Different types of instruments

In this second class of spectrometers, known for their excellent spectral resolution, the X-ray radiation emitted by the sample passes through a collimator made of long 

For construction reasons, d can vary from 5 to about 80°. A greater value of d leads to greater wavelengths, however the resolution of the instrument is linked to 

Low energy transitions for elements up to phosphorus (Z = 15), require operating conditions in a vacuum. The resolution can be as low as a few electron-volts. There exists models of this type which are adapted for scanning electron microscopes. 

These are robust instruments often installed on site for the continuous monitoring of industrial production sequence. In most of these cases, the object is to measure a single element present in a fabrication process, from a particular and typical transition, provided that line can be isolated from the rest of the spectrum. 

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Frequently an analyst must select, from several instruments of different design, the one instrument best suited for a particular analysis. In this section we examine some of the different types of instruments used for molecular absorption spectroscopy, emphasizing their advantages and limitations. Methods of sample introduction are also covered in this section. 

Each of these experimental designs also uses a different type of instrument. To aid in understanding how they control and measure current and potential, these instruments are described as if they were operated manually. To do so the analyst... 

The IDL is dependent on various factors such as sensitivity of the detector for the analyte of interest and electronic and detector (instrumental) noise of various origins, e.g., thermal noise, shot noise, flicker (1 //) noise, environmenfal noise, efc. Several books and articles have been published on fhe different types of instrumental noise, e.g., Skoog and Leary s Principles of Instrumental Analysis . ... 

When the work is carried out on a compaction simulator, it is possible to subject the formulation to high-speed tableting cycles in order to evaluate strain forces in the compacts. This work can be of utmost importance, since it appears that strain rates can exert strong influences on a variety of tablet properties [64]. The information gathered in this way can be used to aid in the transfer of the manufacturing process among different types of instrumentation, and to aid ir the technology transfer process. 

TABLE 6.3. Types of Ions Formed in Different Types of Instruments... 

Different types of instrumentation have been developed to introduce Hquid samples into the MS. Since Fenn has shown that molecular ions can be formed from liquids sprayed at atmospheric pressure in high electric fields, electrospray ionization (ESI) MS has gained increasing popularity for the analysis of biological samples [56]. In an electrospray inlet, the liquid sample is usually emitted as a spray from a capillary at a high potential compared to the mass analyzer into the electric field in front of the mass analyzer (Fig. 8). 

Autoscaling is often necessary in cases when the X-variables come from different types of instruments (e.g. FTIR, GC, ISEs), or when the units of measurement are not the same for all of the variables (e.g. ppm, %, °C, pH units). In such cases, if autoscaling is not done, then those variables with the largest absolute range will tend to dominate in the modeling process, and those with the lowest absolute range will tend to be ignored. 

For instance, the manganese determination by molecular absorption spectro(photo)metry can be made using different types of instruments which have various technical performances. Some results are shown (Fig. 4) for manganese concentration measurements with a DR 2000-wide bandwidth 8 nm (series 1) a Hewlett Packard 8452 A, bandwidth 2 nm (series 2) and a Spe-cord M 40-narrow bandwidth 1 nm (series 3). 

Before any evaluation, the essential characteristics required of the instrument must be defined. These will include accuracy, precision, specificity, and speed, and methods for measuring these may need to be devised. To these objective criteria must be added a range of subjective factors, including ease of use, reliability, safety, and ease of maintenance. Finally, all these factors must be related to the price of the instrument. In Britain a schedule for testing automated equipment has been prepared (B17) which with minor modifications can be applied to many different types of instrument. 

Compaction simulators can be fitted with instrumented dies to measure the stress that the powder exerts on the die wall during the compaction and ejection cycle. Different types of instrumented dies have been constructed with single or multiple transducers to measure the die wall stress. The literature reports some examples of different config-urations of the pressure transducers within the instrumented die (13), as shown in Figure 7. 

In order to generate reliable quantitative results by Py-GC or Py-GC/MS, an important requirement is the repeatability of the analysis. Any variation of the parameters of the Py-GC/MS analysis may influence the outcome. For this reason, the quantitation using Py-GC/MS is more difficult than that in typical chromatography. The variability is a result of the fact that certain steps in the pyrolytic process may not be perfectly reproducible. Reproducibility is mainly affected when the same sample is analyzed with different types of instruments. However, for the same instrument and the same amount of sample, the reproducibility can be very good. As an example, two pyrograms of 0.4 mg sample of... 

Many different types of instruments have been available during time. In Denmark the first... 

Instruments for online measurement of dry and wet systems is also available. Due to the diversity of measurement techniques and the varying definitions of characteristic length, different types of instruments most likely will give different PSDs, for nonspherical particles. Therefore, it should be understood that there is no absolute standard for PSD measurement. 

Hundreds of HRQOL instruments are available. ° Table 2-1 gives a taxonomy of the different types of instruments. A primary distinction among HRQOL instruments is whether they are generic or specific. 

There are several different types of instrument covered under the term DSC, which have evolved from differential thermal analysis (DTA) and measure the temperature difference between sample and reference pans located in the same furnace. This is then converted to heat flow using a calibration factor. A detailed analysis of DSC requires consideration of the various sources of heat loss, and these are generally captured in the calibration routine for the instrument. Absolute temperature calibration is achieved through the use of pure indium (156.6 °C) and tin (231.9 °C) melting-point standards. A comprehensive analysis of the theory of DSC contrasted with DTA may be found in several reference works (Richardson, 1989, Gallagher, 1997). 

No single instrument at present has all the desired characteristics. Accordingly, different types of instruments must be used depending upon the nature of the radiation hazard. The characteristics of some of the more commonly used detectors are summarized below. 

The term differential scanning calorimetry has become a source of confusion in thermal analysis. This confusion is understandable because at the present time there are several entirely different types of instruments that use the same name. These instruments are based on different designs, which are illustrated schematically in Figure 5.36 (157). In DTA. the temperature difference between the sample and reference materials is detected, Ts — Tx [a, 6, and c). In power-compensated DSC (/), the sample and reference materials are maintained isothermally by use of individual heaters. The parameter recorded is the difference in power inputs to the heaters, d /SQ /dt or dH/dt. If the sample is surrounded by a thermopile such as in the Tian-Calvet calorimeter, heat flux can be measured directly (e). The thermopiles surrounding the sample and reference material are connected in opposition (Calvet calorimeter). A simpler system, also the heat-flux type, is to measure the heat flux between the sample and reference materials (d). Hence, dqjdi is measured by having all the hot junctions in contact with the sample and all the cold junctions in contact with the reference material. Thus, there are at least three possible DSC systems, (d), (c), and (/), and three derived from DTA (a), [b), and (c), the last one also being found in DSC. Mackenzie (157) has stated that the Boersma system of DTA (c) should perhaps also be called a DSC system. 

In addition to search systems, artiheial intelligence-based computer programs seek to determine the structure or substructure from spectral proliles. Some of these programs use data from different types of instruments (nuclear magnetic resonance, mtiss. and IR spectrometers, etc.) to determine structures. ... 

Hydrophilic colloids do not, in general, obey Poiseuille s law, for their viscosity depends on the shearing force to which the solution is subjected. In general, the viscosity of such solutions decreases as the rate of shear is increased, as the long polymer molecules tend to orientate with their long axes more nearly parallel to the streamlines of flow and thereby offer less resistance to flow (7), Consequently, results obtained with different types of instruments, or with the same instrument but different shearing forces, are not directly comparable (S). 

There are different types of instruments that can be attached to the El source for MS analysis. The most commonly used technique consists of the analysis of a gaseous sample obtained from the gas chromatograph. However, other introduction systems, such as reservoir inlets and direct insertion probes, are also frequently used. 

A FMEDA is sometimes done by the instrument manufacturer but typically done by third party experts. Often a product manufacturer does the work as part of an IEC61508 functional safety certification effort. Many different types of instruments have had this analysis done. A listing of... 

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