Detector dynamical range

D. S. Simons. Int. J. Mass Spectrom. Ion Process. 55,15,1983. General discussion of the OMS technique and its applications. Contains a discussion of detector dynamic range issues. 

Manufacturer Instrument Light source Excitation A (nm) Emission A (nm) Detector Dynamic range Temperature reference Design Application... 

Detector Linearity Linear Dynamic Range Detector Noise Level... 

The dynamic range of LC detectors is usually considerably less than their GC counterparts which evinces more care in determining sample size in quantitative analysis. A GC detector may have a linear response over a concentration range of five or six orders of magnitude, for example, the flame ionization detector, whereas an LC detector is more likely to have a dynamic range of only three orders of magnitude and some detectors considerably less. 

In many ways, today s optical and infrared detectors are nearly perfect, with high quantum efficiency, low readout noise, high dynamic range and large arrays of pixels. However, as good as the detectors are, there are limitations that must be understood and respected in order to produce the best astronomical instm-ments and thereby, the best science. 

It is usually recognized that general detectors are less sensitive than specific detectors, have a lower dynamic range (see below) and do not give the best results when gradient elution is used. 

There are a number of properties of a detector that determine whether they may be used for a particular analysis, with the most important being (a) the noise obtained during the analysis, (b) its limit of detection, (c) its linear range, and (d) its dynamic range. The last three are directly associated with the analyte being determined. 

When the linear range is exceeded, the introduction of more analyte continues to produce an increase in response but no longer is this directly proportional to the amount of analyte present. This is referred to as the dynamic range of the detector (see Figure 2.6). At the limit of the dynamic range, the detector is said to be saturated and the introduction of further analyte produces no further increase in response. 

It is important for obtaining precise results that the signals from the samples to be determined should lie on the linear part of the calibration graph as elsewhere within the dynamic range a small change in detector response corresponds to a relatively large range of concentrations. 

Figure 2.6 Detector response curve showing (a) ideal behaviour, (b) real behaviour, (c) its linear range, (d) its dynamic range, (e) the noise level, and (f) the limit of detection at three times the noise level.

Dynamic range (of a detector) The range over which the addition of further analyte brings about an increase, however small, in detector response. 

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