Case Study: Plextek
Independent Torque Measurement in Back-to-Back Motor Control Testing
The Client: Plextek
Plextek is a leading technology consultancy, specialising in embedded systems, motor control, software development, control systems engineering, and rigorous test and validation.
Established over 35 years ago in the Cambridge “Silicon Fen”, Plextek works across a diverse range of sectors including health technology, consumer electronics, defence, navigation, and industrial automation, helping clients overcome technical challenges through innovative design and rigorous validation.
For a recent project in the connected fitness sector, Plextek were tasked with developing a custom Field‑Oriented Control (FOC) solution for a BLDC motor system. The controller had to provide low torque ripple for natural resistance and withstand being back-driven by the user, all while integrating into the client’s existing system architecture.
The Challenge
Plextek needed to validate the controller using a custom mechanical testbed in a back‑to‑back configuration, in which two motors operate against each other to replicate realistic loading conditions. This setup allowed them to examine behaviour across both motoring and generating modes, while creating a critical requirement: the ability to measure torque independently between the two machines with high precision.
To achieve the smooth, low‑ripple torque required for the application, Plextek needed a clear view of how the motor behaved under different conditions. This meant being able to detect small variations in torque output and validate the performance-related effects of any modifications. The controller also had to remain stable when back‑driven by the user, making accurate measurement in both directions particularly important.
The Solution
Plextek acquired a Datum Electronics M425 Torque Transducer, widely used in test rigs for its highly accurate bidirectional torque measurement, convenient inline form factor, and stable, low-latency output.
With their rig now outfitted with dedicated torque, temperature, speed, and position sensors, Plextek ran the motor through a series of automated trials, using the captured data to evaluate performance under different loads and control profiles.
The Outcome
Backed by high‑quality data, Plextek could verify that their custom motor controls delivered accurate torque response and reliable operation under real‑world conditions.
By meeting their client’s ambitious torque requirements and native-level integration, Plextek’s demonstrated their multi-disciplinary expertise and delivered a production‑ready solution the client could adopt with confidence.
Learn more about Plextek and their custom motor control solutions at plextek.com.
“The torque transducer gave us clean data to validate the FOC algorithm under real loading conditions. Being able to measure torque independently, and at high precision, meant we could iterate confidently and demonstrate that the controller met specification.”
Head of Software, Plextek
Datum M425
Accurate Inline Torque Measurement for Motor Test Rigs
With an accuracy class of ±0.1%, a compact and inline form factor, and a variety of digital or analogue outputs, the Datum Electronics M425 Torque Transducer delivers reliable, repeatable data for R&D, test rigs, and industrial applications. Its robust, innovative, and flexible design make it easy to integrate into a wide variety of demanding environments.
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