Double-sampling

Example 2 Calculation of Error with Doubled Sample Weight, , , , 19-5... 

Example 2 Calculation of Error with Doubled Sample Weight Repeated measurements from a lot of anhydrous alumina for loss on ignition established test standard error of 0.15 percent for sample weight of 500 grams, noting V is the square of s.e. Calculation of variance V and s.e. for a 1000 gram sample is... 

What is the largest true mean that complies for u = 4 (double sampling, two determinations for each sample) ... 

A slight modification of the pilot study is a double-sampling plan for estimation (9,10). Double-sampling plans were developed to provide estimates with a fixed precision using as few observations as possible. If the sources of variation and variance components are known prior to the study, then a fixed sample size plan is the best... 

In a double-sampling plan, a small initial sample (ni ) is selected. Variance components are estimated from the results of these samples and then these estimates are used to estimate the total sample required (n). An additional n-i samples are then collected to complete the study. 

The size of the initial sample is an important consideration in a double-sampling plan. The initial sample should be as large as practicable with the constraint that only a small chance exists that... 

Beckers EJ, Rehrer NJ, Saris WHM, Brouns F, Hoor FT, Kester ADM. Daily variation in gastric emptying when using the double sampling technique. Med Sci Sports Exerc 1991 23(101 1210-1212. 

It is always recommended to take double samples and keep one as a backup sample. These can be used in case of doubt concerning the obtained results. 

Example 2 Calculation of Error with Doubled Sample... 

For seal burn, it will be demonstrated with 90% confidence that the defect rate is below 5% defective at the worst-case condition. The double sampling plan for proportion nonconforming nl = 50, al = 0, rl = 2, n.2 = 75, and a2 = 2 can be used for this purpose. This plan requires 50 samples initially. If there are no seal bums, it passes. If there are two or... 

Seal burn 90% confidence Double sampling plan Defect rate... 

Two different schemes are used for modulation chopper stabilization, which works similarly to an AM radio, and correlated double sampling (CDS), which performs two measurements of the noise only and the noise plus signal [19]. Fig. 6.1.11 shows conceptual diagrams of the two techniques. Although the additional circuitry looks complex, actual implementations are surprisingly simple [20, 21]. 

Fig. 6.1.11 Modulation techniques a) chopper stabilization, b) correlated double sampling...

Various circuits are used to simulate a large resistor with active components that take up significantly less chip area. A particularly simple solution consists of a switch that periodically charges the sense capacitors to a known value. This solution can be conveniently implemented in combination with correlated double sampling. Since the sensor capacitance is often small, the noise aliased by this resetting can be significant [22]. 

A monolithic three-axis accelerometer with three independent capacitive readout circuits on a single chip is described elsewhere [7] (Fig. 6.1.14). The circuit is similar to Fig. 6.1.10 and achieves 0.085 aF/v/Hz resolution with 100 fF sense capacitors. The noise is actually dominated by Brownian noise in the sensor itself, as tests in vacuum demonstrate. The actual capacitance resolution is therefore somewhat better than stated. This circuit uses correlated double sampling (CDS) for biasing and to reject flicker noise. 

Fig. 6.1.15 Timing of correlated double sampling (CDS) a) circuit reset, b) sampling noise cancellation, c) sensing...

Many other integrated solutions are documented in the literature. These include single-ended and differential solutions employing chopper stabilization [1, 20, 24, 31], circuits using correlated double sampling [2, 3, 32] and applications for capacitive readout circuits and corresponding implementations [15]. 

Acceptance sampling schemes are based on the Dodge and Romig tables, Military standard 105E or BS 6001. Single or double sampling may be employed. 

A third type of application of this double sample injection valve utilizes a packed reactor, placed in the reagent loop (cf. Fig. 5.10d). This con-... 

The final configuration (Fig. 5.9) allows double sample injection, which can be used for similar purposes as the previous configuration or for injection of two different reagents. Thus a triple zone, very rich on information (which advantageously might be decoded with the aid of che-mometrics) is obtained by a mutual dispersion of sample and reagents in an inert carrier stream. 

This technique has other advantages compared with TLC and HPTLC, e.g. high-speed sample development, low consumption of eluant and reduced diffusion of analyte spots. Newman-Howells Associates and Supelco market horizontal sandwich chambers which are overpressurised in the latter system the chromatoplates can be eluted simultaneously from both ends, thus doubling sample throughput. 

Due to the dc sweep a stationary concentration profile is built up in the thin layer cell. The effect of this profile is eliminated in the dpv technique by the double sampling of the current and therefore only the current sample taken at the end of the pulse is actually measured. There is no time for redox cycling during the pulse duration, as was proved for the npv-polarization. The dpv excitation has several analytical advantages ... 

Dodge HF, Romig HG (1998) Sampling inspection tables single and double sampling, 2nd edn. Wiley, New York... 

Fig. 6.7. Circuit for correlated double sampling. The preamplifier input voltage is reset to V , and the output voltage to zero by closing and then opening the reset switch. The charge is then transferred and the output voltage is sampled. With this approach the output measures only the change in voltage caused by the charge transfer operation. kTC voltage noise caused by the reset operation is not transmitted to the output...

If correlated double sampling is not used, besides background noise the most important source of noise for the series-parallel scan CID is likely to be kTC noise. If this is the case then the maximum signal frequency for which we can design the device to obtain BLIP operation will be... 

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