NC Linear Scale Systems

Detection principle of electromagnetic induction system (ABS ST700)

Basic operation principle of electromagnetic induction system

Coil A

L

I

V

∼

Coil B

[Figure 1] Electromagnetic induction system encoder principle

When a current (I1) that changes over time is passed through coil A, a magnetic flux is created in the vicinity of coil A.

This causes an inductive current (I2) to flow in coil B, in a direction that cancels out the magnetic field.

Magnetic permeability between coils is largely identical in air, water, or oil.

Electromagnetic induction type sensor has excellent water resistance and oil resistance.

P

Voltage (V)

Exciter coil

L

2 2

I

Displacement

Scale coil

Displacement magnitude

Multi-track design allows configuration of absolute encoder

Coils arranged at constant pitch on scale

P

[Figure 2] Electromagnetic induction scale detection principle

Electromagnetic induction is a phenomenon that occurs, for example, when two coils are arranged facing each other, as shown in Figure 1, and a time-varying current (I1) is passed through coil A. This will cause an induced current (I2) to flow in coil B, in a direction that cancels out the magnetic field.

The electromagnetic induction type linear scale uses this phenomenon to convert a displacement magnitude into an electrical signal. The operational principle of the sensor section is shown in Figure 2. A number of scale coils are arranged with precise spacing on the main scale. The moveable sensor section that detects displacement carries an exciter coil and a corresponding detector coil. A current is sent through the exciter coil, thereby creating a magnetic flux that induces a current in the facing scale coil. The magnetic flux created in turn by that current induces a current in the facing detector coil. The degree of inductive coupling between the coils changes according to the displacement magnitude of the sensor section, allowing a sinusoidal signal with a cycle that corresponds to the pitch of the scale coils to be obtained.

By using an electrical circuit that performs interpolation

(division) of this sinusoidal signal, displacement can be measured with fine resolution.

NC Linear Scale Systems System Diagram Applications

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Applications

NC Linear Scale Systems System Diagram Applications

Semiconductor fabrication equipment

Dicing saw positioning

AT Series - Reference

Lithography equipment

Scanning stage positioning

Linear scales

ST Series - Reference

Linear scales

Electron microscope

Mask observation, circuit pattern measurement, defect inspection, etc.

Silicon wafer

XY table

(with integrated linear scales)

Electron beam

CCD camera

Work chamber

Monitor

ST Series - Reference

Vacuum pump

XY テーブル駆動方式

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