ABSOLUTE ROTARY ENCODER

ConstructionAbsolute digital type produces a unique digital code for each distinct angle of the shaft. They come in two basic types: optical and mechanical.[edit] Mechanical absolute encodersA metal disc containing a set of concentric rings of openings is fixed to an insulating disc, which is rigidly fixed to the shaft. A row of sliding contacts is fixed to a stationary object so that each contact wipes against the metal disc at a different distance from the shaft. As the disc rotates with the shaft, some of the contacts touch metal, while others fall in the gaps where the metal has been cut out. The metal sheet is connected to a source of electric current, and each contact is connected to a separate electrical sensor. The metal pattern is designed so that each possible position of the axle creates a unique binary code in which some of the contacts are connected to the current source (i.e. switched on) and others are not (i.e. switched off).[edit] Optical absolute encodersThe optical encoder's disc is made of glass or plastic with transparent and opaque areas. A light source and photo detector array reads the optical pattern that results from the disc's position at any one time.This code can be read by a controlling device, such as a microprocessor, to determine the angle of the shaft.The absolute analog type produces a unique dual analog code that can be translated into an absolute angle of the shaft (by using a special algorithm).

ROTARY ENCODER

A rotary encoder, also called a shaft encoder, is an electro-mechanicaldevice that converts the angular position of a shaft oraxle to an analog or digital code, making it an angle transducer. Rotary encodersare used in many applications that require precise shaft unlimitedrotation—including industrial controls, robotics, special purpose photographic lenses[1], computerinput devices (such as optomechanical mice and trackballs),and rotating radarplatforms. There are two main types: absolute and incremental (relative).

Incremental rotary encoder

An incremental rotary encoder, also known as a quadrature encoder or a relative rotary encoder, has two outputs called quadrature outputs. They can be either mechanical or optical. In the optical type there are two gray coded tracks, while the mechanical type has two contacts that are actuated by cams on the rotating shaft. The mechanical type requires debouncing and is typically used as digital potentiometers on equipment including consumer devices. Most modern home and car stereos use mechanical rotary encoders for volume. Due to the fact the mechanical switches require debouncing, the mechanical type are limited in the rotational speeds they can handle. The incremental rotary encoder is the most widely used of all rotary encoders due to its low cost: only two sensors are required.
The fact that incremental encoders use only two sensors does not compromise their accuracy. One can find in the market incremental encoders with up to 10,000 counts per revolution, or more.
There can be an optional third output: reference, which happens once every turn. This is used when there is the need of an absolute reference, such as positioning systems.
The optical type is used when higher RPMs are encountered or a higher degree of precision is required.
Incremental encoders are used to track motion and can be used to determine position and velocity. This can be either linear or rotary motion. Because the direction can be determined, very accurate measurements can be made.
They employ two outputs called A & B which are called quadrature outputs as they are 90 degrees out of phase.
The state diagram:

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GERBER SPREADER

Spreading Table Model G
The GERBER spreading table model G is designed to handle spreaders with a roll weight capacity from 50 kg up to 250kg. It is available with and without air flotation and one table top surface for both manual and automatic cutting.

Cloth Unwinding Truck
Eliminates double handling. Pull cloth directly from the truck onto the cutting table. Accommodates 54-96 in (137-244 cm) goods. 2,000 lb (907 kg) capacity.

Material Roll Loader
This system automatically loads and unloads material rolls onto and off of the spreading system. It accommodates rolls weighing up to 100 kg (220 lb).

Single-Ply Feeder
The single-ply material feeding device is used in conjunction with conveyorized cutters. It ensures tension-free spreads and aligns material edges accurately using an infrared edge control device.