Specification; Measured Parameters: CFR or Chlorophyll Fluorescence Ratio - fluorescence emission ratio of intensity at 735 nm / 700 nm, or readout or relative chlorophyll content in mg/m2. Measurement Area: 3 mm diameter circle, external diameter of 4 mm. However, the instrument will reliably measure samples that are much smaller than 3 mm. Resolution: Ratio 0.01 or 1 mg/m2. Repeatability: Dependent on signal strength. For samples with low signal strength, averaging of multiple measurements is recommended. For samples with good signal strength, ratio values of +- 0.03 or better, are common. Noise: <+/- 2%. Source: 460 nm blue LED with half bandwidth of 15 nm. Detector: Two solid state, high sensitivity detectors. Band limiting filter sets provided. Dual wavelength detection at the same time. 700 nn to 710 nm, and 730 nm to 740nm. Detection: Modulated light digitally controlled to minimize background detection. Temperature compensation included for light source and detector. Storage Capacity: 2 Gigabytes of non-volatile flash memory. Modes: Single point measurement.Measurement averaging for 2-30 samples. Averaging with 2 sigma outlier removal.Median determination. Sample interface: Fiber-optic probe 4mm in diameter. User Interface: 240 x 320 pixel color touch screen. Output: USB 1.1. Temperature Range: 0-50 Degrees C. Power Source: 2 rechargeable AA batteries. Auto Off Interval: Programmable from 0 to 20 minutes (after no key press or download). Size/Weight: 12 cm x 9 cm x 3 cm./0.6 lbs (275 g). Measuring time: 5 seconds. Components included: Fluorometer, fiberoptic, sample holder, battery charger, 4 AA NiMH rechargeable batteries, USB cable, transport case, and manual.