Noise considerations

Aside from the considerations relating to the selective chemistry of a sensor, the characteristic that most influences the degree to which a sensor can discriminate between one concentration level and another is the signal to noise 

It would be premature to suggest that optimization of the signal to noise ratio for this type of chemical sensor could be done entirely theoretically. Careful sensor design with respect to electrical and thermal shielding are 

Bowers and P.W. Carr, Immobilized Enzymes in Analytical and Clinical Chemistry, John Wiley, New York (1980). 

Fundamentals of Electrochemical Analysis, Ellis Horwood, Chichester (1976). 

---

Lowering the inlet velocities and providing proper inlet silencers can reduce air noise. Considerable work by NASA on compressor casings has greatly reduced noise. 

Signal-to-noise considerations make most neutron-based explosive detection approaches very difficult to implement. The basis for combining multiple detection approaches (FNA, along with thermal gamma detection and neutron transmission spectroscopy) in a FNAP application that preserves the small volume advantage of a APSTNG remains to be established. There are distinct advantages associated with the API approach, but the concomitant reductions in available neutron flux, issues of tube lifetime, and the intrinsic poor spatial resolution must be taken into consideration for potential applications. 

Location Must be located in an area at some distance from the plant proper. This is necessary for air supply considerations and because of problems associated with fogging and drift from discharging air. Noise considerations also tend to dictate site selection. Can be built adjacent to plant buildings, on centers 1.5 (d) where d = base diameter, so that piping costs are reduced. Their position must be chosen so as not to interfere with power plant exhaust plumes. 

Spontaneous Raman spectroscopy has the ability to provide clinically relevant chemical concentration measurements of multiple analytes in biofluids. Blood serum, whole blood, and urine have all been studied. The detection limit (assuming a few hundred seconds of spectral acquisition) appears, based upon fundamental noise considerations, to be around 0.1 mM for most biochemicals this places several important analytes within reach but certainly precludes... 

IEC 534-8-3 1995 Industrial process control valves Part 8 Noise Considerations... 

In the absence of interferents, the correlation coefficient is equal to 1 and therefore ohy = 1. In this case, the minimum detection error is defined solely on the basis of signal-to-noise considerations. When interferents exist, the correlation coefficient is always smaller than 1 and therefore olf is always larger than 1. The minimum detection error approaches infinity when there is complete overlap and the analyte signal is indistinguishable from interfering components. 

S = 22). Moreover, application of noise considerably expands the range of irregular patterns. Indeed, several more significant noise effects have been observed in such simulations which can be of relevance for the disease progression and eventually also for its treatments [3, 25, 26]. 

This sensitivity is, of course, the precision of the measurement based on signal noise considerations, and it does not reflect the absolute accuracy of the measurement. As with other noncontact, nondestructive methods, the thermal-wave technique provides an indirect measure of the geometric film thickness, and absolute accuracy must rely on either an accurate knowledge of the relevant physical parameters, or, as is common with the other methods, the use of calibration standards. In analyzing the data presented here we have used a rather complete (and complex) theoretical model to explain our experimental data, and thereby... 

Equation (14) confirms the earlier observations that to maximize resolution, parasitic capacitance must be kept small. In fact, to first order the resolution is proportional to 2CS + Cp. Apparently, thermal noise considerations impose no penalty on a fully integrated sensor with small sense and parasitic capacitance, since resolution improves by the same factor. Only the combination of small sense capacitance and large parasitic (e.g., due to connection to off-chip electronics) suffers from reduced sensitivity. 

The optimum frequency at which to work is going to be dictated by other considerations as well, availability of a suitable source and detector, signal to noise considerations, working temperature and pressure, and the other species to be determined. Bringing cost into the equation does focus the mind on the expense of both sources and detectors and unless there were a particular operational need the spectral region 40-200 GHz would be a likely compromise for most applications (see Section 6.2). 

The Spectrum (Figure 18.41) exhibits two peaks of about 40 MHz width. A major contribution to this is excess micromotion along the trap axis. The data allowed a fit to the theoretical hyperfine spectrum with an uncertainty of 0.45 MHz, limited by measurement noise. Consideration of systematic effects led to a slightly increased... 

A modular power center, commonly found in computer-room installations, provides a comprehensive solution to AC power-distribution and ground-noise considerations. Such equipment is available from several manufacturers, with various options and features. A computer power-distribution center generally includes an isolation transformer designed for noise suppression, distribution circuit breakers, power-supply cables, and a status-monitoring unit. The system concept is shown in Fig. 10.268. Input power is fed to an isolation transformer with primary taps to match the AC voltage required at the facility. A bank of circuit breakers is included in the chassis, and individual preassembled and terminated cables supply AC power to the various loads. A status-monitoring circuit signals the operator if any condition is detected outside normal parameters. 

FIGURE 12.28 Receiver noise considerations (a) demodulator using RF bandpass filter showing where SNRj and SNR, are measured, (b) received signal spectrum, (c) bandpass output spectrum. 

Keicz F, Joseph PM, Hilal SK (1979) Noise considerations in dual energy CT scanning. Med Phys 6 418-425... 

Most of the compromise factors discussed in reference to thermocouples apply equally to bolometers. In addition, the previously discussed noise considerations apply equally well to metal bolometers whose primary source of noise is Johnson noise. The resistance of commercially available metal bolometers is 30-100 ohms. Response times are comparable to those of commonly available thermocouples. 

---