Last Fall our students used the multispeQ and collected SPAD values.
So if I want to compare SPAD from Fall 2014 to SPAD III protocol this year which value do I use: PQ SPAD or PQ SPAD 1 or PQ SPAD 2 or PQ SPAD 3, to compare to Fall 2014?
You should use PQ SPAD. In the SPAD III measurement we are measuring SPAD at three different light intensities (PQ SPAD 1, PQ SPAD 2, PQ SPAD 3) to account for differences in leaf thickness. The macro then decides which of these SPAD measurements are best and uses those SPADs. So the PQ SPAD number is the average of the best SPAD measurements, which may be all three SPAD's, or maybe it is the average of PQ SPAD 1 and 2, or PQ SPAD 2 and 3, depending on how absorption is affected by the thickness of the leaf.
Thanks for the reply. Can wait to make comparisons.
So which specific light intensities are being done for each PQ SPAD1, PQ SPAD 2 and PQ SPAD 3?
The SPAD measurement uses light intensities of 125, 750, and 3000 for the 650 LED and 2465, 3000, and 4000 for the 940 LED for PQ SPAD 1, 2, and 3, respectively.