H. Kuhnke Ltd, Romsey, UK
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Encoder Overview
Hengstler Rotary Encoders for Industry

Rotary encoders are products which measure the angular position and speed of a turning shaft. An Incremental encoder divides a single turn into a specific number of equally spaced pulses, typically between 1 and 10,000 pulses per revolution (ppr) and it can also be used to measure the number of turns. Removal of power causes all position data to be lost. An Absolute encoder will measure the same angular position, direction and number of turns (if required) as an incremental encoder, but retains this positional data when power is removed.

Incremental encoders are relatively simple and low cost, requiring just basic mechanical skills to fit, and wire to a suitable controller. All Hengstler incremental encoders provide 'quadrature' A&B outputs as standard. These consist of two channels 90 electrical degrees out of phase. The channels can be used to measure distance and speed. Additionally the two channels can be fed into suitable circuitry to determine direction of movement, based on the phase relationship between the channels. A third one pulse per revolution N channel is also provided as standard and can be used to count and monitor the number of completed turns or provide a start position. The incremental encoder will communicate with a specific controller that reads A, B & N and which may display count, or have output functions to perform whatever the applications require. See "Encoder Controller".

Absolute encoders are more complex because of their ability to define an absolute position. The number of turns and angular resolution is coded into data bits typically up to 14 Bit for single turn and 12 Bit for multi-turn. This ability to encode a single turn means that an absolute encoder can be used to give greater resolution than an incremental encoder, but still be used for angular position only. Similarly single turn encoders can be used to determine speed.

Absolute encoders provide data in digital form with parallel or serial outputs. One of the common serial outputs is SSI (Synchronous-Serial Interface) which is a digital point to point interface. Over the years fieldbus protocols have been developed to enable fast data exchange over networks and it has become common to fit absolute encoders with fieldbus interfaces.

Hengstler absolute encoders are available with a variety of fieldbus interfaces, typically BISS, PROFIBUS, DeviceNet, SucoNet, Interbus and CANopen. We show them on this site separately because we believe you are already committed to a particular protocol.

Special Applications
Stainless Bodies, Explosion Proof, ATEX, Fully Immersible, Food Industry

Most Rotary Encoders are designed for standard industrial applications, typically with IP64, or at best IP67 protection. But many specialist industries call for corrosion proof bodies, ATEX compliance, or protection to IP69. Special rotary encoders, both incremental and absolute are available from The Encoder Company. We have grouped these together as one unique range.

Standard Incremental Encoders
Solid & Hollow Shaft
1 - 10,000 ppr
5VDC & 10-30VDC
RS422 & Push/Pull connections
Up to IP67

Small Incremental Encoders
Solid Shaft & Panel Mount
Lower resolutions
5VDC & 10-30VDC
Up to IP64

Standard Absolute Encoders with SSi / BiSS
Solid & Hollow Shaft
Single & Multiturn
Up to IP67

Standard Absolute Encoders with PROFIBUS
Solid & Hollow Shaft
Single & Multiturn
Up to IP67

Standard Absolute Encoders with INTERBUS
Solid & Hollow Shaft
Single & Multiturn
Up to IP67

Standard Absolute Encoders with CANLayer 2 & CANopen
Solid & Hollow Shaft
Single & Multiturn
Up to IP67

Standard Absolute Encoders with DeviceNet
Solid & Hollow Shaft
Single & Multiturn
Up to IP67

Standard Absolute Encoders with SucoNet
Solid & Hollow Shaft
Single & Multiturn
Up to IP67

Special Purpose Encoders
ATEX, Explosion Proof
IP69, Food Industry etc
Incremental & Absolute

Resolvers
Motor Feedback Encoders
Up to IP67