LED thermal characteristics parameters means thermal resistance and junction temperature. Thermal resistance means temperature gap along the heat flow resistance division by dissipation power on channel. LED junction temperature is the PN junction temperature LED thermal resistance and junction temperature are important factors to influence on LED optical properties. The purpose of meas-uring and calculating LED thermal resistance is providing LED encapsulation cooling design theory and  practice basis.
The LED junction temperature(JT) heavily influences Vf. Under constant current, the JT increases firstly and reaches thermal equilib-rium after a certain time, the photometric and colorimetric quantities of the LED can only be stable under thermal equilibrium state.

◆ Measuring temperature measurement, thermal resistance, time curve
◆ Measuring LED-IV characteristic curve
◆ Measuring forward voltage /time curve(vt)
◆ LED voltage temperature index K
◆ Measurement standard conditions and the conditions of heat balance thermal resistance, junction temperature
◆ Measurement of transient warming and cooling curve (snapshot voltage/time,thejunction temperature/time and resistance/time curve)
◆ Measurement of dynamic forward voltage/time, the junction temperaturetime and resistance/time curve
◆ Thermostat temperature control：5℃～100℃
◆ Temperature resolution:0.1℃
◆ Temperature instability: not more than 0.4 ℃ / min
◆ Current setting range: 0.1 ~ 2000mA
◆ Current resolution: 0.1mA
◆ Current accuracy: <± 0.5%
◆ Voltage measurement ranges：0-10V
◆ Voltage resolution:0.1mV
◆ Voltage accuracy: <± 0.5%
◆ Measured switching time: less than 50uS.