
PPR
Pulses Per Revolution. Most Avtron encoders output quadrature pulses, with four times as many lines as pulses. Often lines can be counted in the drive/speed controller for higher resolution applications.
Profibus DP
Profibus DP is a fieldbus used by Avtron absolute encoders to communicate speed and position to a controller. For more information about Profibus DP – Wikipedia: http://en.wikipedia.org/wiki/Profibus
Profinet
Profinet (IO) is a communications fieldbus used by Avtron absolute encoders to communicate speed and position to a controller. Profinet carries Profibus messages over an Ethernet network to and from the encoder. For more information on Profinet – Wikipedia: http://en.wikipedia.org/wiki/Profinet
Pulses
Pulses are also known as counts and are the low voltage output transitions which indicate movement of the encoder. Encoders are rated by resolution or PPR (pulses per revolution). Pulses are not the same as lines.
PY Face
A PY Face is a 2.0″ flange with (4) bolts located in a 3.978″ circle. It is used for mounting solid shaft, coupled 5PY style DC tachogenerators using flange adapters. Avtron AV44 encoders directly fit PY face mounts. An adapter is available to fit AV485 to PY faces as well.
Q
Quadrature
To determine which direction an encoder is revolving, encoders output quadrature signals – two streams of pulses, A & B, generated at 90° timing angles (Also called A Quad B). A leading B indicates rotation in one direction; B leading A indicates the encoder is rotating in the opposite direction. Example: “A leads B with clockwise rotation as viewed from the encoder face on an HS45 encoder.” Many encoders with quadrature outputs also have complementary outputs: A NOT and B NOT signals.
Quadrature Errors
Failures of the encoder to generate properly formatted quadrature signals. Typically, these are failures to create the proper 90° signal separation between the A and B channel outputs, with a less than perfect stream of square waves. Most controllers, when presented with a quadrature error, will report a drive fault or encoder fault and then shut down.
R
RE210
An analog tachogenerator manufactured by Baldor/Reliance, NEMA 56C face or foot mount, coupled. It may be replaced by an Avtron encoder combined with a K661 converter solution.
Reluctance
An early style of analog tachometer. It only provides output above a minimum speed. The output is a low-power analog sine wave. Avtron offers the M460 reluctance tach, which is not compatible with modern encoders.
Resolution
Resolution describes how many individual slices or positions can be reported by an incremental or absolute encoder. For incremental encoders, the number of PPR (pulses per revolution) expresses resolution; for absolute encoders, PPR, or counts per turn or bits of resolution, may be listed.
Resolver
A device typically used to indicate absolute rotary position (angle) and velocity. A resolver is excited by an AC sine wave and produces amplitude modulated (analog) AC waves which indicate the rotor position. Avtron offers the Rotasyn Resolver.
Rotary Encoder
A rotary encoder provides position and/or speed feedback information about a rotating shaft. Rotary encoders may be hollow shaft, no-bearing modular, coupled solid shaft style. They may provide absolute positioning information or incremental velocity feedback. Avtron rotary encoders are designed and built to be far more reliable than ordinary rotary encoders. Avtron encoder white papers on our blog provide more details of how and why Avtron rotary encoders are more reliable.
Rotor
The disk-shaped portion of the modular encoder that is mounted on the motor shaft. Avtron modular encoders use magnetic rotors.
S
Sandwich
An older style of encoder that fits between an existing solid shaft coupled tachometer and the motor. It is commonly replaced by modular encoders such as the Avtron AV56 THIN-LINE II™.
Seal Failure
Many encoders come sealed from the factory, but as they are temperature cycled, the air inside expands and contracts at a different rate from the air outside the encoder. This puts pressure on the seals of the encoder and eventually breaks them down, creating an unobstructed path to the inside of the encoder. Likewise, external pressure (wash-downs, submersion) creates the same path. If an encoder has seal failure, contaminants get into the encoder and cause errors in optical encoders. Avtron heavy mill duty and severe-duty encoders are highly resistant to seal failure, and feature magnetic technology to ignore most contaminants.
SELV Power Supply
SELV power supplies safely limit current and voltage using a separation system from higher voltages. For ATEX Zone 2, IECEx Zone 2 and UL Class I, Div 2 applications, XR encoder installations may be simplified by utilizing a SELV power supply instead of a separately fused DC circuit. For more information on SELV power supplies – Wikipedia: http://en.wikipedia.org/wiki/Extra-low_voltage
Sensor Crash
When the rotating disk in an encoder contacts the sensor (optical or magnetic/magnetoresistive), it damages or destroys the sensor. Sensor crashes can be caused by excessive vibration, shaft runout or alignment problems in encoder mounting. Avtron encoders feature Wide-Gap technology to eliminate sensor crashes.
Severe Duty
Severe duty encoders have the best ability to withstand temperature cycling, extreme temperatures, contaminants, bearing loads and physical abuse.
Shaft Current
The undesirable electrical current flow common to motors controlled by variable speed drives. This current attempts to circulate within the motor or discharge to ground. Avtron encoders are protected against shaft currents.
Shaft Grounding
To eliminate damage from shaft current, the encoder may be provided with a conductive brush that contacts the motor shaft and discharges the voltage before it damages the motor or encoder bearings. Many Avtron encoders offer a shaft grounding kit option.
Shaft Runout
The wobbling motion produced by a shaft that is not perfectly true and straight. Shaft runout is often abbreviated T.I.R. (Total Indicated Runout).
Shimming
Often, to produce precise stub shaft, modular encoder or foot mount installation, shims are placed between the two items to be aligned. Avtron encoders are designed to eliminate the need for shimming. Many competitors’ modular encoders still require shimming for proper operation.
Shims
Thin pieces of metal used to precisely space two parts. They are used for shimming a stub shaft, encoder rotor or foot mount installation.
Sine-Cosine Encoder
An incremental device typically used to indicate rotary position and velocity. A sine-cosine encoder outputs a preset number of cycles per revolution (CPR) of analog sine waves, along with cosine waves (offset by 90°). Most sine-cosine encoders output ~1V peak-to-peak. Nidec Industrial Solutions does not presently offer sine-cosine models because sine-cosine signals are very vulnerable to electrical interference.
Single-turn (ST)
Single-turn refers to absolute encoders – the encoder accurately reports the position within 360 degrees of travel to the resolution specified. Multiple turns are ignored – multi-turn absolute encoders are required to track and report position over multiple turns as well as the position within 1 turn. Avtron absolute single-turn encoders are more durable because they don’t use glass disks. For more information about absolute rotary encoders – Wikipedia: http://en.wikipedia.org/wiki/Rotary_encoder
Solid Shaft
Solid shaft encoders are coupled to the shaft to be measured. The solid shaft encoder body is typically C-face mounted using a flange adapter, or some models can be foot mounted.
SSI
SSI (Synchronous Serial Interface) is a fieldbus used by Avtron absolute encoders to communicate speed and position to a controller. SSI is extremely simple and fast. SSI is also an effective, open vendor alternative to proprietary encoder fieldbuses such as EnDAT and HyperFace. For more information about SSI – Wikipedia: http://en.wikipedia.org/wiki/Synchronous_Serial_Interface
Stator
The portion of a modular encoder that bolts to the motor frame.
Stub Shaft
The portion of the shaft (often on the non-drive end of the motor) used to mount an encoder. To add an encoder to a motor or other shaft that lacks enough extra shaft length to install the encoder, an additional shaft length is added. The stub shaft is threaded into the center of the motor shaft, or the existing motor shaft is enclosed in a sleeve that grips the shaft. Nidec Industrial Solutions offers many standard and custom stub shafts.
T
T.I.R.
Total Indicated Runout. This is a measurement of how much a shaft wobbles with each revolution (shaft runout).
Tachometer
Also known as a tach, a device which indicates speed of rotation. Modern tachometers are actually rotary incremental encoders which indicate position, speed and direction of rotation.
Torque Arm
A type of anti-rotation arm used to mount hollow shaft encoders to large frame motors. It features a threaded rod for adjustable radius.
Twisted Pair Cable
Incremental and absolute encoder signals should be carried over twisted pair cables. Twisted pair cables enable the elimination of external noise signals, as the signals show up as “common mode” noise on both wires in the pair. The controller wired for differential communication will remove the external noise from the encoder signal. When wiring Avtron incremental encoders, be sure to wire the complementary signals (ex: A, A/) in one twisted pair. Do not mix phased signals (ex: A, B) in the same twisted pair. For absolute encoders, follow the bus recommendations for using the twisted pairs in the required cable type.
U
UL Listed
UL Listed Avtron encoders can be directly applied to any hazardous-duty application which requires Class and Division, Class and Zone or AEX certification. Note that UL Listing is a different system than ATEX or IECEx. Ensure the model you select has the UL listing which meets the application requirements.
UL Recognized
UL Recognized Avtron encoders are usable for OEM applications requiring UL Class I, Division 2. The OEM must select the model which meets the application requirements, and ensure that the system as a whole meets the application and safety requirements. Note that UL Recognition is a different system than UL Listing, ATEX or IECEx. Most Avtron XR encoder models are available in both UL Recognized and UL Listed versions. UL Recognized XR encoders offer a broader range of connector options than UL Listed XR encoders.
V
VSO
Vane Switched Oscillator. This is an older type of encoder that produces a unique signal output that cannot be replaced with a modern encoder. Contact Avtron for upgrade path.
W
Wide-Gap Technology
Avtron encoders use special optical sensors and magnetoresistive sensors, combined with proprietary circuit designs to allow the sensor to be located much farther from the magnetic rotor or optical disk. This eliminates sensor crashes and makes mounting easy and forgiving of mechanical variation.
Wiegand wire
Wiegand wires generate a pulse of electricity in a coil as a magnet passes near the wire. Wiegand wires are used in Avtron absolute magnetic encoders to self-power the multi-turn counting engine, so even if the encoder has no power when turned, the absolute encoder correctly reports the number of turns and position. This allows Avtron to eliminate the glass disks and gears that cause failures in other absolute encoders. For information on the Wiegand effect – Wikipedia: http://en.wikipedia.org/wiki/Wiegand_effect and Wiegand wire – Wikipedia: http://www.epanorama.net/sff/Power%20Electronics/Transformers_and_Magnetics/Magnetics%20-%20Wiegand%20Wire.pdf