Linear Position Measurement: Draw-Wire & Magnetic Sensors
SIKO draw-wire encoders measure strokes up to 6 m, in-cylinder versions sit inside hydraulic cylinders, and magnetic tape sensors measure long axes down to micrometre resolution.
Linear travel is awkward to measure: linear scales get expensive over long strokes, limit switches only give end positions, and hydraulic cylinders need feedback without exposed rods that get damaged.
Types of linear position measurement
Draw-wire encoders
A wire pulled from a spring-loaded drum turns a sensor. Fast to mount, long strokes, potentiometer, voltage, current or encoder output.
Models: SG5 (600 mm) · SG10 · SG20 · SG30 · SGP/1 (6000 mm) · SG21 / SG31 for rotary encoder mounting
In-cylinder draw-wire
Installed inside the hydraulic cylinder, pressure-resistant up to 350 bar, with absolute output.
Models: SGH10 (1000 mm) · SGH25 (2500 mm) · SGH50 (5000 mm)
Magnetic incremental sensors
A non-contact sensor reads a magnetic tape or ring. Resolution down to 0.2 µm, insensitive to dirt and wear-free.
Models: MSK1000 · MSK5000 · MSK500/1 · MSK320 · MSK2000 · LE100
Magnetic absolute sensors
Absolute position on magnetic tape, with no reference run, and SSI or RS485 output.
Models: MSA510 · MSA511
What to specify
| Parameter | What to check |
|---|---|
| Measuring length | Draw-wire from 600 mm (SG5) to 6000 mm (SGP/1); magnetic tape for long axes. |
| Absolute or incremental | Need the position at power-up without homing? Choose absolute (SGH, MSA), or a draw-wire with an absolute rotary encoder. |
| Resolution & accuracy | Draw-wire suits mm-level positioning; magnetic sensors go to µm level (MSK1000: 0.2 µm). |
| Output | Potentiometer, voltage or current; incremental; SSI / RS485; CANopen (SGH). Match your PLC input. |
| Mounting & environment | Draw-wire needs only two fixing points. For hydraulics, put the sensor inside the cylinder (SGH). Magnetic sensors are non-contact and dirt-tolerant. |
21 models in our range
Draw-wire sensors 10
Draw-wire encoder SG5
Miniature design · Universal applications…
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Siko SG10
Compact design · Universally applicable thanks to standardized interfaces…
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Siko SG20
Compact design · Universally applicable thanks to standardized interfaces…
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Siko SG21
Small design for rotary encoder mounting · Measurement lengths up to 2000 mm…
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Siko SG30
Compact · Robust design…
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Siko SG31
Robust design · Measuring lengths up to 3000 mm…
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Siko SGH10
Measuring range 0 … 1000 mm (39.37 inches) · Absolute measuring system…
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Siko SGH25
Measuring range 0 … 2500 mm (98.42 inches) · Absolute measuring system…
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Siko SGH50
Measuring range 0 … 5000 mm (196.85 inches) · Absolute measuring system…
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Siko SGP/1
Robust design · Measurement lengths up to max. 6000 mm…
View Details →Magnetic sensors, incremental 9
Siko LE100
Repeat accuracy max. ±1 μm · Status LED display Works with MB100/1 magnetic tape…
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Siko MS500H
Compact design of sensor and connector · To be connected to AP10S or AP20S…
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Siko MSA
To be connected to magnetic displays MA505 and MA561 · Max. resolution depends on downstream electronics unit…
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Siko MSK1000
Max. resolution 0.2 μm · Repeat accuracy ±1 μm…
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Siko MSK2000
Linear resolution 0.25 mm · Repeat accuracy of ±1 increment…
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Siko MSK320
Max. resolution 12.5 μm max. resolution 0.006° with MR320 or MBR320 (250 poles) · Repeat accuracy ±0.04 mm Repeat accuracy of ±1 increment…
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Siko MSK320R
Enhanced safety owing to independent output channels 2 magnetic sensors and 2 signal conditioners in one sensor head · Works with MB320/1 magnetic tape, MRI01 or MR320 magnetic ring, MBR320 magnetic tape ring…
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Siko MSK500/1
Max. resolution 5 μm · Speed-proportional signal output…
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Siko MSK5000
Max. resolution 1 μm · Repeat accuracy ±0.01 mm Repeat accuracy of ±1 increment…
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Where they're used
Hydraulic cylinder position
In-cylinder SGH sensors for presses, mobile machines and lifting.
Lifts & platforms
Height of scissor lifts, platforms and masts.
Saw & cutting carriages
Long-stroke carriage position on woodworking and metal saws.
Machine axes
Magnetic tape measurement on linear axes and slides.
Gantries & handling
Position of storage, handling and transfer systems.
Common questions
What is a draw-wire sensor?
Also called a string potentiometer or wire-actuated encoder: a measuring wire is wound on a spring-loaded drum. As the moving part pulls the wire out, the drum turns a potentiometer or encoder, converting linear travel into an electrical signal.
Draw-wire or magnetic tape: which should I use?
Draw-wire is quick to install and economical for strokes up to several metres at millimetre-level accuracy. Magnetic tape systems are non-contact and reach micrometre resolution, and are better for precise machine axes.
Can a position sensor be installed inside a hydraulic cylinder?
Yes. SIKO's SGH draw-wire sensors are built into the cylinder, are pressure-resistant up to 350 bar and provide an absolute signal, for strokes up to 1000, 2500 or 5000 mm.
What is the longest stroke a draw-wire sensor can measure?
In the current range, the SGP/1 measures up to 6000 mm.
What outputs are available?
Depending on the model: potentiometer, voltage or current analog output, incremental signals, SSI or RS485 (magnetic absolute), and CANopen (SGH). Some draw-wire mechanics (SG21, SG31) accept a standard rotary encoder so you can choose the interface.
- Established
- 1994
- Quality system
- ISO 9001:2015
- Offices
- 8 across India
- Support
- In-house application engineers
Measuring a linear axis or cylinder?
Tell us the stroke, required accuracy, output and mounting space. Our engineers will suggest a draw-wire or magnetic solution.