Since the advent of electromyogram recording, precise measures of tremor and gait have been used to study movement disorders such as Parkinson's disease. Now, a wide range of accelerometers and other motion-tracking technologies exist to better inform researchers and clinicians, yet such systems are rarely tested for accuracy or suitability before use. Our inexpensive test-rig can produce sinusoidal displacements using a simple cantilever system driven by a subwoofer. Controlled sinusoids were generated using computer software, and the displacement amplitudes of the test-rig were verified with fiducial marker tracking. To illustrate the use of the test-rig, we evaluated an accelerometer and an electromagnetic motion tracker. Accelerometry recordings were accurate to within ±0.09 g of actual peak-to-peak amplitude with a frequency response close to unity gain between 1 and 20 Hz. The electromagnetic sensor underestimated peak displacement by 2.68 mm, which was largely due to a diminishing gain with increasing frequency. Both sensors had low distortion. Overall sensitivity was limited by noise for the accelerometer and quantisation resolution for the electromagnetic sensor. Our simple and low-cost test-rig can be used to bench-test sensors used in movement disorders research. It was able to produce reliable sinusoidal displacements and worked across the 1- to 20-Hz frequency range.
Keywords: Accelerometer; Electromagnetic; Motion tracking; Movement disorders; Tremor.