Instruments magnetic measurements

A turbine flowmeter consists of a straight flow tube containing a turbine which is free to rotate on a shaft supported by one or more bearings and located on the centerline of the tube. Means are provided for magnetic detection of the rotational speed, which is proportional to the volumetric flow rate. Its use is generally restric ted to clean, noncorrosive fluids. Additional information on construction, operation, range, and accuracy can be obtained from Holzbock (Instruments for Measurement and Control, 2d ed., Reinhold, New York, 1962, pp. 155-162). For performance characteristics of these meters with liquids, see Shafer,y. Basic Eng., 84,471-485 (December 1962) or May, Chem. Eng., 78(5), 105-108 (1971) and for the effect of density and Reynolds number when used in gas flowmetering, see Lee and Evans, y. Basic Eng., 82, 1043-1057 (December 1965). 

The direction of rotation depends on the direction of the current in the coil, and thus the instrument is only suitable for D.C. It is, however, possible to incorporate a full-wave rectifier arranged as shown in Figure 17.11 in order to allow the instrument to measure A.C. quantities. The quantity measured is the RMS value only if the waveform of the current is truly sinusoidal. In other cases, a considerable error may result. In principle, the scale is linear but, if required, it can be made non-linear by suitably shaping the poles of the permanent magnet. The instrument reading is affected by the performance of the rectifier, which is a non-linear device, and this results in the scale also being non-linear. The error when measuring D.C. quantities can be as low as 0.1 per cent of full-scale deflection and instruments are available for currents between microamperes and up to 600 A. 

In mass spectroscopy, sample molecules are ionized and the different masses of the ions formed are selected by use of an electric or magnetic field. In its simplest form, a mass spectrometer is an instrument that measures the mass-to-electric charge ratios of ions formed when a sample is ionized. If some of the sample molecules are singly ionized and reach the ion detector without fragmenting, then the mass-to-electric charge ratio of the ions gives a direct measurement of the weight of the molecule (de Hoffmann and Stroobant 2001). 

If one wishes to obtain a fluorine NMR spectrum, one must of course first have access to a spectrometer with a probe that will allow observation of fluorine nuclei. Fortunately, most modern high field NMR spectrometers that are available in industrial and academic research laboratories today have this capability. Probably the most common NMR spectrometers in use today for taking routine NMR spectra are 300 MHz instruments, which measure proton spectra at 300 MHz, carbon spectra at 75.5 MHz and fluorine spectra at 282 MHz. Before obtaining and attempting to interpret fluorine NMR spectra, it would be advisable to become familiar with some of the fundamental concepts related to fluorine chemical shifts and spin-spin coupling constants that are presented in this book. There is also a very nice introduction to fluorine NMR by W. S. and M. L. Brey in the Encyclopedia of Nuclear Magnetic Resonance.1... 

An instrument that measures the isotopic mass ratio of a gas by bombarding the sample in an electron beam, such that the molecular ions generated can be deflected in their trajectories through a magnetic field in accordance to their charge/mass ratios. These devices are extremely accurate and reliable, and many stable isotope experiments can be analyzed by converting the isotopi-caUy substituted metabolite into carbon dioxide, water, or molecular nitrogen prior to I RMS measurements. 

Magnetic measurements require access to appropriate instrumentation, onsite or through collaboration. Large research centers such as the U.S. National... 

Thermal analysis is capable of providing accurate information on the phase transition temperatures, degradation temperatures, heat capacity, and enthalpy of transition of polymers using comparatively simple DTA, DSC, and TG instruments. The measurement time is short compared with other techniques, such as viscoelastic measurement and nuclear magnetic resonance spectroscopy. Moreover, any kind of material, e.g., powders, flakes, films, fibers, and liquids, may be used. The required amount of sample is small, normally in the range of several milligrams. 

Instrumentation Isotopic measurements were carried out with a DP-102 magnetic sector mass spectrometer (DuPont Instrxments) operated in the electron-impact ionization mode. Because the chelate was thermally unstable and decomposed on a GO column, direct probe introduction was used a capillary tube containing the chelate was placed in the sample cup at the end of the probe. The temperature of the ion-source chamber was set at HO C and the probe heater was turned off. 

NMR spectrometer (Section 14.1 A) An analytical instrument that measures the absorption of RF radiation by certain atomic nuclei when placed in a strong magnetic field. 

Wave Astronomy Satellite (SWAS) show the abundance to be less than 0.1% that of CO. At this level, it does not interfere with organic synthesis. With elemental evolution, an increase of the 0/C ratio is expected. If this is not readily incorporated into the refractory solid phase, production of organic species in the interstellar molecular clouds could well be reduced. CO is an abundant molecule in strongly red shifted quasars (Downes and Solomon, 2003) (z = 2.6-6.4). Thus, it would be expected that its reaction products also are present, but harder to observe. SWAS is instrumented to measure O2 abundances and has not observed any. (O2, although lacking an electric dipole moment, has magnetic dipole transitions.) Note that it has probably not been observed in dense molecular clouds. 

AMS does not determine the absolute concentration of isotopes rather an isotope ratio of a rare isotope to an abundant stable isotope of the same element is measured. There is no commercially available AMS instrument that measures all isotopes, such that most instruments are built to detect one or two elements only. Highly specialized, complex, and time-consuming sample preparation is often required prior to AMS analysis. AMS instruments for various radioisotope analyses have been reviewed in a recent publication [14], Here we would only discuss AMS instrument for 14C analysis, the most important radioisotope for biomedical applications. For 14C measurement, an AMS instrument usually consists of an ion source to generate negative ions, a low magnetic field for initial ion separation, a high-voltage... 

IR spectra were recorded with a Nicolet 2DXFT-IR spectrophotometer as KBr pellets in the 4000-500 cm" region. The UV-visible and reflectance were run on a VSU-2G spectrometer using MgO as the reference for the reflectance spectra. Molar conductances were measured at room temperature on a Radelkis KFT conductivity meter. Metal ions were determined on a Pye-Unicam atomic absorption spectrophotometer. Elemental analyses were done by combustion with a Carlo Erba instrument CHNS Elemental Analyser Model 1106. Magnetic measurements were carried out at room temperature with a Faraday-type magnetometer. 

On-line moisture monitors, which are based on infra-red absorption, nuclear magnetic resonance, capacitance and microwave attenuation are used in numerous process industries. The applicability of these techniques to the coal preparation industry has been reviewed (13,14). The CONAC and "Elemental Analyzer" units use a microwave attenuation method for the moisture measurement. This information is used to correct the PNAA hydrogen assay data in order to calculate the hydrogen content of the coal. Kay-Ray, Inc., (Arlington Heights, Illinois) has developed an instrument that measures the moisture content of a coke stream and uses a combination of microwave and gamma ray attenuation measurements. 

Magnetometer Instrument that measures magnetic intensities. 

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