Siemens SLI-5310 Instruções de Operação descarregar pdf (Página 27)

27

Scanning methods

Photoelectric scanning

Most HEIDENHAIN encoders operate

using the principle of photoelectric

scanning. Photoelectric scanning of a

measuring standard is contact-free, and as

such, free of wear. This method detects

even very ﬁ ne lines, no more than a few

microns wide, and generates output

signals with very small signal periods.

The ERN, ECN, EQN, ERO and ROD, RCN,

RQN rotary encoders use the imaging

scanning principle.

Put simply, the imaging scanning principle

functions by means of projected-light

signal generation: two graduations with

equal or similar grating periods are moved

relative to each other—the scale and the

scanning reticle. The carrier material of the

scanning reticle is transparent, whereas

the graduation on the measuring standard

may be applied to a transparent or

reﬂ ective surface.

When parallel light passes through a grat-

ing, light and dark surfaces are projected at

a certain distance. An index grating with

the same or similar grating period is locat-

ed here. When the two gratings move in

relation to each other, the incident light is

modulated: if the gaps are aligned, light

passes through. If the lines of one grating

coincide with the gaps of the other, no light

passes through. A structured photosensor

or photovoltaic cells convert these varia-

tions in light intensity into nearly sinusoidal

electrical signals. Practical mounting toler-

ances for encoders with the imaging scan-

ning principle are achieved with grating pe-

riods of 10 μm and larger.

Other scanning principles

Some encoders function according to other

scanning methods. ERM encoders use a

permanently magnetized MAGNODUR

graduation that is scanned with magneto-

resistive sensors.

ECI/EQI/EBI and RIC/RIQ rotary encoders

operate according to the inductive measur-

ing principle. Here, moving graduation

structures modulate a high-frequency sig-

nal in its amplitude and phase. The position

value is always formed by sampling the

signals of all receiver coils distributed even-

ly around the circumference. This permits

large mounting tolerances with high resolu-

tion.

Photoelectric scanning according to the imaging scanning principle

LED light

source

Condenser lens

The ECN and EQN absolute rotary encod-

ers with optimized scanning have a single

large photosensor instead of a group of in-

dividual photoelements. Its structures have

the same width as that of the measuring

standard. This makes it possible to do with-

out the scanning reticle with matching

structure.

Graduated

disk

Incremental track

Absolute track

Structured photosensor

with scanning reticle

Antriebsgeber_en_2013.indd 27 12.11.2013 06:54:25

1 2 ... 22 23 24 25 26 27 28 29 30 31 32 ... 95 96

Comentários a estes Manuais

Sem comentários