Multi-channel measurement

In another configuration of instmmentation, irradiation of white light onto the electrode surface and detection of reflected light by the use of a multi-channel detector (such as CCD or photo-diode array) through a grating monochromator makes multi-channel measurement possible [21]. 

Multi-channel data provide the best picture of the relationship between measurement points on a machine-train. Data are acquired simultaneously from all measurement points on the machine-train. With this type of data, the analyst can establish the relationship between machine dynamics and vibration profile of the entire machine. 

Fig. 3.7 Pulse-height analysis (PHA) Function of the single-channel analyzer (SCA) and data recording by the multi-channel analyzer (MCA). The output (L) of the SCA yields a 5 V squareshaped pulse, a so-called TTL pulse for each y-pulse matching the voltage selection window. The SCA is set to select the Mossbauer pulses for the subsequent measurement...

Fig. 3.1. Schematic diagram of a TCSPC setup. Using a fast timing device (e.g., time-to-amplitude-converter) the time is measured between the excitation pulse and the detection of a photon. By repeating this procedure many times a decay curve is measured. TAC time to amplitude convertor, MCA multi channel analyzer, PC personal computer. 

Immunosensors have been developed commercially mostly for medical purposes but would appear to have considerable potential for food analysis. The Pharmacia company has developed an optical biosensor, which is a fully automated continuous-flow system which exploits the phenomenon of surface plasmon resonance (SPR) to detect and measure biomolecular interactions. The technique has been validated for determination of folic acid and biotin in fortified foods (Indyk, 2000 Bostrom and Lindeberg, 2000), and more recently for vitamin Bi2. This type of technique has great potential for application to a wide range of food additives but its advance will be linked to the availability of specific antibodies or other receptors for the various additives. It should be possible to analyse a whole range of additives by multi-channel continuous flow systems with further miniaturisation. 

The hematite with adsorbed Co-57 or Sb-119 along with the solution was subjected to emission Mossbauer measurement at 24 1°C with the experimental setup shown in Figure 2. The absorber, Fe-57-enriched potassium ferrocyanide (0.5 mg Fe-57/cm2) or barium stannate (0.9 mg Sn-119/cm2), was driven by a Hanger 700-series Mossbauer spectrometer connected to a Tracor-Northern TN-7200 multi-channel analyzer. The Mosssbauer gamma-rays of Co-57 and Sb-119 were detected respectively with a Kr(+3% carbon dioxide)-filled proportional counter and with a 2 mm-thick Nal(Tl) scintillation counter through 65 pm-thick Pd critical absorber for Sn K X-rays. The integral errors in the relative velocity were estimated to be of the order of 0.05 mm/s by repeated calibration measurements using standard absorbers. 

Laboratory furnaces. Several types of furnaces are used in the laboratory these are often available as commercial rigs, generally equipped with more or less sophisticated temperature measurement and control devices. As an alternative, a lab-made or commercial furnace and its temperature measuring devices may be connected to a multi-channel data acquisition/actuator/switch unit, to be programmed by a personal computer, in order to plan and carry out thermal treatments, to collect and retrieve measured thermal data, etc. 

Table 1.2 gives some of the reasons for the LGC setting up its automation team. The primary motivation was economic. LGC was often subject to constraints on staffing in parallel with large increases in analytical commitments. The introduction of cost-effective analyses, using mechanical or automatic instruments, reduces staff involvement and allows well qualified people to be released for the development of new analytical requirements. The analysis of beer samples by multi-channel continuous flow analyser [S, 6, 7] and the introduction of a mechanical solvent extraction and identification system to analyse and measure levels of quinizarin in gas oil, both for duty purposes, were prime examples [8], Both systems involved commercially available components and/or instruments integrated with modules designed and built in-house. 

The electrochemical procedure was run with the PalmSens electrochemical analysis system, with the software package. All measurements were carried out using the multi-channel system with a Mux acquisition data that allowed to work with eight electrodes in quick succession. 

We have used a Reticon photodiode array and an Optical Multi-channel Analyzer to measure optical density changes Induced in photovisual materials using this technique. The Reticon is a device which incorporates a linear high density monolithic array of silicon photodiodes with integrated scanning circuits for serial readout. The array consists of 128... 

Non-dispersive systems are very compact, and potentially less expensive than dispersive spectrometers. For this reason they may be used for multi-channel instruments, measuring upto six elements almost simultaneously.39,40 Although... 

Direct measurement of short-lived reactive intermediates by time-resolved spectroscopic methods is very important for understanding the detailed mechanisms of radiation effects. Very recently a new ion beam pulse radiolysis system using optical multi-channel detection has been developed. Although the use of ion beam pulse radiolysis for studying the radiation effects of ion beams on polymers was first reported by us [3, 30], the new system is highly modified for investigating ion beam reactions. Electron beam pulse radiolysis was also carried out complementarily. 

As discussed above, a convenient way of measuring the detonation velocity is to convert the light signal using a fast photodiode that has a rising time of about 10 ns into an electric signal that may be recorded by either a fast oscilloscope (Fig. 7.13) or a multi-channel analyzer (Fig. 7.14). 

Analysis. The analytical system used for gamma-ray measurements consisted of a lithium drifted germanium (GeLi) crystal detector, a 4096 multi-channel analyzer, a PDP 11 computer, and a cassette magnetic tape storage. The germanium detector crystal has a volume of 55 cm with FWHM resolution of 2.3 keV at 1.33 MeV. The computer was used to analyze the gamma ray spectra, to identify the radio isotopes, and to calculate the concentration (Table III). 

The classical time measuring system, the combination of a Time-to-Amplitude Converter (TAG) and a Multi-Channel-Analyser (MCA) has a much longer deadtime of the order of 20 psec. 

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