Light Box Design
The sample chamber in the middle holds a cuvette. Light from a LED passes through the sample to the detector. Note the slots for inserting light filters. The design allows for the light source and detector to be be placed at any of the four sides. For absorbance, the light source and detector are on opposite sides. For fluorescence or turbidity, the detector is placed at right angles to the light source.
A graph showing how the LED output varies with circuit resistance is shown here.
Terms and Definitions.
Cuvette - A clear rectangular vessel for holding the sample. It is 1.0 cm across internally, so the light passes through 1 cm of liquid.
LED - Light emitting diode. The wavelength and intensity can be varied, depending on the intended use.
Detector - The level of light can be measured using a photoresistor, a light-to-voltage converter or a light-to-frequency converter.
Filter - Thin colored plastic strip. A filter can be placed between the light source and the sample to modulate the color or intensity of light.