PASCO SE-7183 Spectrometer - Manual (Page 10)

8
A BOUT THE MEASUREMENTS
About the measurements
Intensity
This is the straight measurement made by the spectrometer as a percentage of
the maximum possible measurement. You can use this measurement with first
recording a reference scan or dark scan.
Minus Dark
SPARK calculates Minus Dark by subtracting the dark scan from the Intensity
measurement.
You must save a dark scan before using this measurement (see “Editing the
spectrometer properties” above).
Absorbance
SPARK uses this equation to evaluate each pixel on the detector and produce the
absorbance spectrum:
Where:
S
λ
= Sample intensity at wavelength λ
D
λ
= Dark intensity at wavelength λ
R
λ
= Reference intensity at wavelength λ
Absorbance is not a valid quantity if either (S
λ
- D
λ
) or (R
λ
- D
λ
) is less than or
equal to zero. This condition may occur if the test solution or the reference
solution is very dark.
You must save a dark scan and a reference scan (typically with a cuvette
containing a 0% solution) before using this measurement (see “Editing the
spectrometer properties” above).
Transmission
SPARK calculates the transmission of a solution using this equation:
You must save a dark scan and a reference scan (with a cuvette containing a 0%
solution) before using this measurement (see “Editing the spectrometer
properties” above).
A

log
10
S

D

–
R

D

–
-------------------
 
 
– =
%T

log
10
S

D

–
R

D

–
-------------------
 
 
– 100%  =