Calibration self-calibrating

A final practical note involves instrument intensity measurement calibrations. The intensity measurement is self-calibrating relative to the incident beam from the source. However, measurements typically have a dynamic range of 10 -10 , and care must be taken to insure the detection system is linear. A method of calibrating the scatterometer is to characterize a diffuse reflector having a known scattering characteristic. For example, a surface coated with BaS04 makes a nearly Lambertian scatterer, which has a BRDF of 1/Jt at all angles. 

The advanced control room uses fiber optics, microprocessors, and digital monitoring and control. This includes self-testing, automatic calibration, user interactive from panels, full multiplex, standardization of the man-machine interface, common circuit cards, and wide-range flux monitors to eliminate range switching on startup. 

A calibration facility must produce the desired velocity range for the meter to be calibrated. The air temperature should be kept constant over the test to ensure constant density. For thermal anemometers, velocity calibration only is not sufficient. They should also be checked for temperature compensation. In the case of omnidirectional probes, sensitivity to flow direction should be tested. In the case of low-speed (thermal) anemometers, their self-convection error should be measured, and, for instruments measuring flow fluctuation (turbulence), dynamic characteristics testing should be carried out as well. ... 

Some electronic equipment has self-calibration routines built in to the start-up sequence. This should be taken as an indication of serviceability and not of absolute calibration. The device should still be subject to independent calibration at a defined frequency. 

The records required are only for formal calibrations and verification and not for instances of self-calibration or zeroing using null adjustment mechanisms. While calibration usually involves some adjustment to the device, non-adjustable devices are often verified rather than calibrated. However, as was discussed previously, it is not strictly correct to regard all calibration as involving some adjustment. Slip gages and surface tables are calibrated but not adjusted. An error record is produced to enable users to determine the uncertainty of measurement in a particular range or location and compensate for the inaccuracies when recording the results. 

The primary reason for die popularity of the Pople and DH style basis sets is the extensive calibration available. There have been so many calculations reported with these basis sets that it is possible to get a fairly good idea of the level of accuracy that can be attained with a given basis. This is of course a self-sustaining procedure, the more calculations that are reported with a given basis, tlie more popular it becomes, since the calibration set becomes larger and larger. 

Self-calibration and/or testing according to predetermined programming. 

Self-Tfst 6.4B A calorimeter was calibrated by mixing two aqueous solutions together, each of volume 0.100 L. The heat output of the reaction that took place was known to be 4.16 kj, and the temperature of the calorimeter rose by 3.24°C. 

What if instruments could be designed which were remoteiy self-calibrating with respect to calibration services of a National Metrology Institute (NMI) While this may sound very far-fetched , it is not difficult to speculate that future application of telemetry, transducers, intrinsic standards, detectors and computers will link some instruments directly to a NMI to obviate their need for RMs (Rasberry 1998). 

One of the limitations of the portable field survey instruments in the measurement of americium is that their quantitative accuracy depends on how well the lateral and vertical distribution of americium in the soil compares with the calibration parameters used. These methods can provide a rapid assessment of americium levels on or below surfaces in a particular environment however, laboratory-based analyses of samples procured from these environmental surfaces must be performed in order to ensure accurate quantification of americium (and other radionuclides). This is due, in part, to the strong self absorption of the 59.5 keV gamma-ray by environmental media, such as soil. Consequently, the uncertainty in the depth distribution of americium and the density of the environmental media may contribute to a >30% error in the field survey measurements. Currently, refinements in calibration strategies are being developed to improve both the precision and accuracy (10%) of gamma-ray spectroscopy measurements of americium within contaminated soils (Fong and Alvarez 1997). 

Houben [256] has compared the determination of flame-retardant elements Br, P, S, K, Cl and F in polycarbonate using commercial (X40 and UniQuant ) software. For the X40 method, a calibration line for each element in PC or PC/ABS blends was mapped for the conversion of intensities to concentrations. With the universal UniQuant method, sensitivity factors (ks) were calibrated with pure standards. The X40 method turned out to be more reliable than UniQuant for the determination of FRs in PC and PC/ABS blends, even in the case of calibration of k values with PC standards. Standard errors of 5 % were achieved for Br, P, S and K, and 20% for Cl and F the latter element could not be determined by means of UniQuant (Table 8.44). GFR PC cannot be quantified with these two methods, because of the heterogeneous nature of the composites. Other difficult matrices for XRF analysis are PBT, PS and PP compounds containing both BFRs and Sb203 (10-30wt %) due to self-absorption of Sb and interelement effects. 

FRET to fluorescent acceptor is obviously more popular because of its two-channel self-calibrating nature. Sensing may result in switching between two fluorescent states, so that in one of them a predominant emission of the donor can be observed and in the other - of the acceptor. This type of FRET can be extended to time domain with the benefit of using simple instrumentation with the longlifetime donors [27]. 

Demchenko AP (2005) The problem of self-calibration of fluorescence signal in microscale sensor systems. Lab Chip 5 1210-1223... 

A different approach to design a self-calibrating dye was proposed [70], in which a viscosity-sensitive molecular rotor (2-cyano-3-(4-dimethylaminophenyl) prop-2-enoic acid) was covalently linked to a reference dye, 7-methoxycoumarin-3-carboxylic acid, which exhibited no viscosity sensitivity (40, Fig. 13). A ratiometric measurement, that is, rotor emission relative to reference emission, was shown to be widely independent of dye concentration [70]. However, the design of such a ratiometric dye poses some challenges because of resonance energy transfer from... 

Fig. 13 Self-calibrating dyes DMA-2,4 and p-A,A-dimethylaminobenzoic acid. Compound 40 is an engineered ratiometric dye composed of a viscosity-sensitive molecular rotor and a nonviscosity-sensitive reference dye [70]...

TCSPC is inherently self-referenced and therefore, with the exception of the regular recording of the IRF, a TCSPC system requires practically no day-to-day calibration. In TCSPC the recording... 

The observations were performed at ESO using the 1.52m telescope and FEROS. The obtained spectra have high nominal resolving power (R 48000), and S/N 500 at maximum and a coverage from 4000 A to 9200 A. Many spectra were acquired for all sample stars. The atmospheric parameters (Teff, log g, [Fe/H] and microturbulence velocities) have been obtained through an iterative and totally self-consistent procedure from Fe lines of the observed spectrum. The initial values of Teg were obtained from a (B-V) vs Teg calibration and log were determined from Hipparcos parallaxes and evolutionary tracks. The [O/Fe] abundances were derived by fitting synthetic spectra to the observed one. 

Bulajic D., Corsi M., Cristoforetti G., Legnaioli S., Palleschi V., Salvetti A., Tognoni E., A procedure for correcting self-absorption in calibration-free Laser Induced Breakdown Spectroscopy, Spectrochimica Acta B 2002 57 339-357. 

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