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Catalogue Linear Encoder Brochure

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Encoder Selection Guide

Measuring Methods


Application / Usage	Measuring Accuracy /m	Resolution	Measuring	Output Signal	Model-Code
				~IIVpp	SHG-VP
				~IVpp with Single Point Reference	SHG-VS
For long measuring	±I0\|jm	0.5-IÜMm	Single Scale 11m	IlMApp	SHG-VM
lengths	±I0\|jm	0.5-IÜMm	Modular to 30m	~IVpp	SHG-VV
				TTL	SHG-TT
				TTL with Single Point Reference	SHG-TS
For high accuracy with	±5_Mm	0.1-IÜMm	Up to 1m	TTL	MHG-TT
limited space	±5_Mm	0.1-IÜMm	Up to 1m	~IVpp	MHG-VP/VV/VM
For long lengths with low accuracy requirements	±25_Mm		Up to 32m	TTL	MAG-TS &TT
				TTL with Distance Coded	SHG-TC
				RS485	SHG-A4
For absolute position	±3,5, I0\|jm	0.5-IÜMm	Up to 6.5m	SSI Gray or Binary	SHG-AG or AB
measurement	±3,5, I0\|jm	0.5-IÜMm	Up to 6.5m	RS232	SHG-A2
				Fanuc	SHG-AF
				Gray & Parity	SHG-AS

Stainless steel tube

Nicke chrome elements

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Sectional view

Spherosyn Technology Incremental

Spherosyn technology is an inductive encoder that is made up of

two main assemblies, the reader head and the scale. The scale is a

length of stainless steel tube housing a column of precision elements. The elements are maintained under compression, the compression load being set during manufacturing to calibrate the scale The head, which fits around the scale moves in a linear

motion along the scale length, comprising a rectangular aluminium

casting containing a coil assembly and electronics.

Figure 1 shows the arrangement of coils in the head. There are six sets of pick-up coils . Each set consists of four identical windings that are spaced at intervals of one pitch. As a result of this spacing each coil in a set is positioned over an identical part of an adjacent element. All the coils of a set are connected together in series. Over the pick-up coils is the drive coil. The element within the scale cause the permeability of the scale to vary periodically over a pitch. The voltages induced in each of the sets of pick-up coils vary according to the relative positions of the coils to the underlying Figure 1 PlchvCmti

elements.The variation of the amplitude of the induced signals with displacement along the scale is shown in Figure 2a. The coils are spaced such that when one set of coils is at a maximum, e.g. set A, another set spaced one half an element pitch away, set C, will be at a minimum. These coil pairs are combined differentially to produce signals that vary with displacement as shown in Figure 2b.

These combined signals are phase shifted by the electronic circuits in the head. The A-C signal is advanced 45° and the D-B signal is retarded 45°. These signals are added together and filtered. The result is an output signal whose phase varies as the head is displaced along the scale.

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All Newall digital encoders can be connected to a wide range of PLC, CNC, NC and PC applications.

The choice of the encoder depends on five principal factors;

• The first is the level of precision required for the application i.e., in general, a saw conveyor requires a lower precision than a grinding machine.

• The second is the spatial limitations. For instance with an MHG Encoder you are able to fit into a much smaller area than an SHG Encoder

• The third factor is the overall measuring length of the

application.

• The fourth is the required resolution.

• The fifth is the output signal.

Signal amplitude

Figure 2b

M'cos (2:Pi/p) j. 0 p/4 p/2

NEWALL MEASUREMENT SYSTEMS BEI TECHNOLOGIES, INC. ⁵