Light source modulation characterisation

Flicker400 from Bentham

The Flicker400 offers lamp and luminaire manufacturers deeper insight into the flicker characteristics essential in development of high-quality novel lighting, increasingly relevant for those featuring dimming control.

Features

Windows control software (BenWin+) provides full automation via USB 2.0
Setup comprises a DH400-VL v-lambda detector, ORM400 photometric detector, the 477 and the USB Digital Scope

Further information

Comprising a close-match photometric detector, high-speed amplifier and data acquisition, the Flicker400 provides high-accuracy flicker percent, frequency and index assessment in a straightforward, highly repeatable procedure.

Whilst the photobiological impact of flicker is still widely debated, the implications for image recording equipment are undeniably apparent and of increasing significance with the continued adoption of SSL in studio and stadium environments.

Core benefits

Simple establishment of all key flicker metrics
Stay ahead of the legislative curve
Easy integration into existing photometric testing facilities
Quickly gain insight into source performance

Reported parameters

Percent flicker
Flicker index
Flicker frequency

Specifications

Photometric detector/ ORM400

Spectral function	CIE 1924 V(λ) Spectral Luminous Efficiency Function for Photopic Vision
Spectral response range	380-780nm
Photopic match, f1	<3%
Angular response, f2	<1.5%
Linearity, f3	< .2%
Typical responsivity	5x 10^-10A/lux
Calibration traceability	Physikalisch-Technische Bundesanstalt (PTB, Germany)
Diffuser diameter	7mm
Stray light suppression	Variable aperture baffle tube
Connector	BNC
Amplifier gain ranges	10¹⁰-10⁵ V/A
Maximum input	100µA
Input impedance	Virtual ground
Gain accuracy & stability	±1 %, 200 ppm/ °C
Output stability	5-500 ppm/ °C dependent on gain range
ADC resolution	4 ½ digit BCD (0 to 19999) (>14 bit resolution)
Luminous intensity range	0.01D2-200000D2 (D photometric distance (m))

477 - AC Current pre-amplifier frequency response

V/A	Bandwidth (-3Db)
10³	>1MHz
10⁴	1MHz
10⁵	260kHz
10⁶	30kHz
10⁷	23kHz
10⁸	4kHz

General

Power supply	PMC MAC ORM400
Interface	USB 2.0

System requirements

Component	Current (220V) (A)
ORM400	<0.1
Total	<0.1

Applications

Over the past year, reports have demonstrated that some SSL systems, particularly those paired with dimming controls, demonstrate significant photometric flicker, thought to cause photosensitive epilepsy, migraines, headaches, eye strain and non-specific malaise. Whilst the photobiological impact of flicker is still widely debated, the implications for image recording equipment are undeniably apparent and of increasing significance with the continued adoption of SSL in studio and stadium environments.

Definition and sources of flicker

Flicker is the term used for the rapid and repeated modulation of light output from a source. The principle source of flicker is the periodic variation in AC mains operated lamp output, at twice the AC frequency. Once an issue with fluorescent tubes with magnetic ballasts, flicker has largely been forgotten until recently, when the effect of SSL lamp drive circuitry and phase-cut dimming circuits have caused concern once again.

Potential effects of flicker

The health effects of flicker are generally divided into those due to visible flicker and those due to invisible flicker. In the visible domain, frequencies in the range ~3 to 70Hz represent a risk of seizure in those with photosensitive epilepsy, whilst in the invisible domain, at higher frequencies, migraines, headaches, eye strain and non-specific malaise may result.

Quantifying flicker

Two metrics are currently defined for the evaluation of flicker, percent flicker, and flicker index, the latter being generally preferred since it takes account of difference in waveform shape or duty cycle. As standards for the evaluation of flicker are developed, account may also be taken of flicker frequency.

ENERGY STAR® Method of measurement for light source flicker

California Energy Commission Appendix JA10
1789-2015 - IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers
UEFA Stadium Lighting Guide 2016
CIBSE LG04 Lighting Guide 04: Sports Lighting - LG4
ASSIST recommend Recommended Metric for Assessing the Direct Perception of Light Source Flicker, Volume 11, Issue 3 (ASSIST 2015)