plant chlorophyll meter, leaf sensor
atLEAF CHL PLUS and atLEAF CHL BLUE accuracy & repeatability

Accuracy among devices

Max error -0.5 ... +0.5
Mean error 0.2
Std Dev on error 0.2

How it is evaluated

All devices are calibrated and, using two different filters, measured at reference values 31.8 and 65.3.
The accuracy for device i is evaluated as :

 Errori = ( ( M1i - 31.8 ) + ( M2i - 65.3)) / 2

   M1i is the measure value of device i with filter at 31.8 and
   M2i is the measure value of device i with filter at 65.3

Maximum error
N ... number of produced devices
maximum positive error = for (i=0 to N) maximum(Errori)
maximum negative error = for (i=0 to N) minimum(Errori)

Mean error
mean error = (abs(Error0) + abs(Error1) + .. + abs(ErrorN)) / N

Std Dev on error
Std Dev on error = sqrt ( (sum (Errori - mean error)2) /N )


Tested on 303 measures with an optical filter.

Min value: 36.1
Max value: 36.2
Std Dev: 0.046
CV: 0.13%

View the test measures.

How it is evaluated

The measures are performed remotely with atLEAFSoft PRO software, with the atLEAF CHL PRO connected through a USB port. For this test the period among measures is set to 2s, while the available software has a minimum selectable period of 10s.
The sample used for evaluating the instrument repeatability is an optical filter.
View the video of the test.

Repeatability on a green plant

A similar test was also performed on a living green plant (Pothos, Epipremnum aureum). The leaf was not moved during the test and the measures were made with a period of 2s (while available atLEAFSoft version allows remote acquisitions with a minimum period of 10s). After a series of 100 measures, the reported series of 200 measures was performed. The results were:

Min value: 50.1
Max value: 50.3
Mean value: 50.2
Std Dev: 0.054
CV: 0.11%

View the test measures.