Data acquisition, digital

Because of the medium or relatively large sample quantities used and the instrumental sensitivity, isoperibolic calorimetry is a useful tool in determining the onset temperature of an exotherm. In fact, in its simplest construction, this is really the only measurement. Digital data acquisition does allow computer analysis of the peak or area under the curve, which indicates the order of magnitude of the exotherm. Generally, the detected onset temperatures are similar to those found in the ARC (see later in Section 2.3.23) and are significantly lower than in the DSC (Section 2.3.1.1) [79]. 

Of course if the required information is gathered from one particle at a time, it becomes necessary to make observations on a very large number of particles in order to properly characterize the assembly. It is therefore fortunate that the scanning mode of operation of the STEM instrument makes it ideally suited to the automated collection of data. Also the computer-based digital data acquisition and analysis systems are now reaching the state of sophistication which makes it possible to contemplate the necessary handling of large numbers of one- or two-dimensional arrays of data. 

R. N. Goldberg, R. L. Nuttall, E. J. Prosen, A. P. Brunetti. Digital Data Acquisition and Computer Computation Applied to Calorimetric Experiments. Nat. Bur. Stand. Report 1971, 10437. 

Hites, R.A. Biemann, K. A Computer-Compatible Digital Data Acquisition System for Fast-Scanning, Single-Focusing Mass Spectrometers. Anal. Chem. 1967, 39, 965-970. 

More elaborate entries, such as "23CD5", ere occasionally necessary this one denotes the use of a three-electrode cell with an agar bridge, deaeration by both hydrogen and sulfite, and digital data-acquisition. When insufficient information was given to permit completing any part of this three-character code, a dash always appears in the appropriate position, as in the entry "0-0". This permits easy differentiation between, for example, "—0" and "0--". 

A test system, controlled by personal computer (PC), was developed to evaluate the performance of the sensors. A schematic of this system is shown in Figure 3. The signals from the sensors were amplified by a multi-channel electrometer and acquired by a 16 bit analog to digital data acquisition board at a resolution of 0.0145 mV/bit. The test fixture provided the electrical and fluid interface to the sensor substrate. It contained channels which directed the sample, reference and calibrator solutions over the sensors. These channels combined down stream of the sensors to form the liquid junction as shown in Figure 1. Contact probes were used to make electrical connection to the substrate. Fluids were drawn through the test fixture by a peristaltic pump driven by a stepper motor and flow of the different fluids was controlled by the pinch valves. 

In this article we try to give a survey on fundamental principles of data acquisition. As it is certainly beyond the scope of this text to present a thorough representation of the technical details and tricks involved in data acquisition we intend to show the capabilities and limits of digital data acquisition and to provide some explanation of the technical terms involved. In order to get a closer view of this topic the interested reader should also take a look into textbooks (ref. 1-5). 

Cl. Chilcote, D. D., and Mrochek, J. E., Use of automatic digital data acquisition and on-line computer analysis in high-resolution liquid chromatography. Clin. Chem. 17, 751-756 (1971). 

Simple digital data acquisition. For more advanced students, PC-based or PDA-based data acquisition and analysis of data are possible. This are skills that students in technical fields need to learn. 

The following short sections deal with how the FT NMR experiment is performed in terms of setting the correct parameters. They dovetail into many of the sections in Chapter VI. Aside from the specific references listed in each section and the general references in Appendix A, there are other good reviews of the how and why of FT NMR. For example, there is a compact elementary treatment by Van Hecke (1977), which can be read quickly to get an idea of the field. A different kind of a reference we cite here is an in-depth article specifically on digital data acquisition and processing in FT NMR by Lindon and Ferrige (1980). 

Schwlng at al. [7] developed a potentlometric-voltammetrlc system with digital data acquisition and treatment for the kinetic determination of mixtures of metal Ions based on ligand-exchange reactions. The resulte obtained from potentlometrlc measurements are more precise than those found with ampero-metrlc measurements (the typical relative errors are 5% and 5-10, respectively). 

The improvemcnl in S/N ihai is realized by signal averaging is exploited in many areas of science NMR spectroscopy and Fourier transform infrared speciro scopy arc but two of the most prominent examples in chemical inslrumenlaiion. We consider signal averaging and other aspects of digital data acquisition in more detail in the chapters on those lopics. 

The transducer in a lOF mass spectrometer is usually an electron multiplier whose output is displayed on the vertical deflection plates of an oscilloscope and I he horizontal sweep is synchronized with the acceler ator pulses an essentially instantaneous display of the mass spectrum appears on the oscilloscope screen. Be cause typical flight times are in the micro.second range digital data acquisition requires extremely fast elec... 

There has been a tremendous growth in the study of human movement in the past 2 decades because of the low cost of digital data acquisition systems that make possible the storage and analysis of massive amounts of data that are required to accurately characterize complex motion. This growing interest in the study of human movement is coming from five predominate groups ... 

A set of fundamental criteria estabUsh-ing the limits for digital data acquisition. For example, a minimum of two points taken in a specified time are required to define a wave and its frequency. The Nyquist frequency is the maximum frequency represented accurately in a spectrum and is set by the dwell time in the digital acquisition. 

Standard Guide for Digital Data Acquisition in Wear and Friction Measurements... 

AES measurements were carried out in a differentiated mode with a 2 eV modulation amplitude, at either 3 or 0.5 keV of primary electron energy, and 0.5 pA sample current, using a Perkin Elmer (PHI) 10-155 cylindrical mirror analyzer (CMA). The analysis was conducted at a low beam current to minimize electron beam damage. Spectra were acquired using a digital data acquisition system, and smoothed one time using a 11 point averaging technique.. 

The specimen temperature may be measured by means of a thermocouple attached to the specimen, or it may be derived from the electrical resistance (this requiring calibration in separate steady-state experiments), or it may be measured by automatic optical methods. The potential differences produced by the transducers used in the measurements are recorded either by using an oscillograph, or by photographing oscilloscope traces, or by using high-speed digital data-acquisition systems. 

Vibrational spectroscopies (mid-IR, near-IR, Raman) play an important role in polymer/additive analysis. Optical advances as well as spectacular advances in computing technology and data processing algorithms have greatly impacted vibrational spectroscopy over the past 25 years (cfr Table 1.5). Rapid digital data acquisition is required for FTIR, FT-Raman or CCD-Raman spectroscopy. The raw data obtained from these instruments must always be manipulated before a recognisable spectrum can be displayed. 

Until recently all data other than temperature and pressure on emulsion polymerization systems were obtained almost exclusively through manual, off-line analysis of monomer conversion, emulsifier concentration, particle size, molecular weight, etc. Recent interest in closed-loop control of both batch and continuous emulsion polymerizations has resulted in the development of a number of sensors capable of continuously monitoring the states of an emulsion polymerization system. These sensors provide a continuous (or frequently-updated discrete) electronic signal which is compatible with state-of-the-art digital data acquisition and control systems. 

Methods have recently been developed for the monitoring of monomer conversion and emulsion surface tension (free surfactant conversion and emulsion surface tension (free surfactant concentration). These methods are continuous, on-line, and compatible with digital data acquisition and control systems. A number of methods have been proposed for the measurement of particle size distribution. Of these, a few seem to offer promise for... 

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