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Introduction to flicker standard terms

time:2022-02-11

1.BASIC    

Frequency:Frequency here is the frequency of light output of a tested lighting product. 

Flicker Index:(Reference:IESNA 2000) 

Flicker Index is defined as the area between the curve representing the waveform and the average light  level  divided by the total area below the curve for a single cycle of the fluctuation. 

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Percent Flicker and Modulation Depth(Reference:CIE TN 006:2016 and IEEE Std 1789:2015) 

Percent Flicker or modulation depth is defined as the difference between maximum and minimum light level divided by the sum of maximum and minimum light level(multiplied by 100%). 

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2、IEEE Std 1789 

(Reference:IEEE Std 1789-2015:IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers) 

NM is the abbreviation of normalized modulation,and is used to evaluate the risk level of flicker. 

NM1=1 represents the limit value of High-Risk Level; 

NM2=1represents the limit value of Low-Risk Level . 

  

3、IEC-Pst 

(Reference:IEC TR 61547-1:2015 Equipment for general lighting purposes-EMC immunity requirements:part 1-An objective voltage fluctuation immunity test method ): 

 Pst here is the measured parameter to quantify the flicker of lighting products,which is proposed by IEC TR 61547-1 depending on IEC61000-3-3,IEC61000-4-15,etc. 

Pst=1 represents the average observer just feel the flicker with the probability of 50%. 


4、CA CEC 

(Reference:Joint Appendix JA10-Test Method for Measuring Flicker of Lighting Systems and Reporting Requirements) 

This test method measures the fluctuation of light from lighting systems and processes this signal to quantify flicker as a percent  amplitude modulation (percent flicker) below a given cut-off frequency. 

 Percent Amplitude Modulation is defined as the difference between maximum and minimum light level divided by the sum of maximum and minimum light level for a given dimming level.  


5、ASSIST 

These parameters refer to the flicker recommendations of the Alliance for Solid-State Illumination Systems and Technologies published by US Light Research Center: 

1) Flicker Parameters for Reducing Stroboscopic Effects from Solid-state Lighting systems; 

2) Application Considerations Related to Stroboscopic Effects from Light; 

3) Recommended metric for assessing the direct perception of light source flicker. 

①Flicker: 

A.Perceptual Modulation:Mp 

Mp=1 corresponds to threshold detection (50% detection rate); 

B.Flicker detection probability:DP 

DP=50% corresponds to Mp=1. 

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                                    Relation between flicker detection probability and the metric value 

②Stroboscopic Effects: 

A.Percent likehood of detection of Stroboscopic Effects:d 

The percent likehood of detection of stroboscopic effects can be estimated by using the frequency and percent flicker. 

B.Acceptability of Stroboscopic Effects: 

Borderline frequency fb:the frequency corresponding to the borderline between acceptability and unacceptability for a given percent flicker value. 

a:It is used to estimate the acceptability of Stroboscopic Effects for a given flicker frequency and using the borderline frequency fb. 

a=+2 Very acceptable; 

a=+1 Somewhat acceptable; 

a=0 Neither accepable nor unacceptable; 

a=-1 Somewhat unacceptable; 

a=-2 Very unacceptable. 


6、CIE SVM 

(Refers to CIE TN:006-2016:Visual Aspects of Time-Modulated Lighting Systems-Definitions and Measurement Models)  

SVM is proposed by CIE for measuring Stroboscopic effect,which have also been recommended by Lighting Europe and NEMA. 

SVM=1 Just visible,this means that an average observer will be able to detect the artefact with a probability of 50%); 

SVM<1 Unvisible; 

SVM>1 Visible. 


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