Detecter noise

There are several strategies and tools that can be used to assess, and subsequently minimize, such sampling-based errors in the calibration data. The use of replicate samples in the calibration experiment can help to detect noise issues around instrument... 

The calibration sensitivity does not indicate what concentration differences can be detected. Noise in the response signals must be taken into account to be quantitative about what differences can be detected. For this reason, the term analytical sensitivity is sometimes used. The analytical sensitivity is the ratio of the calibration curve slope to the standard deviation of the analytical signal at a given analyte concentration. The analytical sensitivity is usually a strong function of concentration. 

Figure 1.13 Signal vs. wavelength with different noise levels (a) no detectable noise, (b) moderate noise, and (c) high noise.

In choosing photodetectors for optical sensors, a number of factors must be considered. These include sensitivity, detectivity, noise, spectral response, and response time. Photomultipliers and semiconductor quantum photodetectors, such as photoconductors and photodiodes, are all suitable. The choice, however, is somewhat dependent on the wavelength region of interest. Generally, both types give adequate... 

The decibel is the ratio of measured noise level to minimum detectable noise level. 

If the frequency spectrum 1(f) of the detector signals is measured with a spectrum analyzer at sufficiently high frequencies /, where the technical noise is negligible, one obtains a noise power spectrum Pn(/), which is essentially independent of the phase 0 (Fig. 14.62b), but depends only on the number of photons entering the interferometer. It is proportional to /N. It is surprising that the noise power density Pn(f) of each detector is independent of the phase 0. This can be understood as follows the intensity fluctuations, because of the statistical emission of photons, are uncorrelated in the two partial beams. Although the mean intensities I ) and I2) depend on 0, their fluctuations do not The detected noise power pn oc Va shows the same noise level pn oc for the minimum of 7(0) as for the maximum (Fig. 14.62b). 

Detection noise is signal independent and therefore additional detectors will increase the total noise of a measurement. This is not the case for the Poisson distributed noise of the emission light (photon shot noise), a significant factor for weak fluorescence signals. It is not significantly affected by the number of... 

The Probability of Correct Detection used in Fig. 21 is defined as the ratio of the number of correctly detected spikes over the number of total neural spikes. The Probability of False Detection is defined as the ratio of the number of detected noise events over the number of total detected spikes. For example, if the number of neural spikes is 100 and the detector detects 120 spikes, among which 99 spikes are neural spikes and 21 events are noise, the Probability of Correct Detection is 99=100 and Probability of False Detection is 21=120. With NEO-based spike detection, the detection threshold hold is set to be three times of the RMS score, which corresponds to 1 4% error detection and detects 99 5% spikes as a worst case in this data set (detailed information is shown in Table 6). The detected spike with interval less than 1.2 ms are treated as overlapping events and ignored. It is worthy to clarify that a reduction of the minimal spike internal increases the error probability. 

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