We know that the LED street lighting projects is a semiconductor diode, the same as a volt-ampere characteristic, and all diodes and semiconductor diode volt-ampere characteristic of a temperature characteristic. Its characteristics when the temperature rises, the volt-ampere characteristic left.
To illustrate how estimates of LED junction temperature. To LED street lighting projects installed inside the radiator, and is a constant current drive power. Should connect to the LED to the two line leads. Put in power before the voltmeter connected to the positive and negative terminals of the output (LED), then connect the power to take advantage of LED heat up before, immediately read the readings of the voltmeter, which is equivalent to the value of the V1, and then at least 1 hour, it has reached thermal equilibrium, and then measured once, the LED voltage across, which is equivalent to V2. These two values subtract the obtained difference. Be 4mV removal, you can come to a junction temperature. In fact, the led high bay lighting is mostly for a lot of series and then parallel, that does not matter when the voltage difference is shared by many series of LED and contribution, so take this voltage difference is divided by the number of LEDs in series is again divided by the 4mV, you can get to its junction temperature. For example, the LED is a 10 string 2 and the first measured voltage is 33V, measured after the second thermal equilibrium voltage of 30V, the voltage difference of 3V. This figure is first divided by the number of LEDs in series (10), and get the 0.3V, divided by 4mV can be 75 degrees. Assumes that the boot before the ambient temperature is 20 degrees, so that when the junction temperature should be 95 degrees.