Hanna Instruments HI 83218-01 - Manual (Page 4)

4
PRECISION AND ACCURACY
Precision is how closely repeated measurements agree
with each other. Precision is usually expressed as
standard deviation (SD).
Accuracy is defined as the nearness of a test result to
the true value.
Although good precision suggests good accuracy, precise
results can be inaccurate. The figure explains these
definitions.
For each method, the accuracy is expressed in the
related measurement section.
SPECIFICATIONS
Light Life Life of the instrument
Light Detector Silicon Photocell
Environment 0 to 50°C (32 to 122°F);
max 90% RH non-condensing
Power Supply external 12 Vdc power adapter
built-in rechargeable battery
Dimensions 235 x 200 x 110 mm (9.2 x 7.87 x 4.33")
Weight 0.9 Kg
For specifications related to each method (e.g. range, resolution, etc.) refer to the related measurement
section.
Absorption of light is a typical phenomenon of interaction between electromagnetic radiation and matter.
When a light beam crosses a substance, some of the radiation may be absorbed by atoms, molecules or
crystal lattices.
If pure absorption occurs, the fraction of light absorbed depends both on the optical path length through
the matter and on the physical-chemical characteristics of substance according to the Lambert-Beer Law:
-log I/I
o
=
ε
λ
c d
or
A = ε
λ
c d
PRINCIPLE OF OPERATION