Detectors electronic noise

The NEP may be written in terms of the detector element active area, the number of detector pixels elements cormected for additive output the electronic noise bandwidth B and the detector element detectivity, D. Typically = 1, but may be increased for improved sensitivity with an attendant loss in resolution. 

The fact that we have peaks within a 2D space implies that where no peak is found represents a true detector baseline or electronic noise level. In a conventional petroleum sample, a complex unresolved mixture response causes an apparent detector baseline rise and fall throughout the GC trace. It is probably a fact that in this case the true electronic baseline is never obtained. We have instead a chemical baseline comprising small response to many overlapping components. This immediately suggests that we should have more confidence in peak area measurements in the GC X GC experiment. 

The IDL is dependent on various factors such as sensitivity of the detector for the analyte of interest and electronic and detector (instrumental) noise of various origins, e.g., thermal noise, shot noise, flicker (1 //) noise, environmenfal noise, efc. Several books and articles have been published on fhe different types of instrumental noise, e.g., Skoog and Leary s Principles of Instrumental Analysis . ... 

A problem encountered with atomic absorption is that emission from the flame may fall on the detector and be registered as negative absorption. This can be eliminated by modulating the light source, either mechanically or electronically, and using an a.c. detector tuned to the frequency of modulation of the source. D. C. radiation, such as emission from the flame, will then not be detected. A high intensity of emission, however, may overload the detector, causing noise fluctuations. 

In INAA, a rock or mineral sample is irradiated in the reactor. The irradiated sample is removed from the reactor, and the dangerous radioactivities are allowed to decay. Then the sample is placed into a counter and the y-rays emitted by each element in the sample are counted. A variety of counters are used, including scintillation counters, gas ionization counters, or semi-conductor counters. For the most precise results, background counts in the detectors produced by electronic noise, cosmic rays, and other radioactive decays must be eliminated. The technique is very sensitive, and samples as small as a few tens of milligrams can be measured. 

Noise and Drift. Electronic, pump, and photometric noise poor lamp intensity, a dirty flow cell, and thermal instability contribute to the overall noise and drift in the detector. Excessive noise can reduce the sensitivity of the detector and hence affect the quantitation of low-level analytes [13,14]. The precision of the... 

In the experiment, the transmission intensities for the excited and the dark sample are determined by the number of x-ray photons (/t) recorded on the detector behind the sample, and we typically accumulate for several pump-probe shots. In the absence of external noise sources the accuracy of such a measurement is governed by the shot noise distribution, which is given by Poisson statistics of the transmitted pulse intensity. Indeed, we have demonstrated that we can suppress the majority of electronic noise in experiment, which validates this rather idealistic treatment [13,14]. Applying the error propagation formula to eq. (1) then delivers the experimental noise of the measurement, and we can thus calculate the signal-to-noise ratio S/N as a function of the input parameters. Most important is hereby the sample concentration nsam at the chosen sample thickness d. Via the occasionally very different absorption cross sections in the optical (pump) and the x-ray (probe) domains it will determine the fraction of excited state species as a function of laser fluence. 

Intensity of scattered neutrons is measured as a function of scattering angle 20. The measured response of the neutron detector is the sum of the coherent scattered intensity of the sample particles (Eq.2), the scattering from the solvent, the scattering from the sample cell, and the electronic noise in the detector. To obtain the scattering from the sample particles, background scattering due to solvent and sample cell, and noise counts in the detector, must be subtracted from the experimental scattered intensity. The result is normalized to an... 

This third scheme maintains favorable collection geometry (360 ) while minimizing detector background noise by electronically rejecting non-coincident photomultiplier pulses. The detectors described in the present work are applicable to both high-energy 0 emitters and 7 emitters. We report here on their application to the detection of 2P-labeled molecules separated by capillary electrophoresis. ... 

Preamplifiers unavoidably add electronic noise to the signals of the detector. It is of a crucial importance for the development of PSD-systems to make the right choice concerning the preamplifiers. In fact, the art of designing a good detector system hes in the art of designing the best preamplifier for a given purpose. 

The various probe beams can be coupled into the same singlewavelength, dual-channel pulse-probe transient optical absorption set-up. A one-meter-long optical delay line is used to control the variable time delay between the electron and the probe pulses. Approximately half of the probe beam is deflected onto a reference photodiode while the other half of the beam is slightly focused into the sample, which is placed in front of the output window of the accelerator. Subsequently, the probe beam is then transported to the sample photodiode. (Alternatively, in some laboratories the probe and reference beams are transported into the detection room by long, low-OH silica optical fibers in order to reduce electronic noise pickup on the detector signal cables.)... 

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