Signal digitalizing

The ion detection system consists of a high-gain electron multiplier and the signal digitizing system, along with a computer for data acquisition and manipulation. 

In summary, the Fourier transform of a continuous signal digitized in 2A/ + 1 data points returns N real Fourier coefficients, N imaginary Fourier coefficients and the average signal, also called the DC term, i.e. in total 2N + 1 points. The relationship between the scales in both domains is shown in Fig. 40.9. 

Rabiner, 1982] Rabiner, L. R. (1982). Digital techniques for changing the sampling rate of a signal. Digital Audio collected papers from the AES premier conference, pages 79-89. 

Highly sensitive detectors, coupled with the facility to store each absorption signal digitally for each separate analysis time in a microcomputer, have enabled absorbance changes as small as 0.001 to be accurately measured. 

The spectral region of interest is then detected and processed by means of an optical multichannel analyzer (EG G-PARC model 1215, OMA). The OMA detector SIT (silicon intensified target), EG G-PARC model 1254 has been used. It is operated by the detector controller, EG G-PARC, model 1216, which performs the signal digitization as well. The acquired spectra are displayed in real time on a TV display and on the OMA console. The data storage and processing are also performed by that console which has a 28K of 16 bit core memory and a floppy disk for permanent storage. 

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