Special calibration measurements

In order to allow quantitative studies of the influence of PCI, detailed information on the performance of the electron spectrometer is required. This includes the spectrometer factor /, the energy shift caused by contact potentials (the c value introduced in equ. (4.56c)), the correct shape of the spectrometer function, and 

According to equ. (4.56b) the PCI-modified actual energy kin of the electrons differs from the value which can be extracted from the spectrometer voltage at peak maximum, Usp, multiplied by the spectrometer factor /, due to the presence of a contact potential c  

an accurate value for the photon energy ph follows, using the right-hand part of these equations and taking their difference  

The shape observed for the Auger line results from the convolution of the 

A sp = 204 meV is obtained which corresponds to (A / )sp — 0.68%. (The photon beam diameter was estimated to be approximately 2 mm according to the ray-tracing results shown in Fig. 4.13 this corresponds to (A / )sp = 0.64%.) Keeping fixed values for T and A sp, it is then possible to analyse the Auger lineshapes obtained at other, in particular lower, photon energies correctly. 

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All the special cases that may be appear in analytical calibration in dependence from the specific conditions as well as the uncertainties of the calibration measures will be given in the following. 

Pump tubes are available in different materials depending on the liquid to be pumped, e.g. for solvents or concentrated acids. Flow rates for these other materials will be different than for standard PVC. Pump tubes may also be available in a specially calibrated or measured flow rate quality at extra cost. Unless specified for medical purposes or to meet regulations, the standard quality is normally adequate. See Chapter 1, Peristaltic pumps. ... 

The cryogenic adsorption system was specially developed to measure adsorption isotherms of H2 and D2. This system is equipped with a closed helium cycle two-stage Gifford McMahon refrigerator to operate under cryogenic conditions. The adsorption temperature can be kept constant within 0.03 K at 20 K. Adsorption isotherms are obtained by gas adsorption manometry. This method is based on the measurement of the gas pressure in a calibrated, constant volume, at a known temperature. The dead space volume was calculated from a helium calibration measurement at the temperature of interest. Thermal transpiration effect was calibrated according to the work by Takaishi and Sensui [41]. 

For volumetric measurements with piston-cylinder devices at pressures up to 2 GPa much experience and special calibrations are required. ... 

After the cryostat is installed in the machine, the sample is loaded statically as determined by the deflection of the calibrated load lever. This deflection is measured with a special calibration bar which incorporates a dial indicator. 

Microbalances are often used to measure single component adsorption isotherms. Measurements are possible in the pressure range between 1 and lo Pa (Akgiin 2007). The partial pressure of oiganic adsorptives can be adjusted by means of a bubble flask in combination with a condenser (Scholl 1991). As a rule gas concentrations are measured by gas chromatographs equipped with special calibrated analyzers. Multicomponent adsorption equihbria can be determined by... 

The determination of riser and downcomer [/l is often accomplished using a tracer technique or specially calibrated flow meters and mathematical relationships to convert the measurable Vl to I/l- The tracer techniques commonly used to determine Vl are based on determining the time it takes for a given tracer to travel a set distance. For example, a potassium chloride salt tracer and conductivity electrodes are commonly used to measure the time it takes an injection of the salt solution to travel past two fixed locations from which Vl is calculated (Bello et al.. 

Direct microscopic count A method of measuring bacterial growth by counting cells in a known volume of medium that fills a specially calibrated counting chamber on a microscope slide. 

Under the experimental conditions and due to the short time of transverse relaxation of proton in solids, the contribution of protons from ice and surface hydroxyls to the recorded NMR signal can be neglected. Only the signal from mobile water molecules remaining unfrozen (due to the interaction with the carbon surface or solute molecules and ions) at temperature below 273 K was measured. The amount of unfrozen water bound to carbon surface and protein molecules is temperature-dependent. It was determined from the ratio of signal intensities before and after freezing using a special calibrated function. The total amount of water in each sample was constant (2 mL). 

A number of photographs illustrate typical measurement situations. A collimated detector, detector hoist, and cart-mounted readout were usually used. A compact, hand-held Instrument was also used extensively. Some special calibration source arrangements were made to simulate some of the more common situaUons encountered in Hie measurements. 

If the first derivative of e (i. e., de/dA) is equal to zero, the second derivative will be directly (linearly) proportional to the concentration. Otherwise no linear relation is found, and a special calibration curve will be necessary. In addition, for extreme values of d e/dA, the sensitivity of the measurement is particularly high. 

The hardness is generally measured with a Shore model C-2 Scleroscope with a specially calibrated diamond-tip hammer.f l... 

High mass resolution of ToF-SIMS instruments (10 to 10 amu) enables exact mass measurements, calculation of empirical formulae and more reliable unknown peak identification [130]. Accurate mass determination by ToF-SIMS is very simple because no special calibration procedures or calibration standards are required. The accuracy is about 10 ppm for atomic species and for molecules in the low mass range. For organic molecules in the high mass range an accuracy better than 5 ppm was obtained. In cases where the mass resolution is not sufficient, mass spectral fragmentation patterns may be compared to library spectra for identification. 

Specially calibrated smart digital pressure transmitters are now available to provide much better acctnaty. The onboard microprocessor allows compensation for temperature effects and systematic transmitter deviations. HTG makes use of these accurate pressure transmitters for a continuous mass measurement of the tank contents (Fig. T-12). 

Mindful of the scientific importance of low-error photometric measurements, we are making a special effort in determining ARNICA s photometric characteristics. As a rule, for eadi photometric calibration measurement we place the calibration star in five different positions of the field. Also, in order to better appreciate the difference in spatial response, we placed standard stars in 64 different locations arranged as a square grid, in each of three bands. 

It is critically important for instrument users to understand what their instmment sensors can and cannot properly measure. Specific conditions and hazards may require the use of specialized sensors, or a specialized calibration strategy that will provide more accurate readings for the gases actually present. 

Flow measurements using tracers are performed in all piping systems carrying oil, gas or water including separators, compressors, injector systems, and flares. Calibration of elsewhere difficult accessible flow meters is regularly performed by the tracer methods, which are based on international standards. Tracer flow measurements are also well suited for special purposes... 

Measurement of the conductivity can be carried out to high precision with specially designed cells. In practice, tiiese cells are calibrated by first measuring the conductance of an accurately known standard, and then introducing the sample under study. Conductances are usually measured at about 1 kHz AC rather than with DC voltages in order to avoid complications arismg from electrolysis at anode and cathode [8]. 

Cahbration of some measurement devices involves comparing the measured value with the value from the working standard. Pressure and differential pressure transmitters are calibrated in this manner. Calibration of analyzers normally involves using the measurement device to analyze a specially prepared sample whose composition is known. These and similar approaches can he applied to most measurement devices. 

Over the last seventeen year s the Analytical center at our Institute amassed the actual material on the application of XRF method to the quantitative determination of some major (Mg, Al, P, S, Cl, K, Ti, Mn, Fe) and trace (V, Cr, Co, Ni, Zn, Rb, Sr, Y, Zr, Nb, Mo, Ba, La, Ce, Pb, Th, U) element contents [1, 2]. This paper presents the specific features of developed techniques for the determination of 25 element contents in different types of rocks using new Biaiker Pioneer automated spectrometer connected to Intel Pentium IV. The special features of X-ray fluorescence analysis application to the determination of analyzed elements in various types of rocks are presented. The softwai e of this new X-ray spectrometer allows to choose optimal calibration equations and the coefficients for accounting for line overlaps by Equant program and to make a mathematic processing of the calibration ai ray of CRMs measured by the Loader program. 

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