Eltra High Resolution Rotary Encoder. Overview of Incremental and Absolute shaft encoders.

CONTENTS:

1. Definition of high-resolution encoder
2. Main features of incremental series
3. Absolute series
4. Magnetic series
5. Applications

What is a high resolution encoder?

A high resolution encoder is an angle sensor with accuracy of 10,000 ppr. The resolution of a rotary encoder is the number of pulses (or counts) that its wheel makes in one full revolution. Some rotary encoder models can be with ultra-high resolution up to 100,000 ppr.

Optical sensors are traditionally more accurate than magnetic ones. On the other hand, they have less resistance to dirt and mechanical shocks that make impossible to use them in some areas.

High-res encoders work in applications where extremely measurement accuracy is required. It is used for DC motor feedback, CNC machining, telescope tuning, and even for space programs. For a more detailed list, look at the applications section below.

Accuracy of linear devices is determined by a distance between marks on its scale. The smaller this step on the scale, the greater its accuracy. With a high resolution linear encoder, this step can even be 1 nm (10^-6 mm).

High resolution incremental rotary encoder

The resolution of incremental rotary encoders is most often specified in pulses per revolution. Common devices, so-called quadrature, have output digital signals (pulses) in a form of square waves (channels A/B/Z). Some brands are also used different values: counts per revolution (CPR) and lines per revolution (LPR).

ELTRA s.p.a. manufactures the following series of incremental high-resolution optical rotary encoders:

• ER 53
• ER 63
• ER 58 
• ER 38 F/G

ER 53 A/B (up to 10000 ppr) is a blind hollow shaft series. Such units are directly mounting on a motor surface. They have integrated elastic coupling that reduce radial and axial shaft play. Rotation speed reaches 6000 rpm. Models with special metal cover are available for heavy-duty applications.

ER 63 A / D (up to 24000 ppr) is a series of standard encoders with a diameter of 63 mm for applications where high mechanical resistance is required. Due to good reliability, they may work with high radial and axial shaft load. The models have three solid shaft variants: 8, 9.52 and 10 mm. Such equipment is mechanically mounted using synchronous or centering types of flanges.

ER 58 (up to 24000 ppr) is also a series for harsh environments with good mechanical protection. Such models have a solid shaft (6-12 mm) from 1.4305 / AISI 303 stainless steel. The devices coupling by synchronous or clamping flanges. Its housing is made from PA66 glass fiber reinforced or painted aluminum.

ER 38 F/G (14400 ppr) is a miniaturized encoder for general industrial purpose with blind hollow shaft. This series is quite popular to use with small AC motors. The mechanical connection of the device is carried out in two possible ways: with stator coupling or with torque pin.

High resolution absolute encoder

Absolute encoders measure particular absolute position. There are special unique sectors on its wheel, for determine angle displacement. Unlike incremental ones, the absolute encoders measure not number of pulses but a particular position. Therefore, they need to send and receive a data from controllers. It is easier to do, using bits as a value. Absolute encoders may have two variants of resolution:

• Single-turn resolution (ST)
• Multi-turn resolution (MT)

Single turn resolution is a number of bits, or lines, that wheel makes by one revolution.

Multiturn resolution is a number of bits that describes how many such revolutions an encoder can remember.

To convert bits to total ppr value you just need to raise 2 to the power of the number of bits. For example, you have 12 bits Single turn and 13 bits Multiturn resolution that equal 2¹² and 2¹³ ppr (4096 and 8192 respectively).

Eltra Company produces several series of absolute high-resolution optical position encoder:

EAR 58-63 (25 bits) are singleturn encoders with solid or blind shaft variations. The manufacturer produces models with both SSI and Parallel electrical interfaces. Such unit uses OptoASIC sensing technology for its measurements.

AAM 38 (23 bits ST/16 bit MT) is a series of multiturn devices with blind hollow shaft and BiSS-C interface. Due to its metal cover it may work at the harsh condition with temperature up to 105 °C (378,15 K). Such model uses optical operation principle for measurements.

EAMR 58-63 (25 bits ST/40 bits MT) is a multiturn encoder with optical reflective operation principle. It has a rotation speed of 10000 rpm and great (IP 67) protection level.

High resolution magnetic encoder

Magnetic encoders are commonly more reliable units but less accurate. However, Eltra sensing technology made an AAM 33 M series with high precision:

AAM 33 M (8 bits ST / 32 bits MT) has compact miniature structure and belongs to assembly kit type. In addition to its great accuracy, the device has several features. Its bearing-less modular construction makes it quite flexible.

This equipment is the best decision when high accuracy results required in harsh conditions, where you can`t use an optical analogues.

Applications

Eltra encoders with high resolution have proven to be reliable and accurate devices at an inexpensive price. Sensors of the presented type are success fully used in:

• Conveyors
• CNC
• Standard motors
• Stepper motors
• Gear reduction motors
• Robotics
• Industrial cameras
• Military equipment

Eltra encoders are successfully operated in many well-known manufacturing companies in the world. Among our new clients is The Coca-Cola Company. In June 2020, we delivered the first batch of Eltra encoders to Coca-Cola factories in Israel. This proves once again the great confidence of the customers in the products of Eltra s.p.a.

Eltra Trade is the official distributor of Eltra encoders. On our stock, you can find a wide range of cheap rotary and linear encoders.