Digital Resolution

A charged-coupled device (CCD) is a detection system with high sensitivity and a wide dynamic range used to convert the radiation that passes through the optical system of the spectrometer into an electrical charge. The photons that fall on the detector’s photosensitive elements (pixels) are converted into electrons that are amplified and transformed into an electrical signal. This signal, in turn, is converted into a digital number by an analog to digital converter (A/D converter). The digital number of each pixel is generally given in counts.

The number of counts produced by a CCD is restricted by the number of bits from the A/D converter. Taking as an example a 16-bit A/D converter, it is possible to determine that the digital level scale of the detection system is restricted between 0 and 65 535 (216-1). For the case of a 18-bit A/D converter the system is restricted between 0 and 262 143 (218-1). The conclusion is that you’ll get four times mores resolution in the intensity (y-axis of the spectra) of your spectrometer when passing from a system of 16-bit to 18-bit A/D.