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. 

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. 

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

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). 

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]...

Wang, A. Xiao, H. Wang, J. Wang, Z. Zhao, W. May, R. G., Self calibrated interferometric intensity based optical fiber sensors, J. Lightwave Technol. 2001, 19, 1495 1501... 

When a fluoroionophore contains two fluorophores whose mutual distance is affected by cation complexation, recognition of this cation can be monitored by the monomer/excimer fluorescence-intensity ratio (see Chapter 4, Section 4.4.1 for ex-rimer formation). Cation binding may favor or hinder exrimer formation. In any case, such a ratiometric method allowing self-calibration measurement is of great interest for practical applications. 

Nd YAG and the lifetime measurement is made by the use of the phase-locked detection of fluorescence lifetime (PLD) scheme. By reference to the use of the fluorescence lifetime measurement, the problems, in pyrometry, of emissivity, and sight path factor in the blackbody radiation measurement could be corrected in such a scheme having an internal self-calibration. ... 

C. SampOT, F. Self-Calibrating Property of MALDI-TOF Spectra of Polymeric Materials. Rapid Commun. Mass Spectrom. 1994, 8,981-984. 

Between periods of servicing of the balance, it is wise to check the accuracy with a calibration weight. Some balances incorporate a self-calibration facility. 

Sandowdki C, Lawler G. A relational data base management system for LIMS. Amer Lab 21(3) 70-79, March 1989. SARTORIOUS. Self-calibrating balances for quality assurance systems. Pharm Mfg Rev 8.5 38, 1996. 

SARTORIOUS. Balances allow self-calibration. Mfg Chem 67.10 87, 1996. 

The geometry of the tube scanner also provides a purely electrical method to self-test and self-calibrate, especially for measuring the piezoelectric constants in a cryogenic environment. The piezoelectric constant varies with temperature in a complicated manner, and also with the particular batch of materials by the manufacturer and time (the aging effect). 

D. Whittaker, PrRoySoc 240A, 54-66(1957) (Determination of arc temperatures from shock velocities) 39) J. Tyroler, "A Self-Calibrating Highspeed Photographic Pyrometer , 6thSympCombstn (1957), p 763-65 40)... 

Even the tight controls in silicon integrated circuit manufacturing are not yet sufficient to produce absolutely identical sensors on a single wafer. Calibration of the final product is usually necessary, often by adjusting the value of a circuit element on the IC such as a resistor. The calibration process can be automated, but it still adds to the cost of batch-fabricated sensors. Clever means of self-calibration, particulady in field use, are constandy being sought. 

On p D597-R of Vol 4, is briefly described a Self-Calibrating Hx gh-Speed Photographic Pyrometer" devised by J. Tyroler of PicArsn. 

FIGURE 8 Self-calibrating image comparison for counterfeit identification score images. White higher score. Black lower score. 

Calibrated. In order for sensors to gain acceptance as deployable measurement tools, they must remain calibrated for extended periods of time (weeks to months) or must be self-calibrating. 

Self-calibrating high-throughput content uniformity measurements... 

But, you say, the equipment is self-calibrating and no record is possible. True and without question, but is it so much to ask that there be a notebook showing day by dc y that the self-calibrating sequence was run through and everything was hunky-dory ... 

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