Linear position sensors

The available measuring ranges of displacement sensors and transducers depend on the measurement principle and the respective product series. Althen offers solutions for very small linear movements in the millimeter range up to long measuring distances of several meters. For short and precise measuring ranges, LVDT displacement transducers, inductive displacement sensors, Hall sensors, or linear potentiometers are suitable, for example. For larger strokes and long linear movements, draw-wire sensors or magnetostrictive position sensors are often used. Althen draw-wire sensors enable measuring lengths of up to 50 m, while other displacement sensors, depending on the design, cover measuring ranges from a few millimeters to several hundred millimeters or more. The appropriate measuring length depends on the application, installation space, accuracy requirements, environmental conditions, and desired output signal.

The available resolutions of displacement sensors and transducers depend heavily on the measurement principle, measuring range, output signal, and evaluation electronics used. LVDT displacement transducers can detect very small changes in displacement and offer virtually infinite resolution. Depending on the design, Althen linear incremental encoders achieve resolutions down to 2.5 µm. Draw-wire sensors are available with long measuring ranges of up to 50,000 mm; Althen specifies an accuracy of up to 0.01 mm for these. Other measurement principles such as inductive, magnetostrictive, Hall-effect, eddy-current, or potentiometric displacement sensors offer different resolutions depending on the product series and are suitable for various requirements regarding precision, robustness, and measuring range. For the correct selection, resolution and accuracy should always be considered together. Measuring range, repeatability, linearity, signal processing, installation, and environmental conditions are also decisive.

Depending on the measurement principle and product series, displacement sensors and transducers are suitable for different temperature ranges. Many industrial versions are designed for harsh environments and offer high temperature resistance, robust housings, protection ratings up to IP69K, and resistance to environmental influences. The specific temperature range must always be checked in the data sheet of the respective sensor. PR-series LVDT displacement transducers, for example, are designed for -40 °C to +125 °C, with higher temperatures available as an option. Inductive displacement transducers offer particularly stable temperature behavior, while magnetostrictive position sensors are largely insensitive to temperature, shock, vibration, and contamination. In addition to ambient temperature, temperature fluctuations, installation conditions, protection rating, humidity, vibrations, and the required measurement accuracy should also be considered when selecting a sensor. We will be happy to help you select a suitable displacement sensor or transducer for your application.

Displacement sensors and transducers are evaluated differently depending on the measurement principle and output signal. They often provide an analog signal, for example resistance, 0–10 V, 0.5–4.5 V, or 4–20 mA. These signals can be processed by a control system, display, measuring amplifier, or data acquisition system. Other displacement sensors provide digital or incremental signals, for example pulses, SSI, CANopen, or other interfaces. Incremental sensors detect changes in position and usually require referencing, while absolute sensors can provide the position directly after power-up. For reliable evaluation, the appropriate output signal, correct supply voltage, suitable signal conditioning, clean wiring, and stable mechanical installation are essential.

Displacement sensors and transducers should be recalibrated when consistently high measurement accuracy must be demonstrated or when operating conditions may affect the measurement signal. Typical reasons include regular quality or measuring-equipment monitoring, intensive use, strong vibrations, temperature changes, mechanical loads, repairs, or component replacement. A fixed calibration interval depends on the sensor type, application, required accuracy, and internal quality specifications. In many industrial applications, an annual inspection is recommended; shorter intervals may be appropriate for safety-critical test benches, high levels of use, or tight tolerances. The measurement chain should also be checked and, if necessary, recalibrated after a new installation, noticeable measurement deviations, or changes to the mechanics, cables, signal conditioning, or control system. Further information on calibration can be found on our website.

The service life of displacement sensors and transducers depends strongly on the measurement principle, mechanical loading, and environmental conditions. Althen offers displacement sensors with high robustness, protection ratings up to IP69K, resistance to environmental influences, and long service life. Contactless sensors such as LVDT, inductive, magnetostrictive, Hall-effect, or eddy-current sensors are generally particularly durable because there is no mechanical sliding contact subject to wear. Thanks to their contactless design, LVDT sensors minimize wear and are therefore well suited to continuous operation and demanding environments. Inductive displacement transducers are also contactless, highly wear-resistant, robust, and durable. For contact-based sensors such as linear potentiometers, service life is usually specified in measurement cycles. For applications involving frequent movement, Althen lists models with more than 50 million measurement cycles; some versions achieve up to 100 million cycles, for example LPC, SLPT, or ELPH. The actual number of years a sensor lasts depends on factors such as movement frequency, stroke, speed, lateral forces, temperature, humidity, vibrations, protection rating, and installation. We will be happy to help you select a suitable displacement sensor or transducer — contact us!