LM-85 is an Illuminating Engineering Society (IES) approved method for the Electrical and Photometric Measurements of High Power LEDs. The Commission Internationale de L’Eclairage (CIE) has a similar method named TC2-063. LM-85 focuses on the special needs related to getting light measurements for high power LEDs that require heat sinks for their normal operation. White LEDs and single color LEDs are included.
- Single Pulse
- Continuous Pulse
All three methods including DC require pulsed current drive to the LED under test. Typical pulse specifications for each method might be:
|Method||Typical Pulse Width||Needed Rise Time||Delivered Power|
|2||Single Pulse||10-500mS||<100uS||Long duration|
|3||Continuous Pulse||50-200uS||<10uS||Short duration|
These parameters place high-performance demands on the current source. The two key current source specifications are rise time and the continuous available power. Popular source meter instruments sometimes deliver high peak power levels, but only for short durations. They also lack the fast rise times necessary for the DC and Continuous Pulse methods. These limitations mean source-meters are only appropriate with the Single Pulse method, and only when the LED under test is below the source-meter’s continuous power rating.
The SpikeSafe 400 (SS400) can easily perform any LM-85 measurements The SS400 has no power limitations and it has rise times in the 2-6uS range. The chart below compares popular models from Vektrex and Keithley:
|Vendor||Tool||Max Voltage||Max Current||Continuous Power||LM-85 DC||LM-85 Single Pulse||LM-85 Continuous Pulse|
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