A draw wire encoder is a sensor that accurately measures linear displacement by converting the movement of a cable into an electrical signal that can be monitored, recorded, or analysed. These devices are used across automotive testing, aerospace, manufacturing, structural engineering, and research — anywhere that requires reliable, repeatable measurement of linear motion.
The operating principle
A flexible cable attaches to the object being tracked. As the object moves, the cable extends or retracts, turning a spool or drum inside the device. This mechanical motion translates into an electrical signal representing position or distance travelled. The output can be analogue — voltage or current — or digital, making draw wire technology compatible with modern control systems and data acquisition platforms. That versatility covers applications from laboratory experiments to industrial automation.
Key components
The retractable cable, typically stainless steel or high-strength polymer, guides onto an internal spool with minimal stretch and friction — critical for accuracy over repeated use. The spool connects to a rotary encoder that converts drum rotation into an electrical signal. Depending on the model, this can be incremental (providing relative displacement) or absolute (giving a fixed position reference).
Modern draw wire sensors incorporate on-board electronics for noise filtering, signal amplification, and interface options including 4-20mA, 0-10V, and digital pulses. The processed signal feeds into PLCs, SCADA systems, or bespoke monitoring solutions.
Installation and environmental considerations
The sensor must be aligned along the path of movement and the cable kept straight without kinks or excessive tension. Many high-quality models are rated IP65 or higher, allowing operation in dusty, wet, or vibration-prone industrial environments.
Typical applications
Draw wire encoders are used for hydraulic cylinder monitoring, crane and hoist positioning, structural deflection measurements, lab testing rigs, and mobile machinery feedback. Their ability to provide long-range, precise measurement in a compact, durable package makes them adaptable across a wide range of sectors.
Wherever accurate linear measurement is required, draw wire encoders enable better data collection, operational control, and informed decision-making. Sensors UK Ltd supplies high-quality draw wire encoder solutions across the UK and internationally. Contact us for technical guidance and tailored recommendations: sales@sensorsuk.com or 01727 859373.
