L defines the percentage of lumens compared to the initial lumens.

This means that the luminous flux of the luminaire that has been operating for a period of time is compared to the initial luminous flux of the luminaire. L70 means that the flux is reduced to 70% of the original flux, L80 means that it is reduced to 80%, and L90 means that it is reduced to 90%.

B value represents the fault data at data L.

B10 indicates that 10% of leds cannot meet the requirements.

Thus, the LB value represents the actual life of an hour.

L/B is the standard definition of lamp life

For example, 50000h(L90/B10) means that it takes 50000 hours for 10% of the product‘s luminous flux output to drop below 90% of the initial value.

Conversely, it means that LED products have the reliability of light decline less than 10% after 50,000 hours of work.

TM21

Tm-21: It is mainly combined with LM80 report and ISTMT report to calculate the life of the whole lamp.

TM21 provides processing methods for the measured data of LM80, mainly including the following contents:

A. Data fitting method in the form of exponential function is presented.

B. The modification method of fitting life (70% optical decay life) is given.

C. The detailed expression method of life is given.

D. The interpolation method for calculating the life at the given temperature is given.

In Situ Temperature Measurement Test (ISTMT) is the Measurement of LED source box Temperature In LED system (lamp or lamp). Simply put, it is the temperature of the LED inside the lamp. Measurements must be made in accordance with the temperature measurement point (TMP) indicated by the LED package manufacturer.

The ISTMT report is the temperature rise test report