Multichannel data acquisition

FIGURE 7.4 Profiles of different masses are built up using a multichannel data acquisition... 

Stored and counted by a multichannel analyzer. This multichannel data acquisition system typically has 20 channels per mass and as the electrical pulses are counted in each channel, a profile of the mass is built up over the 20 channels, corresponding to the spectral peak of Cu. In a multielement run, repeated scans are made over the entire suite of analyte masses, as opposed to just one mass represented in this example. The principles of multielement peak acquisition are shown in Figure 12.3. In this example, signal pulses for two masses are continually collected as the quadrupole is swept across the mass spectrum, shown by sweeps 1-3. After a fixed number of sweeps (determined by the user), the total number of signal pulses in each channel is obtained, resulting in the final spectral peak. ... 

FIG U RE 7.4 Profiles of different masses are built up using a multichannel data acquisition system. (Courtesy of PerkinElmer, Inc., 2003-2012. All rights reserved. With permission.)... 

For the chromatographer who has several (more than four) chromatographs with analog output, multichannel minicomputer-based systems are available from several manufacturers. For the most part, these systems use a minicomputer that is dedicated to the task of data acquisition, data reduction, and reporting of results for a number of chromatographs. Typically, the programs... 

Optical Multichannel Analyzer System (OMA 2). The OMA 2 system consisted of a PARC Model 1215 console, two PARC Model 1254 SIT detectors, two PARC Model 1216 detector controllers, and a PARC Model 1217 flexible disc drive. The SIT detector is controlled by the 1216 detector controller, which provides both power and scanning voltages and processes the signal for transmission to the OMA 2 console. The OMA 2 console performs all necessary control functions, data acquisitions, data processing and storage of spectra. The system can store 250 (500 points) spectral curves when equipped with the Model 1217 flexible disc drive. 

Doppler shift of the photon energy. Data acquisition is performed by a two-parameter multichannel analyzer [1-4],... 

The data acquisition/data handling system consists of a multichannel scalar (MCS) and a computer system. Signal pulses from the detector accumulate into memory channels of the MCS according to their M/Z ratios. Signal pulses from replicate scans are sorted into the appropriate channels and accumulated until the analysis of that sample is complete. A computer program retrieves the totals from the MCS memory and stores the data for later manipulation or display. 

Now, the big difference between multichannel and multiplex techniques arises because a single detector in FT-Raman is collecting all the modulated wavelengths at once. Consider a single data acquisition in an FT experiment, with the interferometer at a fixed position. The detector collects light from... 

The HP 3052A data acquisition system consists of a 9825A calculator with a real time clock, a multichannel scanner, a high speed digital volt meter and a printer/plotter for display purposes. The system software consists of a monitoring program and an analysis program written in HPL. 

Spectra. The energy spectrum is collected from the particles emitted from all depths simultaneously using a silicon surface barrier detector, electronic amplifiers, an analog-to-digital converter and a multichannel analyzer. A reference pulse is fed into the electronics to monitor the stability of the system thus allowing corrections to be made should electronic drift occur during the course of the measurement. Specific systems are described in the references (1 -4,6,7,12-17). By using computer-based data acquisition systems, the depth profile can be displayed at the time of analysis. 

A tunable pulsed laser Raman spectrometer for time resolved Raman studies of radiation-chemical processes is described. This apparatus utilizes the state of art optical multichannel detection and a-nalysis techniques for data acquisition and electron pulse radiolysis for initiating the reactions. By using this technique the resonance Raman spectra of intermediates with absorption spectra in the 248-900 nm region, and mean lifetimes > 30 ns can be examined. This apparatus can be used to time resolve the vibrational spectral o-verlap between transients absorbing in the same region, and to follow their decay kinetics by monitoring the well resolved Raman peaks. For kinetic measurements at millisecond time scale, the Raman technique is preferable over optical absorption method where low frequency noise is quite bothersome. A time resolved Raman study of the pulse radiolytic oxidation of aqueous tetrafluoro-hydroquinone and p-methoxyphenol is briefly discussed. 

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