Question: Where in the pulse is the measurement made?
Answer: The 2520 measurement algorithm was designed to prevent problems with the pulse shape causing problems in the reported measurement.
The algorithm described below is used for the laser diode V and I measurements, as well as the photodiode current measurements.
The algorithm starts at the last sample in the pulse (before the pulse fall time begins) and looks back towards the start of the pulse. Using the last A/D sample in the pulse as an “anchor,” it includes samples from the pulse top that are within a certain tolerance (I don’t recall the exact details, but it is something like +/-2-3% or a certain number of A/D counts), calculating a mean (average) for all points within that window.
Product Series: Keithley Optical SourceMeter Instruments