Detector impulse response

A transfer function, defined as the Laplace transfer of the impulse response of a linear system, can be obtained from the model. This can be very useful, because with a transfer function the influence of extra-column effects (detector, amplifier, filter) on the peak shape can be easily calculated. The transfer function is ... 

For process control applications, FIA offers the benefit of real-time continuous monitoring by regularly aspirating sample solution (e.g., from a batch-type chemical reactor) into a carrier-wash solution, the detector of choice being operated in an impulse response mode. Thus a chemically modulated signal, continuously recorded as a series of peaks (injected material on a constant background of carrier-wash), offers a positive... 

Neglecting mixing phenomena, the impulse response of the detector is described by a rectangular function of the width, and variance, Aa ... 

In the second case, we try to determine the flow rate of the leak. An injection of tracer is realized in the primary circuit and the impulse responses are measured downstream to both circuits. If the leak exists, some of the tracer will p>ass into the lower pressure stream. There it will be detected either by sampling the process fluid downstream or by monitoring the movement of the tracer using detectors mounted externally. The equation of balance of the tracer allows easily to calculate the flow rate of leak. Leaks so low as 0.1 % can be measured with online external detection, while sampling can identify leaks as small as 0.01% of the main fluid flow rate. 

Time-resolved fluorometry fahs into one of two categories, depending on how the fluorescence emission response is measured (1) pulse fluorometry, in which the sample is illuminated with an intense brief pulse of light and the intensity of the resulting fluorescence emission is measured as a function of time with a fast detector system, or (2) phase fluorometry, in which a continuous-wave laser illuminates the sample, and the fluorescence emission response is monitored for impulse and frequency response. ... 

By introducing a controlled charge and discharge time, a quasipeak detector is achieved. The charge and discharge times may be selected, for example, to simulate the ear s sensitivity to impulsive peaks. International standards define these response times and set requirements for reading accuracy on pulses and sine wave bursts of various durations. The gain of a quasipeak detector is normally calibrated so that it reads the same as an RMS detector for sine waves. 

Figure 14. The response for an electrical impulse into the reaction chamber of an isothermal microcalorimeter of 50 nW. The analysis of this result provides a basis for a performance certification of the instrument. In this case for an instrument set up at 25 C, fitted with a nano Watt detector, the overall noise level for raw data is 3.17 nW, and 12.2 nW over 24 h. The time response of the reaction chamber was found to be 97 sec.

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