SpotOn 35650, Product Manual, Page: 3 / 36

INSTRUCTIONS IN ENGLISH
| QUANTUM PAR LIGHT METER
1
UNDERSTANDING PAR LIGHT:
This meter is designed for measuring PAR light indoors and outdoors regardless of light source
type. It works well for greenhouse, field, and R&D applications requiring reliable plant growth
light readings.
The chemical reaction of photosynthesis requires light. Unlike energy based light measurements,
the quantum (quantity) of photons is measured since it can be directly tied to the number of
these chemical reactions that can take place. The measure of all available light between the
wavelength (color) range of 400 to 700 nanometers(nm) has been accepted as the best measure
of light available for photosynthesis. This is defined as quantum Photosynthetic Active Radiation
(PAR) in units of µmol m-2 s-1. This is referred to as PAR light, PPFD, PPF, and Quantum light
interchangeably and is the total quantity of photons in µmoles over the light spectrum from
400 to 700 nm hitting a one-meter square area every second. One micromole is equal to
602,214,085,700,000,000 photons of light! This is not the same as foot candle or lux measurements
as shown in Fig. 1.
The meter can also determine the total number of photons incident on one square meter over
a 24-hour period. This is defined as the Daily Light Integral (DLI) and is displayed in moles per
square meter per day. The typical range for DLI is 3 to 26 moles m-2 day-1. This is useful for
understanding the average amount of light your crop sees in a day. One mole is equal to one
million micromoles.
Foot Candle/Lux meters measure
(Human Eye Response)
Fig. 1 – PAR vs. Human Eye Spectrum
PAR meters measure
(Plant Response)
Wavelength (nm) Wavelength (nm)
WARNING:
Battery can explode or leak and cause burns if installed backwards, disassembled,
charged, or exposed to water, fire or high temperature. CR2032 Battery CALIFORNIA
ONLY: Perchlorate Material – special handling may apply. See www.dtsc.ca.gov/
hazardouswaste/perchlorate.
SpotOn® Quantum PAR Light Meter Item #35650