Lux meter calibration: how often, to which standards, and how
A lux meter measures illuminance, the luminous flux falling on a surface per unit area, expressed in lux or foot-candles. It is used to verify workplace lighting levels, emergency lighting, and lighting design compliance. The silicon photodetector and its V(lambda) correction filter age and drift over time, so periodic calibration against standard lamps is needed to keep readings trustworthy.
Also known as: light meter, illuminance meter, luxmeter, illumination meter, photometric light meter
How often should a lux meter be calibrated?
Where this number comes from
No standard mandates a fixed interval; ISO/CIE 19476 and DIN 5032-7 define performance classes and test methods but leave recalibration frequency to the user. Most light meter suppliers recommend annual calibration as a starting point, with an allowable tolerance for change over the cycle; the interval is then shortened or extended from drift history, per the ILAC-G24 approach.
Calibration intervals are a risk-based decision for the instrument owner, not a fixed rule: guidance documents such as ILAC-G24 and OIML D 10 describe how to set and adjust them from usage, criticality and calibration history. Treat the interval above as a starting point for your own quality system, not a compliance requirement.
What shortens or lengthens the interval
- Photodetector and V(lambda) filter aging, which causes gradual sensitivity drift that accumulates from year to year
- Exposure to UV, heat, and humidity, which accelerates degradation of the photometric correction filter
- Use for regulatory compliance measurements such as workplace or emergency lighting surveys, where results must be defensible
- Portable field use with frequent handling and transport versus stationary laboratory use
- As-found calibration history: units repeatedly found in tolerance can justify extending the interval, per ILAC-G24 methodology
Standards relevant to lux meter calibration
Defines quality indices (such as spectral mismatch f1'), measurement procedures, and standard calibration conditions for illuminance meters
German standard defining accuracy classes and performance requirements for illuminance and luminance meters, commonly referenced on lux meter datasheets and calibration certificates
Standards are referenced by designation and title. For normative requirements, always work from the current edition of the standard itself.
How a lux meter is calibrated
A typical lux meter calibration, in an accredited lab or in-house, follows this outline. The exact points, tolerances and paperwork come from the applicable standard and your own procedure.
- Inspect the meter and detector head, then allow warm-up and stabilization before measurements
- Perform a zero check with the dark cap fitted and verify the display reads zero
- Set up a NIST-traceable luminous intensity standard lamp (tungsten, 2856 K, CIE Illuminant A) on a photometric bench with baffles to control stray light
- Generate known illuminance levels using the inverse square law by setting calibrated lamp-to-detector distances, or compare directly against a reference photometer
- Record as-found readings at multiple points across each range (for example 10 to 90 percent of full scale) and check linearity
- Compare errors against the meter's class limits (DIN 5032-7 / ISO/CIE 19476) or the manufacturer's accuracy specification
- Adjust if the design allows, record as-left readings, and issue a certificate with measurement uncertainty
Reference equipment typically used
- Luminous intensity standard lamp (tungsten-halogen, 2856 K) with NIST-traceable calibration
- Photometric bench with calibrated distance scale and stray-light baffles
- Precision DC power supply and current shunt for stable lamp operation
- Reference photometer or illuminance meter of higher accuracy class
Tracking lux meter calibrations in a spreadsheet?
Gaugelog is calibration management software for quality managers who’ve outgrown Excel: instrument register, schedules, due-date alerts and certificates in one place. It launches in 2026. Until then, you can generate a clean calibration certificate PDF with our free tool, no account needed.
Sources
- ISO/CIE 19476:2014, Characterization of the performance of illuminance meters and luminance meters, ISO/CIE
Existence and scope of the performance characterization standard, quality indices, and standard calibration conditions
- Why Calibrate Your Light Meter, International Light Technologies
Backs the interval claim: most light meter suppliers start with a recommendation for an annual calibration and provide an allowable tolerance for change during the cycle, with the interval then adjusted from drift history
Cite this data
Gaugelog Calibration Interval Reference, v1.0 (July 2026). 68 instrument types, 236 verified sources. Licensed CC BY 4.0.
Download as CSV or JSON. Intervals are typical starting points, not compliance requirements; every row cites its sources.
The interval on this page is one row of the dataset. Browse all 68 types on the calibration interval reference.