Milestone DMA-80 evo - Page 127

Milestone Srl MA213-003 – DMA-80 EVO – User Manual
125
The double beam function is an option available for DMA-80 EVO units with configuration Dual cell and
Tri cell. A dedicated detector, also called “reference”, is installed directly in front of the lamp and in perfect
line with the smallest cell (cell 0 in case of tri cell, cell 1 in case of dual cell) for the continue monitoring of
its complete intensity.
The double beam function guarantees a better signal to noise ratio, a lower quantification limit and a
superior precision.
It works like follow: The software takes account of the maximum and minimum (lamp off) intensity of the
light detected by the detectors before each analysis
- Maximum intensity of the light =100%
- Minimum intensity (lamp off) = 0%
Therefore:
- Maximum intensity (100%) - Minimum intensity (0%) = 100% of light
The electrical amplification (GAIN value) does not matter at this point, because it is a relative
measurement.
The corrected signal is:
%detector Hg / %reference * 100%
Where:
- % detector is the % of light on the measuring detector (back to smaller cell). Blue line
- % reference is the % of light on the reference detector (double beam detector). Viole line
- Corrected signal is the signal used for final peak detection in order to have a more stable baseline.
Yellow line
Example of baseline correction with variation of the % light
In this page you can also check the stability of detector signal and signal noise.