Dynamic response index

Frequency Weighting. The inverse frequency contour (i.e., reciprocal) to an equinoxious contour should be applied to a stimulus containing many frequencies to produce an overall magnitude that appropriately combines the contributions from each fr uency. The frequency weightings most commonly employed for whole-body and hand-transmitted vibration are shown in Fig. 10.1 (ISO 2631-1,1997 ISO 5349-1, 2001). The range of frequencies is from 1 to 80 Hz for whole-body vibration, and from 8 to 1250 Hz for vibration entering the hand. A frequency weighting for shocks may also be derived from a biodynamic model (see Dynamic Response Index (DRI) in Sec. 10.3.1). 

Thus the slope of the Log/Log curve will give the value of the response index (r). If the detector is truly linear, r = 1 i.e. the slope of the curve will be sin 7r/4 =1). Alternatively, if suitable software is available, the data can be curved fitted to a power function and the value of (r) extracted from the results. The same data can be employed to determine the linear range as defined by the ASTM E19 committee. In this case, however, a linear plot of detector output against solute concentration at the peak maximum should be used and the point where the line deviates from 45° by 5% determines the limit of the linear dynamic range. 

Linear Dynamic Range - (D ) - The linear dynamic range of a detector is that concentration range over which the detector response is linear within defined response index limits. It is also dimensionless and is taken as the ratio of the concentration at which the response index falls outside its defined limits, to the minimum detectable concentration or sensitivity. The linear dynamic range is important when the components of a mixture being analyzed cover a wide concentration range. 

This again emphasizes the need for an improved procedure for defining detector specifications. The linear dynamic range of the electron capture detector is again ill-defined by many manufacturers. In the DC mode the linear dynamic range is usually relatively small, perhaps two orders of magnitude, with the response index lying... 

The sensitivity should be given as that solute concentration that produces a signal equivalent to twice the noise. Such data allows a rational comparison between detectors. The linear dynamic range is also not precisely clear from the original publication but appears to be at least three orders of magnitude for a response index of (r) where 0.97 < r < 1.03, but this is an estimate from the data published. The... 

The out-of-balance signal caused by the presence of sample vapor in contact with the sensor is amplified and fed to a recorder or computer data acquisition system. For maximum sensitivity hydrogen should be used as the carrier gas, but to reduce fire hazards, helium can be used with very little compromise in sensitivity. The sensitivity of the katherometer is only about 10 g/ml (probably the least sensitive of all GC detectors) and has a linear dynamic range of about 500 (the response index being between 0.98 and 1.02). Although the least glamorous, this detector can be used in most GC analyses that utilize packed columns and where there is no limitation in sample availability. The device is simple, reliable, and rugged and, as already stated, relatively inexpensive. 

The detector was claimed to be moderately linear over a dynamic range of three orders of magnitude but values for the response index are not known. It is also not clear whether the associated electronics contained signal modifying circuitry or not. The disadvantages of this detector included erosion of the electrodes due to "spluttering", contamination of the electrodes from sample decomposition and the need for a well-controlled vacuum system. 

As a result of limited sensitivity and restricted linear dynamic range, the refractive index detector is often a "choice of last resort" and is used for those applications where, for one reason or another, all other detectors are inappropriate or impractical. However, the detector has one particular area of application for which it is unique and that is in the separation and analysis of polymers. In general, for those polymers that contain more than six monomer units, the refractive index is directly proportional to the concentration of the polymer and is practically independent of the molecular weight. Thus, a quantitative analysis of a polymer mixture can be obtained by the simple normalization of the peak areas in the chromatogram, there being no need for the use of individual response factors. The sensitivity of most RI detectors will be about 1 x 10 g/ml and the linear dynamic range around 1 x 10 to 2 X 10 4 g/ml with the response index (r) lying between 0.97 and 1.03. 

The device functions in the same way as the conventional electron-capture detector with a radioactive source. The column eluent enters just below the third electrode, any electron-capturing substance present removes some of the free electrons, and the current collected by the fourth electrode falls. The sensitivity claimed for the detector is 0.2-1.0 ng, but this is not very informative as its significance depends on the characteristics of the column used and on the k of the solute peak on which the measurements were made. The sensitivity should be given as that solute concentration that produces a signal equivalent to twice the noise. Such data allow a rational comparison between detectors. The sensitivity or minimum detectable concentration of this detector is probably similar to the conventional pulsed ECD (viz. 1 X 10 g/mL). The linear dynamic range appears to be at least three orders of magnitude for a response index of r, where 0.97 [Pg.607]

The sensitivity of the katharometer is only about 10 g/mL (probably the least sensitive of all GC detectors) and has a linear dynamic range of about 500 (the response index lying between 0.98 and 1.02). It is, however, a general detector and will sense all permanent... 

The linear dynamic range (DJ of a detector is that range of solute concentration over which the numerical value of the response index falls within defined limits. For example, the linear dynamic range of a detector such as the FID might be specified as... 

Thus, (2.5) provides a ranking of all k elements relative to the total energy flowing through all the elements in the system. It is proposed that an element with a low activity index has a small contribution to the system dynamic response, thus it is unnecessary under the given scenario and, therefore, can be eliminated from the model to generate a reduced model. This elimination procedure is described in Section 2.3. 

The desired (dDOpS) and achievable (dAOpS) dynamic operating spaces can be compared to define a dynamic Operability Index (dOI) as the fraction of the operating ranges that can be achieved within the desired response time t (ysp, d) given the available input ranges in dAIS. To aid us in defining the operability index mathematically, two additional spaces are introduced. The first operating space, referred to as Si, is the space obtained by the combination of the set points in DOS and disturbances in EDS ... 

The first reported concentration is usually that which will provide a signal equivalent to twice the noise level and the second reported concentration is the limit at which the response factor was determined. At present, manufacturers do not usually differentiate between D and and do not quote a range for the response index r, however, it is hoped that in the future such data will be made available. Some manufacturers do mark the least sensitive setting of the detector as non-linear (N/L), which is a step towards a more rational approach to specifying linetu dynamic range. 

The linear dynamic range of the system was shown to be about four orders of magnitude as indicated by the curve in Figure 18. The response index determined for a series of compounds of different chemical types was found to be between 0.96 and 1.04. 

Quantitative analysis by LC, as opposed to qualitative analysis imposes stringent demands on the performance of the detector. Consequently, for accurate quantitative analysis the detector must have a linear response (or a known response index) and must be operated within its linear dynamic range further, the baseline noise must be minimal if peak area measurements are to be employed. The basic measurements employed for quantitative analysis are peak heights or peak areas. In general analysis, peak heights tends to give more precise results than peak areas. 

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