Lux meters and UV meters

Lux meters and UV meters are instruments for measuring illuminance (lux) and UV/UVA/UVC irradiance, used in a wide range of industrial, construction, safety, health and research applications. Lux meters quantify the illuminance of lit surfaces, a parameter governed by the directives on the lighting of work environments (UNI EN 12464) for wellbeing and productivity. UV meters measure ultraviolet irradiance, essential for UV-C sterilization applications (hospitals, food industry), for verifying UV curing lamps (printing, UV-curing coatings) and for safety in environments with UV exposure (industry, welding, sports facilities).

Lux meters

Lux meters use a silicon photodiode fitted with a V(λ) filter – a correction filter that approximates the response of the human eye under photopic conditions – to measure illuminance expressed in lux (1 lux = 1 lumen/m²). The typical range is 0.1 to 200,000 lux, with a resolution of 0.1 lux at low values and an accuracy of ±3-5% of the reading on professional models. The probe is generally separate from the readout unit and connected by a cable, to make measurement easier at precise working positions. Datalogger models record how illuminance varies over time, for analyzing daylight levels in buildings (including the contribution of natural light).

Lighting standards

The UNI EN 12464-1 standard (lighting of indoor work places) prescribes the minimum illuminance values for each type of activity: 100-300 lux for circulation areas and warehouses; 300-500 lux for general offices; 500-750 lux for precision work; 1000-2000 lux for very high precision work (watchmaking, microelectronics). UNI EN 12464-2 governs outdoor lighting. Illuminance checks are an integral part of workplace safety inspections (Italian Legislative Decree 81/2008) and of the commissioning of new lighting installations. Measurements are taken once the lamps have stabilized (at least 30 minutes after switch-on), with the sensor positioned at the height of the working plane.

UV meters

UV meters use photodiodes with optical filters specific to each UV band: UVA (315-400 nm, the “black light” band used for fluorescence); UVB (280-315 nm, the sunburn band); UVC (100-280 nm, the germicidal band used for sterilization). The sensors are calibrated in units of intensity (mW/cm² or W/m²) or of cumulative dose (mJ/cm² or J/m²) – the latter being essential for sterilization applications, where the germicidal dose requires specific exposure times. Professional models come with interchangeable probes for the different UV bands, metrologically calibrated.

UV applications

UV applications are wide-ranging: UV-C sterilization in hospitals, clinics and operating theaters (with verification of the germicidal dose actually applied); surface sterilization in the food industry; drinking water treatment (with verification of the UV dose); UV curing of industrial coatings, inks and adhesives (with monitoring of UV-A lamp intensity); the printing industry (for UV-curing inks); monitoring of work environments with UV exposure (arc welding, industrial processes); Wood’s lamp inspections (fluorescence) for NDT penetrant testing, identification of traces at crime scenes and document verification.

Reference standards

The reference standards are: UNI EN 12464-1 and 12464-2 (lighting of work places); UNI 11142 (lighting measurements); ISO 8995 (lighting of indoor work places, international); IEC 62471 (photobiological safety of lamps); ICNIRP (UV radiation exposure limits for occupational safety). Periodic calibration of lux meters and UV meters is carried out with standard calibration sources certified to ISO 17025; the typical interval is annual.

Selection criteria

The choice of lux meter or UV meter depends on the application: for illuminance checks in work places → a lux meter compliant with UNI EN 12464; for industrial UV curing → a dedicated UVA meter; for sterilization → a UVC meter with dose measurement; for safety applications → instruments with configurable alarms. Range, accuracy, portability, data connectivity and ISO 17025 calibration are decisive criteria for the choice.