Cable extension transducers in crash test dummies

What are cable extension transducers?

Cable extension transducers are linear position sensors. They use a spring-loaded coil and a cable to measure linear position. With this pre-tensioned, non-stretchable cable, which is pulled out or retracted during position changes, they can convert free movements in space into a rotational movement, which is then transformed into an electrical signal with the help of a rotational angle sensor.

They are not only convincing in their easy handling, which allows paths and movements of objects to be measured, the installation is also effortless - even in very tight and difficult-to-access areas - as they do not require a perfectly parallel alignment.

However, the biggest advantage over linear potentiometers and other alternatives is the compactness of the cable extension transducer. In relation to size and measuring length, the sensor itself can remain surprisingly small while the cable can be several meters long.

Cable extension transducers in crash test dummies

Cable extension transducers are well suited for use in crash test dummies. Important conclusions about the safety of tested vehicles can be drawn from the deformation values of the dummies. Designers can precisely determine where optimisations need to be made, for example, in the design or interior, to guarantee the safety of the occupants based on the deformations.

Various types of sensors are installed in crash test dummies. To obtain realistic deformation values, cable extension transducers are primarily placed on the chest, spine and pelvis, as well as the head and legs. These body parts are given special attention during the tests. Although space is limited, even such tight areas are not a problem for compact cable pull sensors. They can withstand extreme accelerations, follow them quickly, and thus deliver precise measurement results even under challenging conditions.

Variohm's cable pull sensors

For applications such as these, Variohm, for example, offers the M150 cable extension transducer. The basic advantage of this model is that the movement to be registered can be captured freely and without exact alignment of the moving components. Moreover, the M150 is currently the smallest cable extension transducer in the world as a position sensor with a 19 mm edge length. The sensor, which works according to the potentiometer principle, reliably detects position changes and paths with an accuracy of ±1.0%. It can be used in a temperature range of -40°C to +85°C.

Cable extension transducers are versatile and can be used in various other fields, such as robotics, the automotive industry, and aerospace. Variohm Eurosensor offers a wide range of robust cable extension transducers. These sensors are available as individual pieces upon request or in bulk for OEMs. Measurement ranges are available from 38 mm to 43 m, with the larger measurement ranges being part of the industrial line for heavy-duty applications with protection up to IP68.