What is the recommended value range for chlorophyll fluorescence?
In the raw Fα setting, the values should be at least 1,500 to 2,000 initially. One can have initial values that are lower, but this is not recommended since it will result in the normalised Fα setting having more signal noise due to calculation of the normalised value.
The recommended procedure to achieve raw Fα values of 1,500 or more is to fill the kennel with sample fruit so that each fruit is 'seen' by the small fluorescence detector located in the middle of the FIRM sensor. DO NOT stack fruit because only the top fruit in the stack will be measured.
Take some raw Fα measurements and if the values are too low, replace fruit with ones that are larger or greener so long as they are still representative of the fruit.
If the signal remains lower than 1500 even after this is done that is not a problem so long as one recognises that the normalised Fα values may have more noise. An alternative is to use the raw Fα measurements.