Detector Module Functionality

Treffer s model system consists of signal power P (in watts) falling on the input aperture of the modulator (i.e., the spectrophotometer) that modulates the input power as a function of time by a factor M(t) such that 0 < M(t) < 1. The modulation function M(t) is not the modulation of the signal due to chopping but modulation of the signal due to scanning. The modulated signal falls on a detector with responsivity R (in volts per watt) (Kruse et al., 1962 Stewart, 1970) and flat frequency response. The idealized instantaneous... 

Fig. 5) This figure shows a sketch of the investigated detector concept. An irradiated high mobility two-dimensional electron gas device is subjected to a constant magnetic field Bo, where Bo is chosen to correspond to a fixed point (marked as a dot on the top inset) of the resistance oscillations for incident radiation at a frequency f. The detector device function is realized by superimposing on the static magnetic field, a small time varying component, which has been shown here in blue. Then, a high harmonic, tuned band Terahertz sensor is realized by detecting the device resistance at a odd-harmonic multiple of the field modulation frequency, as the detector is illuminated by Terahertz radiation.

The geometric area of each detector module is about 9 by 14 cm about 70% of this area is active. The nominal position resolution of the detector is 1 mm full-width at half maximum (FWHM) at 6 keV (where the response function peaks), and improves with the square root of photon energy. The FOVs of both X- and Y-instruments are approximately 90x90 square degrees, and the overlap between the X- and Y- FOVs is about 90%, The spcctrai resolution is better than 20% FWHM at 6 keV. 

The detector module of a CE system is usually spectroscopic. Hence, its sensitivity is a function of path length, which introduces one of the fundamental problems of linking a flowing separation system to a detector designed for... 

In this discussion only continuous HPLC monitoring or on-line devices will be considered since the discrete methods referred to earlier in the introduction involving sequential analysis of collected eluate fractions are laborious, time consuming and are not therefore used today. An on-line HPLC analyte detector module is defined as a carefully designed device, through which the eluate from the HPLC column flows, and which (in most cases) generates a continuous electrical output signal that is a function of the mass of the analyte or of the concentration of the analyte in the mobile phase. 

Some proportional detectors are combined in the same instrument with a suitable transducer which can perform some of the functions of a controller. For example, for pneumatic systems the primary sensing element actuates a variable air jet, thus modulating an air pressure which is transmitted to a further controller or direct to the controlled device. Electric and electronic detectors such as the infrared detector include the sensing and amplifying circuits of the instrument. 

Mass spectrometers that use electrospray ionization (ESI) do not function well if the eluent contains low volatility salts. This is a major concern when an ion-exchange column is used as a first-dimension column and the salt concentration is used to modulate the retention in this column. In this case, another valve can be connected between the second-dimension column and the detector so that any salt from the second-dimension elution process that is either unretained or weakly retained can be diverted prior to feeding zones to the mass spectrometer. 

For the very small AVj values under consideration the above expression may be linearized, co-AVg. Due to the cosine modulating filter function the NSE instrument measures the cosine transform of S Q,oo). The detector output of the (ideal) NSE instrument at exact symmetry is ... 

Therefore for fixed v and a linearly changing 5, the output of the ideal two-beam interferometer is a cosine function. In other words it is a cosine modulator of the original DC light source. The modulation frequency observed in the AC output of the FTIR spectrometer detector is dependent on the rate at which 5 is increased or decreased, and is given by... 

Operation Qualification. Operation qualification (OQ) is the process of establishing that the instrument or system modules operate according to the functional requirements in a suitable environment. For an HPLC system, operation of the pump, injector, and detector will be tested at this stage. Typical OQ tests for HPLC modules and a UV-Vis spectrophotometer are as follows ... 

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