Slimline short-stroke linear position sensor in race car clutch

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With a housing diameter of just 19mm, customised stroke range of anything from 2mm to 50mm and linearity to +/- 0.25 per cent, Positek’s P118 series pushrod style linear position sensors are well suited to precision measurement tasks where space is at a premium and where durability, reliability and affordability are key factors.

Slimline short-stroke linear position sensor in race car clutchAs part of a wide range of linear, rotary and tilt position sensors featuring Positek’s own patented non-contact measurement technology, the P118 series is well proven in arduous industrial applications and for the Team Bath Racing’s 2019 competition race car the diminutive sensor was a great fit for a closed-loop hydraulic clutch application.

Each university year the Team Bath Racing (TBR) students are tasked to build and race a new car to challenge in the worldwide single-seater Formula Student Competition. Over the years the team’s success has extended not just to the actual racing but also prizes for sustainability, design and business management as part of a high-performance team in a competitive environment. The 2019 car saw TBR develop a new hydraulic clutch that included precision position feedback as part of its closed-loop hydraulic system.

Mounted on the race car, the clutch is subjected to the extreme shock and vibration loads associated with motorsports as well as race track temperature, humidity and weather extremes. In both performance and track test modes complete reliability is essential. The clutch design also required that the measurement sensor be installed in the smallest possible envelope with minimal weight an important factor. TBR developed a design that effectively isolated the P118 from the extreme temperature levels inherent with dynamic clutch operation but still required a generous working temperature range and IP67 sealing as a minimum for dependable operation.

BTR specified the flange mounted version of Positek’s P118 with the 4…20mA output option managed within the race car’s control system - converting the linear position of the LVDT to a linear output proportional to the clutch displacement. With housing and connected parts in stainless steel as standard the sensor performance met and exceeded all of the performance specifications required.

Other mechanical options available for the P118 series include body clamp mounting and spring-loaded pushrod with a wider operating temperature range of -40 to +125degC for the 5V input version. 24V DC nominal input versions are also available with output options including 4–20mA and 0.5–9.5V DC.

Part of the Variohm Group, Positek Limited is an ISO9001:2015 certified designer and manufacturer of linear, rotary and tilt sensors with several specialist quality standard certifications including ATEX, IECEx, and CSA for both position sensors and galvanic isolation amplifiers. With its own non-contact inductive position sensor technology, the specialist enjoys a high reputation for a fast-turnaround standard range as well as customised sensors and transducers that are extensively used in intrinsically safe, hazardous, automotive, submersible and other challenging environment measurement tasks.

Full details of the P118 series can be found here and general information across the full Positek range at

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