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A Quad B
refers to the set of output quadrature signals from an incremental 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.
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Absolute Encoder
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.
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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.
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Analog Tachogenerators
also known as DC 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. Nidec-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.
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Anti-Rotation Arm
is 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.
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Axial Shaft Movement
is 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 encoders.
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C-Face
is 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.
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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.
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Complements
are 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.
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Coupling/Coupled
refers to a flexible device that is used to link a solid shaft encoder to the shaft to be monitored. Nidec-Avtron strongly recommends isolated, flexible disk style couplings wherever possible to maximize encoder bearing life. For large axial shaft movements, spider couplings may be used as an alternative.
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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.
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Magnetic Rotor
is 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.
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Magnetoresistive Sensor
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.
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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" in the USA and "C" or "N" in Europe.
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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.
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Missed Pulses
are 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.
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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.
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MR
(Magnetoresistive) Magnetoresistive sensors are used in Avtron encoders to provide high accuracy and superior reliability.
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MS Connector
is the most used encoder connector style in North America. Available in 6, 7, and 10 pin versions, with 10 pins being the most common. Nidec-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.
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Sandwich
is 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™.
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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.
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Severe Duty
encoders have the best ability to withstand temperature cycling, extreme temperatures, contaminants, bearing loads and physical abuse.
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Shaft Current
is 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.
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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.
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Shaft Runout
is 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).
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Stator
is the portion of a modular encoder that bolts to the motor frame.
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Stub Shaft
is 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-Avtron offers many standard and custom stub shafts.