Option Description
rCL Shows the last 10 measurements recorded. Push to show the
recorded measurements (01—most recent measurement, 10—
oldest measurement). Push to scroll through the measurements.
To select a measurement by number, push to select the number
and then . Push to go out of this option.
SCA Not applicable to the single wavelength models.
3. Push to go back to measurement mode.
Measurement
Basic colorimetry
Colorimetry measures the amount of color in a clear medium, such as
a liquid, to identify the quantity of a particular substance (the analyte) in
the liquid. Typically, the concentration of the analyte is proportional to
the intensity of the color in the clear medium (solution). In most
methods, a darker color indicates a higher analyte concentration.
Absorbance (Abs) at a specific wavelength is typically used to measure
the amount of light absorbed by the solution. Absorbance (Abs) is
calculated as:
Abs = –log T or Abs = –log (I
T
/I
O
)
Where:
T = transmittance
I
T
= intensity of the light transmitted through the sample
I
O
= intensity of the light that enters the sample
Some substances, such as dyes and different metal ions, have
inherent color and can be measured without any additions. In most
cases, a chemical reaction between an indicator and the analyte is
necessary to get a colored product that can be measured.
Once the relationship between the amount of color (measured as
absorbance) and a known concentration of a sample is identified, the
instrument can be used to measure concentrations of unknown
samples. A user-entered calibration curve is used to measure the
sample concentration.
To identify the amount of color in a sample, the instrument measures
the amount of light the solution absorbs. The absorption of light is
dependent on the wavelength of the light and the color of the solution.
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