Magnetostrictive Position Sensors

Measuring principle of displacement measurement with linear sensors
Displacement sensors convert linear movements into electrical signals. Here, a push rod or a guided or loose actuator is used to mechanically move along the travel distance linearly. In the displacement transducer, the mechanical measuring displacement is detected electrically via a sensor element (electrical measuring path) and converted into electrical signals. The electrical signal acquisition depends on the measuring principle and the sensor technology. The acquired signals are transferred either as analogue signals directly for further processing or via an internal signal conditioning (measuring amplifier / measuring transducer) to a measuring transducer. These signals represent the recorded measurement path. Displacement measuring systems are used in all areas of industry and medical technology. They are used wherever linear mechanical movements are converted into electrical signals for further processing of control tasks, distance measurements and position detection.

Displacement sensor technologies
For linear displacement measurement, displacement sensors are available in five different measuring principles:
Linear potentiometer with a 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. For this purpose, the linear potentiometer has three connections. Two for the resistor and one for the pickup. Application examples are injection molding machines, pneumatics, as well as simple presses.

Features:
Simple sensor principle mostly without electronics
Measured value is available immediately
Resolution almost infinite
Inexpensive and very many differentiated designs
Works with low voltages (hardly any power consumption)
Works with wear
Sensor property changes during operation
Insensitive to interference magnetic fields

Magnetostrictive
The sensor consists of a robust housing, a waveguide inside, a permanent magnet that deflects the generated pulses and a transducer that converts the returning oscillations into an electrical signal. As a result, the position of the magnet is determined using magnetostriction. Examples of applications include injection molding machines, hydraulic cylinders, presses, tank level measurement, and rolling mills.

Features:
Sealed sensor (high IP protection) with electronics.
Contactless measuring principle
Maintenance and wear-free
Durable, consistent accuracy
Long measuring ranges up to 4000 mm
Insensitive to shock and vibration
Resistant to high pressure, ideal for hydraulically moved axes
Insensitive to various chemical media
Sensitive to magnetic interference fields

Inductive (LVDT)
The LVDT is an analog sensor in which a coil system operates - made up of a primary coil and two secondary coils. These coils convert the linear motion into electrical signals. Examples of applications are probes, quality monitoring, automatic production machines, as well as machines for food production.

Features:
Sealed sensor (high IP protection) with or without electronics.
Very good linearity
Recording of small measurement changes
Resolution almost infinite
Long life, consistent accuracy
Maintenance- and wear-free
Suitable for high dynamics
Zero point is reproducible
Signal output absolute
Insensitive to various chemical media
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 measurement path. Application examples include position sensing in elevators or hinges, and applications where space is limited.

Features:
Contactless measuring principle
Maintenance and wear-free
Durable, consistent accuracy
Reliable measurement even under vibration
Detection of wire breaks and short circuits
Sensitive to magnetic interference fields

Optoelectronic
A glass scale is located at the end of the push rod. The transmitter and receiver are arranged opposite each other. The glass scale moves between them. Electrical pulses are converted into light pulses by the transmitter and into electrical signals by the receiver. The downstream amplifier compares the received signal with a predetermined switching wave. Exact positions can be detected with the optical probes. Application examples are probes, quality monitoring, dial gauges, as well as applications in precision mechanical engineering.

Features:
Precise sensor with electronics
Contactless measuring principle
Maintenance and wear-free
Durable, consistent accuracy
Very high resolution
Temperature stable
Easy mounting
Insensitive to interference magnetic fields
The glass scale is fragile

Electrical interfaces and signals
To serve a variety of applications in a wide range of 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 measuring system, signal processing is always integrated after the transit time measurement. The electrical connection is made via 5, 6 or 8-pin plugs with screw thread M12 or M16. Some sensors have a molded cable with a length of one meter (standard) or up to 15m on request. In addition, these sensors offer analog outputs in voltage or current for direct measurement of displacement and velocity or digital outputs.

Optoelectronic
Incremental displacement measurement outputs the count pulses in TTL, OC or LD level.

Mechanical interfaces
Guided push rod with mechanical interfaces
With spring return as prob
With ball joints - ideal for compensation of lateral misalignment
With threaded coupling (with or without return spring)

Loose push rod
For LVDT sensors only - 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 an appropriately matched interface.

Loose carriage (actuator/cursor)
The carriage is moved at a defined distance above the surface of the displacement sensor, the application requires an appropriately tuned 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 "protrudes" horizontally in both directions of the sensor housing. This offers greater robustness for miniaturized displacement sensors because the push rod is safely guided linearly in both plain bearings. There is also no need for structurally complex bearings.
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 push rod its stability.

Mounting
Depending on the product and application, we offer a wide range of accessories for mounting. Many of them are already included with the sensor. Please also refer to our notes on the data sheets. Basically, each sensor requires a clean and flat support surface. For longer measuring distances, additional support should be considered to prevent deflection. Please do not apply mechanical stresses to the sensor housing. Many sensors already come with mounting or clamping brackets. Some have mounting blocks, flanges or ball joints.