Things to know about displacement sensors
Guide for Linear Sensors
Linear Sensors
Linear potentiometers, magnetical and optical linear transducers and measuring probes
Our displacement sensors have an optimal focus on space-saving, robustness and precision. With our linear sensors you can measure mechanical measuring distances up to 4000 mm. A wide selection of mechanical and electrical interfaces allows the best possible constructive and electrical integration into your application.
We cover high demands in protection class, EMC, shock, hydraulic pressure (up to 350 bar), accuracy (up to 1 µm) and measuring dynamics (up to 10 m/s @ max. 100 m/s²). Applications with an operating temperature range up to 600°C can also be realized.
Each measuring principle has its own advantages, which we will determine with you during our consultation. Only the requirements of the application determine the choice of the suitable displacement transducer. In many cases, demanding applications require technical product adaptation. MEGATRON is your specialist for this adaptation process - even for small quantities.
Index
Measuring principle of linear sensors
The task of displacement sensors is to convert linear movements into electrical signals. To do this, a push rod or a guided or loose actuator is used to mechanically move along the travel distance in a linear manner.
In the displacement transducer, the mechanical measuring path is electrically detected via a sensor element (electrical measuring path) and converted into electrical signals. The electrical signal acquisition depends on the measuring principle or sensor technology. The acquired signals are either transferred as analogue signals directly to a transducer for further processing or via an internal signal conditioning (measuring amplifier / transducer).
These signals represent the recorded measuring path. Displacement measuring systems are used in all areas of industry and medical technology. Just where linear mechanical movements are converted into electrical signals for further processing of control tasks, distance measurements and position detection.
Linear sensor technologies
For linear displacement measurement, linear sensors are available in five different measuring principles:
- Linear potentiometer with potentiometric resistance element
- Magnetostrictive technology
- Inductive technology (LVDT)
- Hall effect technology
- Optical probes with optoelectronic sensor technology
Potentiometric
A linear potentiometer is a passive component whose resistance value can be continuously adjusted. The wiper is guided over the resistance track, which outputs the resistance value depending on its position. The linear potentiometer has three connections for this purpose: two for the resistor and one for the pickup.
Application example: injection moulding machine, pneumatics, simple presses
- Simple sensor principle mostly without electronics
- Measured value is available immediately
- Resolution almost infinite
- Reasonably priced and very many differentiated designs
- Works with low voltages (hardly any power consumption)
- But works with wear
- Sensory characteristics change in the course of operation
Magnetostrictive
The sensor consists of a robust housing, a waveguide inside, a permanent magnet that deflects the generated pulses and a converter that converts the returning vibrations into an electrical signal. As a result, the position of the magnet is determined by means of magnetostriction.
Application example: injection moulding machine, hydraulic cylinders, presses, tank level measurement, rolling mills.
- Sealed sensor (high IP protection) with electronics
- Contactless measuring principle
- Maintenance- and wear-free
- Durable, consistent accuracy
- Long measuring distances up to 4000 mm
- Insensitive to shock and vibration
- Withstands high pressures - ideal for hydraulically moved axes
- Insensitive to various chemical media
- But sensitive to magnetic interference fields
Inductive (LVDT)
The LVDT is an analog sensor in which a coil system operates - consisting of a primary coil and two secondary coils. These coils convert the linear motion into electrical signals.
Application example: probes, quality monitoring, manufacturing automation, food production
- Sealed sensor (high IP protection) with or without electronics
- With very good linearity
- Recording of small measurement changes
- Resolution almost infinite
- Durable, consistent accuracy
- Maintenance- and wear-free
- Suitable for high dynamics
- Zero point is reproducible
- Signal output absolute
- Insensitive to many chemical media
- But sensitive to magnetic interference fields
Hall effect
Hall sensors use a permanent magnet placed on a moving plunger. One or more Hall ICs are located on the travel path. They measure the field strength on the path and identify the position of the magnet and thus the distance of the measuring path.
Application example: Position detection in elevators or hinges, where space is limited
- Contactless measuring principle
- Maintenance- and wear-free
- Durable, consistent accuracy
- Reliable measurement even with vibration
- Detection of wire breaks and short circuits
- But sensitive to magnetic interference fields
Optoelectronic
At the end of the push rod there is a glass scale. The transmitter and receiver are arranged opposite to each other. The glass scale moves between them. Electrical impulses are converted into light pulses by the transmitter and into electrical signals by the receiver. This way a glass scale linear encoder is implemented and is the principle of this kind of sensor. The downstream amplifier compares the received signal with a predetermined switching wave. With our optical probes exact positions can be detected.
Application example: Probes, quality monitoring, dial gauges, precision engineering
- Precise sensor with electronics
- Contactless measuring principle
- Maintenance- and wear-free
- Durable, consistent accuracy
- Very high resolution
- Temperature stable
- Easy mounting
- Insensitive to magnetic interference fields
- But the glass scale is fragile
Technology comparison
| Measurement method / Technical requirements | Potentiometric | LVDT | Magnetostrictive | Hall effect | Optoelectronic |
| High resolution (100 μm) | + | + | + | + | + |
| Very high resolution (1 μm) | - | - | + | + | + |
| Operating speed | 0 | 0 | + | + | - |
| Small shape | + | + | 0 | + | 0 |
| High protection class (IP65) | 0 | 0 | + | + | 0 |
| Use in magnetic field | + | - | 0 | - | + |
| Very small measuring distances (±1 mm) | - | + | - | 0 | - |
| Digital processing required | - | - | - | - | + |
| Lateral forces occur (transverse) | 0 | 0 | 0 | - | - |
| High measuring rate/strongly oscillating movements | 0 | + | + | + | + |
Electrical interfaces and signals
To serve a variety of applications in different industries, we offer displacement sensors with corresponding electrical interfaces.
Potentiometric and inductive
Our potentiometric and inductive linear sensors have also been realized with integrated electronics to simplify electronic integration. This allows direct connection to the typical analog signals 0..5 V / ±5 V / 0..10 V / ±10 V / 0..20 mA / 4..20 mA without external amplifier.
Hall effect
Our contactless Hall sensors have an analog output with 0.5..4.5 V. This enables wire break and short circuit detection.
Magnetostrictive
In the magnetostrictive displacement encoder the signal processing after the travel time measurement is always integrated. The electrical connection is made via 5, 6 or 8-pin plugs with M12 or M16 screw threads. Some sensors have a potted cable with a length of one meter (standard) or on request up to 15 m.
In addition, these sensors offer analog outputs in voltage or current for direct measurement of displacement and speed or digital outputs.
Optoelectronic
The incremental displacement measurement outputs the counting pulses in TTL, OC or LD level.
Mechanical interfaces
Guided push rod with mechanical interfaces
- With spring return as probe
- With ball joints - ideal for compensation of lateral misalignment
- With threaded coupling (with or without return spring)
Loose push rod
- Only for LVDT sensors - with threaded coupling - the application requires an appropriately matched interface. Core extensions from 50 mm to 315 mm optionally available
Guided carriage (actuator/cursor)
- Carriage is mechanically or magnetically connected to the displacement sensor, the application requires a correspondingly matched interface
Loose carriage (actuator/cursor)
- The carriage is moved at a defined distance above the surface of the displacement sensor, the application requires a correspondingly adapted interface
There are two types of mechanical integration of push rods in the displacement sensor:
- The push rod is guided on both sides. This means that the push rod "projects" horizontally in both directions of the sensor housing. This offers greater robustness with miniaturized displacement sensors, because the push rod is securely guided linearly in both slide bearings. In addition, there is no need for elaborate bearing arrangements.
- The push rod is guided on one side. This means that the push rod only protrudes on the measuring side. Bearings inside the housing give the connecting rod its stability.
Mounting
We have a wide range of accessories for installation - depending on product and application. Many accessories are already enclosed with the sensor. Please also note our information on the product data sheets.
As a general rule: Each sensor requires a clean and even support surface. For longer measuring distances, additional support should be considered to prevent deflection. Please do not apply any mechanical stress to the sensor housing.
Many sensors are already supplied with fixing clamps. Some have mounting blocks, flanges or ball joints.
- Linear potentiometer with almost infinite resolution
- Space-saving mini design
- Measuring lengths from 8 mm to 15 mm
- Rear and front guided push rod
- Long lifetime
- Compact displacement sensor
- For harsh environmental conditions - protection class IP60
- Mounting by ball joints, mounting brackets or flange
- Long lifetime and accuracy
- Measuring lengths from 25 mm to 300 mm
- Linear potentiometer with almost infinite resolution
- Space-saving compact design
- Measuring lengths from 13 mm to 100 mm
- Also available with spring return probe
- Long lifetime
- For harsh environmental conditions - protection class up to IP67
- Mounting by ball joints, mounting brackets or flange
- Long life span and high accuracy
- Measuring lengths from 10 mm to 300 mm
- Space-saving due to small dimensions
- Long lifespan and high accuracy
- Measuring lengths from 10 mm to 30 mm
- Rear and front guided push rod
- Two M3 threads and 10 mm flange diameter for easy integration
- Compact and robust design
- With front guided push rod
- Available as a probe
- Measuring lengths from 25 mm to 100 mm
- Long lifetime and high accuracy
- Compact industrial design
- With spring-suspended probe tip
- Long lifetime and high accuracy
- Linear potentiometer with almost infinite resolution
- Measuring lengths from 25 mm to 100 mm
- In a compact industrial design
- Front guided push rod and ball joints
- Long lifespan and accuracy
- Linear potentiometer with almost infinite resolution
- Measuring lengths from 25 mm to 200 mm
- For harsh environmental conditions up to IP67
- Coupling with ball joints
- Very long lifetime and very high accuracy
- Measuring lengths from 50 mm to 750 mm
- Space-saving and compact construction
- With external magnetic cursor
- High degree of protection IP67 and operating pressure up to 20 bar
- Measuring lengths from 50 to 1000 mm
- With cable or plug
- Cursor with or without ball joint
- Minimum height only < 7 mm
- Easy mounting
- Flexible mechanical coupling due to universal cursor
- No push rod necessary
- Hermetically encapsulated sensor element
- Sealed round cable outlet
- Saves space by flat construction and by slider coupling
- Integrated end stops
- 3 million sliding movements
- Internal or external flange design
- Space saving design
- Independent linearity ±0.1 %
- Conductive plastic with almost infinite resolution
- Measuring lengths from 50 mm to 550 mm
- Long life span (100 million movements)
- Compact industrial design
- With spring-suspended probe tip or tip with roller bearing
- Long lifespan and high accuracy
- Linear potentiometer with almost infinite resolution
- Measuring lengths from 10 mm to 100 mm
- High degree of protection IP67 and max. 250 bar operating pressure
- With external magnetic cursor - capsule of the sensor element
- Mounting via internal or external flange
- Measuring lengths from 50 mm to 1000 mm
- Long lifetime (up to 100 million movements)
- With integrated signal-converter
- High degree of protection IP67 and max. 250 bar operating pressure
- With external magnetic drag - capsule of the sensor element
- Mounting via internal or external flange
- Measuring lengths from 50 mm to 1000 mm
- Long lifetime (up to 100 million movements)
- High accuracy due to very good linearity
- For hydraulic applications up to 250 bar (peak 400 bar)
- With external cursor - encapsulation of the sensor element
- Mounting via internal or external flange
- Measuring strokes from 50 mm to 1000 mm
- Long lifespan (up to 100 million axis movements)
- Robust design in protection class up to IP67
- Measuring lengths from 50 to 900 mm
- With front guided push rod
- Simple coupling with ball joints (not included)
- For applications with strong vibrations
- Space saving cursor construction
- Easy coupling by link ball on cursor
- Measuring lengths from 100 mm to 2000 mm
- Long lifetime (up to 100 million movements)
- Measurement from 50..1500 mm
- Wear-free measuring principle and absolute analogue signal
- Direct and inverse analog output
- For harsh conditions IP67
- Very flat construction with only 14 mm
- High precision due to high resolution and good linearity
- Electromagnetic compatibility 2014/30/EU (EMC)
- Measuring strokes from 50 mm to 4000 mm
- High IP protection class IP67 and 350 bar operating pressure (peak pressure max. 500 bar)
- Made of stainless steel AISI 316
- With external cursor
- Mounting via external flange (metric / inch)
- Electromagnetic compliance EMC 2014/30/EU
- RoHS 2011/65/EU
- Mech. connection by ball coupling to compensate for the angular offset or free position sensor
- Small space requirement without push rod
- Measuring lengths from 50 mm to 4000 mm
- Very precise due to high resolution and good linearity
- Electromagnetic compatibility 2014/30 /EU (EMC)
- Very accurate measuring principle up to 4000 mm
- Suitable for applications up to 500 bar peak
- For heavy duty applications IP67
- Absolute true power on signal
- For difficult environmental conditions (max IP68 / 30bar)
- Miniature design max. Ø9.5 mm
- Very accurate measuring principle for small measuring strokes
- Measuring strokes from ±0.65 to ±12.5 mm
- Very long lifespan
- Suitable for high dynamics
- On request for temperature ranges up to 600°C
- Very accurate for small measuring strokes (2..50 mm)
- In 2 designs (probe or loose core)
- For harsh environmental conditions (up to IP67)
- Very long lifespan
- Suitable for high dynamics
- Absolute analog signal
- Very accurate measuring principle
- For harsh environmental conditions (up to IP68)
- Very long lifespan
- Suitable for high dynamics
- Absolute analog signal
- Very accurate for small measuring strokes (2..200 mm)
- In 3 designs (ball joints, probe, loose core)
- For harsh environmental conditions (up to IP68)
- Very long lifespan
- Suitable for high dynamics
- In 3 designs (probe, guided push rod or loose core)
- Wide temperature range -50°..125° C
- Very long lifespan due to wear-free measuring principle
- Suitable for high dynamics and oscillating movements
- AC voltage
- High resolution up to 1 µm
- Output channels A, B
- Linedriver, Open Collector or TTL
- High quality ball cage bearing
- Easy mounting on shaft 8h6mm
- Temperaturestable counting pulses because of glass scale
- High resolution up to 5µm
- For 30 mm or 50 mm stroke
- accurate sleeve bearing
- Easy mounting on shaft 8h6mm
- Temperature stable counting pulses because of glas scale
- Long lifespan >100 million movements
- No wear-induced degradation of signal quality
- Reliable measurement even at vibration
- Resolution: 12 bit
- Analog output: 0,5..4,5 V
- Enables wire break detection and short-circuit detection
- Supply voltage: 5 V