Signal-to-noise ratio measurement

Signal-to-noise ratio measured at conditions wavelength (A) = 800 nm, carrier frequency (/) = 1 MHz, linear velocity of the disk (t ) = 5 m/s, bandwidth (BW) = 30 kHz, unless otherwise noted. 

Note Since all measurements are made relative to a blank, the baseline noise is very small and leads to an artificially low detection limit based on a signal-to-noise ratio measurements. The detection limit therefore must be determined by visual inspection of diluted standards. 

In order to maximize the excitation, precautions have to be taken to avoid cross-talk between excitation and signal. Therefore differential probes are commonly used with a SQUID system Nevertheless, for the discussed defects the SQUID system has a lower excitation field by a factor of about 100 compared with the commereial system This we must keep in mind, when we compare measured signal to noise ratios. There is a potential to improve for small defeets, when eross-talk is managed very well. 

Based upon a piezoelectric 1-3-composite material, air-bome ultrasonic probes for frequencies up to 2 MHz were developped. These probes are characterized by a bandwidth larger than 50 % as well as a signal-to-noise ratio higher than 100 dB. Applications are the thickness measurement of thin powder layers, the inspection of sandwich structures, the detection of surface near cracks in metals or ceramics by generation/reception of Rayleigh waves and the inspection of plates by Lamb waves. 

For the sake of illustration, a TOF analyzer could be likened to a camera taking snapshots of the m/z values of an assembly (beam) of ions the faster the repetition rate at which the camera shutter is clicked, the greater is the number of mass spectra that can be taken in a very short time. For TOF analyzers, it is not uncommon to measure several thousand mass spectra in one second All such spectra can be added to each other digitally, a process that improves the signal-to-noise ratio in the final accumulated total. 

The sensitivity equation can be developed by differentiating equation 4 with respect to J. Since the signal is proportional to J and detection is defined as to when the measured signal to noise ratio equals 3, the gas detection sensitivity (ppm) in terms of the NEP for gas detection becomes ... 

A study was conducted to measure the concentration of D-fenfluramine HCl (desired product) and L-fenfluramine HCl (enantiomeric impurity) in the final pharmaceutical product, in the possible presence of its isomeric variants (57). Sensitivity, stabiUty, and specificity were enhanced by derivatizing the analyte with 3,5-dinitrophenylisocyanate using a Pirkle chiral recognition approach. Analysis of the caUbration curve data and quaUty assurance samples showed an overall assay precision of 1.78 and 2.52%, for D-fenfluramine HCl and L-fenfluramine, with an overall intra-assay precision of 4.75 and 3.67%, respectively. The minimum quantitation limit was 50 ng/mL, having a minimum signal-to-noise ratio of 10, with relative standard deviations of 2.39 and 3.62% for D-fenfluramine and L-fenfluramine. 

The minimum detectable limit depends on the analytical range, span, and signal-to-noise ratio of the measurement system. For a well-designed system, the minimum detectable limit should be less than 2 percent of the span. 

Thorinm-232 is the only non-radiogenic thorium isotope of the U/Th decay series. Thorinm-232 enters the ocean by continental weathering and is mostly in the particulate form. Early measurements of Th were by alpha-spectrometry and required large volume samples ca. 1000 T). Not only did this make sample collection difficult, but the signal-to-noise ratio was often low and uncertain. With the development of a neutron activation analysis " and amass spectrometry method " the quality of the data greatly improved, and the required volume for mass spectrometry was reduced to less than a liter. Surface ocean waters typically have elevated concentrations of dissolved and particulate 17,3 7,62... 

In most cases, closed-loop control can be improved by moving the surge control line to a more conservative position in response to disturbances. When the flow measurement is sufficiently stable (good signal-to-noise ratio), the controller can calculate the time derivative of the compressor map. 

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