Data acquisition device

Data Analysis. Part of the benefits of using a microcomputer stem from its ability to act both as a data acquisition device and as a data analysis device. In this study the panelists rated their perceptions by using a pre-coded mark-sense card, shown in Figure 1. The card has 3 positions, allowing the panelists to assign ratings from 0 to 999. 

A portion of the exiting stream of the molten blend is diverted into the Flow Cell , where Nomarsky reflection microscopy is carried out in a thin slit, the bottom plate of which is reflective polished steel and the top is a quartz window. The microscope, the rapid image data acquisition device, and analyzer are capable of producing dispersion data down to sizes of one micrometer. The TSMEE is shown schematically for both the (M-M) and DMM) modes in Fig. 11.31 (119-121). 

The basic setup for 1C is as follows. A pump is used to force the eluent through the system at a fixed rate, such as 1 mL/min. In the FILL mode a small sample loop (typically 10 to 100 pL) is filled with the analytical sample. At the same time, the eluent is pumped through the rest of the system, while by-passing the sample loop. In the INJECT mode a valve is turned so that the eluent sweeps the sample from the filled sample loop into the column. A detector cell of low dead volume is placed in the system just after the column. The detector is connected to a strip-chart recorder or a data-acquisition device so that a chromatogram of the separation (signal vs. time) can be plotted automatically. A conductivity- or UV-visible detector is most often used in ion chromatography. The hardware used in IC is described in more detail in Section 1.4. 

The paper of Diem and Ludl (152) describes a low-cost microcomputer-controlled diode array detector data acquisition device (interface) designed for low-level optical spectroscopies. While these authors are interested in Raman... 

A sheathed thermocouple was inserted axially in the middle of the catalytic bed. Local bed temperatures were recorded continuously by a data acquisition device. A three way solenoid valve (Jefferson model 365) activated by timers was used to generate liquid flowrate variations. Hydrogen was presaturated with AMS. Experiments were performed randomly. Operating conditions used in most of the experiments are given in Table 3... 

Time resolution of changes in the mass spectra can be accomplished in several ways. A TOFMS accessory is available from CVC Products, Inc. (Rochester, NY), which rasters mass spectra across the oscilloscope screen both vertically and horizontally. This device counts a preset number of spectra, n, and then oflFsets the trace both vertically and horizontally. After n more spectra, the trace is again offset. This procedure continues up to the desired number of traces. The device can be used to display 1 16 traces with 1-64 spectra per trace, thus permitting time resolution as low as 0.1 msec. However, the total display time, 16 traces times 64 spectra/trace, is only 0.1 sec. Thus, synchronization of sample loading and/or failure with this data acquisition device is critical. This data acquisition method provides both quantitative and qualitative data about the evolved compounds. However, the mass range which can be displayed effectively is limited to about 100 amu. 

To measure the substances eluting from the column, fractions of mobile phase can be collected and the concentration of the separated components measured externally—for example, in a spectrophotometer or using a pH meter. An automatic fraction-collector which collects a defined volume of column effluent in test tubes is sometimes employed. However, it is more convenient to employ a continuous-detection device at the exit of the column. The detector can be selective (for instance, it detects ultraviolet-absorbing or fluorescent compounds only) or universal (that is, it detects all components). In some cases, two detectors placed in series are used to gain additional information. The detector output is usually displayed on a strip-chart recorder or some other data-acquisition device. For quantitative analysis, an integrator or a minicomputer are useful to automatically measure peak areas. 

Two kinds of data-acquisition approaches can be defined. One is to operate the data-acquisition programming under interrupt control. That is, the computer is operated in a mode where data-acquisition devices are serviced upon demand. The other approach is called program-controlled data acquisition. This approach involves programming the computer to look for service requests from specific devices and to wait for these requests if necessary. The latter approach will be discussed here. 

Boyer and coworkers were the first to develop instrumentation for near-infrared fluorescence immunoassays [117]. WiUiams and coworkers also developed instrumentation for detection of near-infrared fluorescence in sohd-phase immunoassays [118]. The instrument consists of a semiconductor laser coupled with a fiber-optic cable, a silicon photodiode for detection, a sample stage coupled to a motor drive, and a data acquisition device. The instrument could detect 500 pM concentrations of human immunoglobulin G (IgG) on a nitrocellulose matrix. The assay was performed in roughly two hours. The detection limits obtained on this instrument were comparable to that obtainable with ELISA. The assay developed by WiUiams suffers from excessive scatter generated from the membrane, nonspecific binding, and incompatibility with conventional microtiter plate immunoassay formats [140]. Patonay and coworkers developed a NIR fluorescence immunoassay apparatus that overcame many of these limitations. Baars and Patonay have evaluated a novel NIR dye NN382 (Fig. 14.25) for the ultrasensitive detection of peptides with capilary electrophoresis [141]. A solid-phase, NIR fluorescence immunoassay system was... 

Figure 4.85 Basic components of a CE system (1) fused-silica capillary (2) electrolyte vessels with electrodes (3) syringe-to-capillary adaptor (replaced in commercial instruments by pressure or vacuum-driven rinse) (4) sample vial raised to a level necessary for sample introduction by hydrostatic pressure (5) regulated high-voltage power supply (6) detector (7) data acquisition device.

At present, there is no lack of commercially available FIA instruments that can be interfaced with sampling and data acquisition devices or used in combination with other flow methodologies or more recent flow devices. Many of these instruments (fluorimeters, atomic absorption spectrometers, etc.) offer compact setup suited to specific purposes. 

Fig. 19.15 shows the measuring unit. It is made up of a data acquisition device (DAQ, Keithley27(X) with ExceLINX software), a DC power supply (elc, AL 941), a heating resistance (HR), ie, 2 x 2, 5 x 5 cm (Captec Entreprise, France), an insulation material, and a radiator. 

Connectivity and Instrument Control There are ready-to-use libraries for integrating stand-alone instruments, data acquisition devices, motion control and vision product, GPIB and RS232 devices and even PLCs to build a complete measurement and automation solution [5]. 

The most simple data acquisition device, which has been used by generations of automated nutrient analysts, is an analogue multi-pen recorder connected with the photometer voltage output(s). The recorded peaks can be evaluated graphically. Adjusting the delay coils of the manifolds (in multi-channel operation) to identical system times facilitates the sample/peak correlation. This method may be old-fashioned but still is an acceptable setup for testing and developing analytical manifolds. 

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