Affiliations: [a] Department of Rehabilitation Sciences, University of Hartford, West Hartford, CT, USA | [b] Veterans Affairs Cooperative Studies Program, VA Connecticut Healthcare System, West Haven, CT, USA | [c] Yale School of Public Health, Yale University, New Haven, CT, USA
Correspondence:
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Corresponding author: Barbara Crane, University of Hartford, West Hartford, CT 06117, USA. Tel.: +1 860 768 5371; Fax: +1 860 768 4558; E-mail:bcrane@hartford.edu
Abstract: BACKGROUND: Arrays of force sensitive resistors are useful tools for
measuring contact pressures, and are widely used in application to the
wheelchair seating interface. Naturally, arrays with more sensors provide
greater information content; however, operational costs increase steadily
with the number of sensors. OBJECTIVE: Here we provide a first answer to the question: ``How many
sensors are necessary for accurate pressure mapping?'' METHODS: We simulate an ultra-high-density sampling of interfacial pressures
(equivalent to a 121 × 121 array), and incrementally down-sample the data
(down to a 5 × 5 array). At each simulated sampling density, we calculate
three common features (average pressure, maximum pressure, and pressure
gradient). Using data collected from a broadly inclusive population of
wheelchair users (N= 22), we set a threshold of 90% accuracy of feature
extraction for 50% of the population (τ μ ) and for 80% of
the population (τ σ ); data were collected using a
commercially available mat with typical sensor spacing. RESULTS: We find that τ μ ranged from 9-11 sensors on edge (i.e.
9 × 9 to 11 × 11 grid required to faithfully reproduce the three extracted
features), and τ σ ranged from 13-20. CONCLUSIONS: The common 16 × 16 sensor arrays with approximately 3 cm spacing between
sensors, are particularly reliable with high fidelity to grids of higher
sampling density, with the possible exception of pressure gradient, which is
only moderately accurate, and may require a larger sampling density (20 × 20).
