Avtron AV685 SMARTach II Encoders

Avtron AV685 SMARTach II Encoders

The Toughest Hollow Shaft Encoder Built!

  • Severe Mill Duty
  • Up to 5000 PPR
  • Replaces Competitive Models Without Rewiring
  • Self-Diagnostic LED & Alarm
  • Outputs Fully Short Circuit Protected
  • Removable Sensors
  • End of Shaft and Thru Shaft Models Available
  • IP66 Enclosure
  • High-Power Output Standard
  • Optional Dual Isolated Outputs
  • 1 Year No-Hassle Warranty
Outline Drawing

SMARTach II™ Magnetic Encoder, 1 1/8" Hollow Shaft Mount

AV685 hollow shaft encoders survive the worst conditions: dust, dirt, liquid sprays, and temperature extremes from -40°C* to +120°C*!

The dual, replaceable sensors are interchangeable between AV485, AV685, and AV850 and feature high-power outputs that drive long cable lengths easily. These AV5 SMARTach II sensors have the best protection of any encoder—from surges, wiring outputs to power, ground, between phases, or even short circuits!

The green diagnostic LED on the sensors assure you that the encoder is outputting ideal signals—no more false drive trips.

If for any reason, the signal is not ideal, the light turns red, and an alarm contact notifies the operator. However, the AV685 keeps working. This enables maintenance to be scheduled, and unscheduled downtime is eliminated!

The durable hollow shaft design tolerates huge axial movements, and withstands more shaft runout than any other encoder available.

So if you want the highest reliability most durable encoder in your mill, select AV685.

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 Cable Length: 2000' [600m] ***
PPR: 8 - 5000
Speed: 4000 RPM Max
Temperature: -40°* to 120°C*
Environmental: IP66**; Nema 4, 13 Rating
Weight: 15 lbs. [6.4 kg]; 17lbs [7.7kg] dual output


All dimensions are in inches [millimeters].
Specifications and features are subject to change without notice.

*-20°C to 80°C Standard.
**Connector options may reduce IP rating.
***Hi-power outputs; may be limited by RPM & PPR; see manual for details.

  • SMARTach II sensors find problems before they cause failures
  • Replaces Avtron M585, M685; Dynapar HS56, HS85 models
  • Optional K661 signal converter for direct replacement of analog tachs (BC42, 46, etc.)
  • Mix and match any PPR’s
  • No sensor shimming required
  • Dual oversize bearings, spaced farther apart
  • Synthetic bearing lubricant for longer life
  • Optional overspeed switch
  • Optional shaft grounding
  • Huge range of stub shaft adapters available to fit shafts from 1 3/8" to 12" & most motor brands
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 AV685 encoders replace many competitive models, including:

Lakeshore/Northstar: HS85, H8, HS56, H5, HD

AV685 is also a great replacement for analog tachogenerators coupled to large brake motors including:
General Electric GE BC42, BC44, BC62

It also directly replaces older encoder models from Avtron, including:  M585, M685, M3-5, M4-5

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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • Severe Duty

    Severe Duty encoders have the best ability to withstand temperature cycling, extreme temperatures, contaminants, bearing loads and physical abuse.

  • 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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