Detector measurements

In the case, where all 3 phases are present, the detector measurements reveal the amounts of tracers in each phase and the position of the boundaries between the phases The cross section area of each phase is calculated fi-om the latter. From this the tracer concentrations and hence the volume flows of the 3 phases are calculated. 

Measurements have been made in a static laboratory set-up. A simulation model for generating supplementary data has been developed and verified. A statistical data treatment method has been applied to estimate tracer concentration from detector measurements. Accuracy in parameter estimation in the range of 5-10% has been obtained. 

Ion-exchange columns can be substituted into the general HPLC instrument shown in Eigure 12.26. The most common detector measures the conductivity of the mobile phase as it elutes from the column. The high concentration of electrolyte in the mobile phase is a problem, however, because the mobile-phase ions dominate the conductivity, for example, if a dilute solution of HCl is used as the mobile phase, the presence of large concentrations of H3O+ and Ck produces a background conductivity that may prevent the detection of analytes eluting from the column. 

Area Detectors. A two-dimensional or area detector attached to a powder diffractometer can gready decrease data collection time. Many diffraction appHcations require so much time with a conventional detector that they are only feasible if an area detector is attached to the iastmment. The Siemens General Area Detector Diffraction System (GADDS) uses a multiwire area detector (Fig. 17). This detector measures an x- and ajy-position for each x-ray photon detected. The appHcations foUow. 

Oxygen Transport. The most widely used methods for measuring oxygen transport are based upon the Ox-Tran instmment (Modem Controls, Inc.). Several models exist, but they all work on the same principle. The most common apphcation is to measure the permeabihty of a film sample. Typically, oxygen is introduced on one side of the film, and nitrogen gas sweeps the other side of the film to a coulometric detector. The detector measures the rate that oxygen comes through the film. The detector response at steady state can easily be converted to At (eq. 1). Simple... 

Such effects principally cannot be observed in multi band detectors such as a UV diode array detector or a Fourier transform infrared (FTIR) detector because all wavelengths are measured under the same geometry. For all other types of detectors, in principle, it is not possible to totally remove these effects of the laminar flow. Experiments and theoretical calculations show (8) that these disturbances can only be diminished by lowering the concentration gradient per volume unit in the effluent, which means that larger column diameters are essential for multiple detection or that narrow-bore columns are unsuitable for detector combinations. Disregarding these limitations can lead to serious misinterpretations of GPC results of multiple detector measurements. Such effects are a justification for thick columns of 8-10 mm diameter. 

Proportional detectors measure the process condition, which can then he compared hy the controller with the required value. They are not direct acting, and need a controller to convert the signal to a working instruction to the controlled device. Proportional detectors include ... 

We take intensity I to mean x-ray quanta per second measured by a detector. An instantaneous detector measures / directly that is, the detector gives a reading always proportional to intensity over the linear range of the detector. The reading could appear on an ammeter after suitable amplification. 

So far we have been concerned with a single detector measuring only the y-component of the magnetization. In such a single-detection system... 

Quadrature detection A method for detecting NMR signals that employs two phase-sensitive detectors. One detector measures the jc-component of... 

Differential refractive index detectors measure the difference in refractive index between the solvent and the eluting polymer solution. The DRI can be used with almost any polymer-solvent combination, as long as the incremental increase in refractive index of the polymer solution with increase in polymer concentration is sufficient. Although a large number of differential refractometers are available in the market,167168 they usually conform to three main types, namely... 

Most physicians do not test for americium in their offices, but they can collect samples and send them to special laboratories. Since americium is radioactive, it is normally measured by its radiation emissions. These emissions are used to tell the amount of americium (in curies or Becquerels) and the radiation dose it gives to your body (in Sieverts or rem). Radiation detectors measure the radiation that is released from objects or materials, including the whole body. If... 

The major attribute that distinguishes planar techniques from column chromatography is that in the former separation and detection are discontinuous ( offline )- In column chromatography analytes are carried through the entire column and monitored at the end, usually by flow-through detectors measuring changes in some physical characteristics of the effluent (optical... 

Electrochemical detectors measure either the conductance of the eluent, or the current associated with the oxidation or reduction of solutes. To be capable of detection, in the first case the solutes must be ionic and in the second case the solutes must be relatively easy to oxidise or reduce. 

The X-ray detector measures the intensity of electromagnetic waves, i.e., the absolute square 2 of their amplitude. Thus, in combination, the upper path between density and intensity through the square is written as... 

Improving Bare-TVack-Detector Measurements of Radon Concentrations... 

YONEHARA ET AL. Improving Bare- Track-Detector Measurements... 

Fig. 5.37 Commercial two-channel infrared C02-detector. Measurement range 300 to 2000 ppm, accuracy +100 ppm (STEI-NEL Solutions AG).

Mass spectrometry can be used to measure the molar mass distribution (MMD) of a polymer sample by simply measuring the intensity, Nt, of each mass spectral peak with mass m . This is due to the fact that mass spectrometers are equipped with a detector that gives the same response if an ion with mass 1 kDa or 100 Da (actually any mass) strikes against it. In other words, the detector measures the number fraction and this implies that Nt also represents the number of chains with mass m,. Thus, the number-average molar mass, Mn, is given by ... 

At this point we ought to hold our breath if 999 photons per 1000 are absorbed (with only one being transmitted), then the detector measuring the intensity of the transmitted light I needs to be exceptionally sensitive. Stated another way, an absorbance of A = 3 is unlikely to be particularly accurate. 

A conductivity detector measures the electrical conductivity of the HPLC eluent stream and is amenable to low-level determination (ppm and ppb levels) of ionic components such as anions, metals, organic acids, and surfactants. It is the primary detection mode for ion chromatography. Manufacturers include Dionex, Alltech, Shimadzu, and Waters. 

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