# Multi-Sensor Measurement of Cylindrical Illuminance

## TL;DR

A multi-sensor device is developed to measure cylindrical illuminance, enabling accurate lighting evaluation and analysis.

## Contribution

A prototype multi-sensor device that simultaneously measures horizontal and approximates cylindrical illuminance with high accuracy.

## Key findings

- The prototype accurately approximates mean cylindrical illuminance using multiple vertical detectors.
- The device enables decomposition of the illuminance solid into vector and symmetric components.
- Compared to conventional methods, the multi-sensor approach reduces spatial error and provides richer lighting data.

## Abstract

What are the main findings?
Approximation of cylindrical illuminance using multiple vertical detectors.Prototype of a multi-sensor device for cylindrical illuminance measurements.

Approximation of cylindrical illuminance using multiple vertical detectors.

Prototype of a multi-sensor device for cylindrical illuminance measurements.

What are the implications of the main findings?
Enabling modelling-factor measurement with a single multi-sensor unit.Construction of a two-dimensional cross-section of the illuminance solid.

Enabling modelling-factor measurement with a single multi-sensor unit.

Construction of a two-dimensional cross-section of the illuminance solid.

Spatial light field metrics, such as cylindrical illuminance, provide essential information for qualitative lighting evaluation, yet they remain far less common in practice than horizontal illuminance. To address this gap, we present a multi-sensor prototype that simultaneously measures horizontal illuminance Eh and approximates mean cylindrical illuminance Ez from a set of vertical illuminances uniformly distributed around a cylindrical surface. The device uses a flexible PCB wrapped around a support barrel, along with an inertial and magnetic measurement unit for orientation tracking. The measurements enable direct calculation of the modelling factor defined in the technical standard EN 12 464 and the visualization of the directional light distribution using polar plots and an illuminance solid. Results show that the prototype approximates mean cylindrical illuminance with high accuracy while preserving directional information, allowing the illuminance solid to be decomposed into vector and symmetric components. Compared with conventional approximation methods, the proposed multi-sensor approach reduces spatial error and yields richer data for lighting analysis. These findings indicate that multi-sensor systems can bridge the gap between theoretical spatial metrics and practical photometry and support the improved modelling evaluation and integration of qualitative lighting parameters into routine workflows.