Avtron AV850 SMARTach II Encoders

Avtron AV850 SMARTach II Encoders


  • Heavy Mill Duty
  • Installation in Minutes!
  • Up to 5000 PPR
  • Removable Sensors
  • Wide-Gap Technology, No Air Gap Adjustment Required
  • Mounts Securely to Motor
  • Outputs Fully Short Circuit Protected
  • Self-Diagnostic LED & Alarm Output
  • Sealed Electronics
  • -40°C to +100°C Operation
  • 3 Year No-Hassle Warranty
  • Excellent for Gear Motors and Brake Applications
Outline Drawing

SMARTach II™ Magnetic, Modular Encoder, 8.5" C-Face Mount

AV850 SMARTach II heavy mill duty modular magnetic encoders fit standard 8.5" FC-Face motors. Other models, from 115mm to 12.5", are available to fit other motor sizes, and hazardous duty models: XR850 are also available.

Quite simply, the AV850 is designed to eliminate encoder failures.

All AV850 electronics are fully encapsulated. There are no moving wearing parts. AV850 sensors locate over 4X farther from the rotor than the competition; no more sensor/rotor grinding!

The AV850’s high-power outputs have over 50X more capacity.

Miswiring an encoder is common– and it shouldn’t cost you time or money. The AV850 has full output short circuit and reverse voltage protection, plus surge protection.

AV850 SMARTach II sensors digitally self-tune the outputs to eliminate drive trips caused by poor encoder signals.

AV850 sensors feature unsurpassed diagnostics. If the encoder signal is not ideal, the alarm output and LED inform the machine operator that the encoder should be checked, before a failure occurs! The AV850 even checks the rotor position before you start running!

If you think you need to replace your drives to end your encoder failures, try a better encoder instead. Specify AV850!

Operating Power (Each Sensor): 5-24V, 100mA
Output Format: A Quad B with marker (A,A–, B,B–, Z,Z– )
Frequency Range: 0 to 165 KHz
Maximum Instantaneous Current Output: 3000mA*
PPR: 8 - 5000   Speed: 6000 RPM Max***
Rotor Positioning: Up to +/-0.100" movement/misalignment
Sensor-Rotor Gap: 0.045", +0.015/-0.040" [1.14mm+0.38/-1.0]
Temperature: -40° to 100°C (rotor -40° to 150°C peak)
Electronics: Fully Encapsulated, IP67**
Vibration: 18 g’s   Shock: 1 meter drop test
Weight: 9lbs. [4kg]; 11lbs. [5kg] dual

All dimensions are in inches [millimeters].
Specifications and features are subject to change without notice
*Output option 8; see manual for details.
**Connector options may reduce IP rating.
***Max RPM may be limited
For PPR > 2500 contact factory
  • SMARTach II sensors find problems before they cause failure
  • Replaces Northstar/LakeShore RIM8500™, NexGen 8500; Avtron M193B, M285; GE AN-DG models
  • Resists motor and brake interference noise
  • Reverse voltage protection
  • Mix and match any PPRs with any rotor
  • Permits axial movement up to +/-0.100" [+/-2.54mm]
  • Universal rotor for all GE CD style and many Reliance motors.
  • Optional overspeed switch
  • Optional shaft grounding
Industry General Food & Beverage Pulp & Paper Wood Products Wind Power Crane & Hoist Metals Mining Marine Oil & Gas

Light Mill Duty

AV20, AV25, AV32, AV6A, AV6M, HS25A, HS35A, HS6A, HS6M, K661,

Mill Duty

AV32, HS35M, K661, M185, M3, M3(small), RAHS35M

Heavy Mill Duty

AV115, AV125, AV45, AV5, AV56, AV56S, AV67, AV85, AV850, AV850Test, AVSK, Carlen Replacement, HS45, K661, M4, M4(small), XR115, XR12, XR125, XR45, XR4F, XR5, XR56, XR85, XR850, XR97, XRB1, XRB2

Severe Mill Duty

AV12, AV30, AV485, AV5, AV685, Carlen Replacement, HS40, K661, M484, M6, M6C, M7, XR12, XR485, XR5, XR685, XR97, XRB1, XRB2,
Avtron's AV850 encoders replace many competitive models, including:

Lakeshore/Northstar: RIM TACH 8500, RIM 8500, RIM 8.5, R85Q, R8, RT8, NexGen encoders

General Electric:  GE AN-DG encoders
36C696957AB-1, 36C696957AB-2, 36C696957AA001, 36C696957AA002, 36C696957AA003, 36C696957AA004
36A160614AK-001, 36A160614AK-002, 36A160614AK-003, 36A160614AK-004 , 36A160614BA-002  

Combine AV850 with a K661 to make a great replacement for analog tachogenerators flange mounted to GE CD frame DC motors including:
General Electric GE BC42, BC44, BC62 

AV850 also directly replaces older encoder models from Avtron, including:  SLAPTach M190, M192, M193B, SMARTach M285 encoders (with M284 sensors)
For direct model replacements, try our cross reference page
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In This Section

  • 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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • Face or Flange Mount

    A machined surface (NEMA 56C, NEMA FC) on the non-drive end of the motor is used to mount bearingless or pancake encoders such as Avtron AV56 THIN-LINE II™ encoders. Solid shaft, coupled tachometers also flange mounted using flange adapters, also called flowerpots.

  • 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, AV115 unit on the motor flange. (Drawing "B")

  • Heavy Mill Duty

    Heavy Mill Duty encoders are designed to withstand temperature cycling, extreme temperatures, contaminants, bearing loads, and physical force.

  • 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.

  • 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.

  • 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.

  • 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.


    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")

  • 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.

  • Rotor

    The disk-shaped portion of the modular encoder that is mounted on the motor shaft. Avtron modular encoders use magnetic rotors.

  • 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. Avtron offers many standard and custom stub shafts.

  • 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.

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