Single boxcar integrator

In some instances, the design of the data acquisition system may be driven by the requirements of a specific application. In ICP-MS, for example, the masses of the elemental isotopes are well known, so only those masses need to be investigated. In such a situation, an attractive technique is the use of a number of single-channel devices, such as boxcar integrators [38], each of which is responsible for continually monitoring a specific mass of interest. At the expense of complete mass spectral coverage, a simple, inexpensive system that generates relatively small amounts of data with real-time temporal resolution can be utilized. 

The boxcar integrator is a device which is able to recover the waveform of a repetitive signal or measure the amplitude of a repetitive pulse buried in noise. The major advantage of using a boxcar integrator to measure lifetimes is the relatively low initial cost of the system. The boxcar is basically a sample-and-hold system with two modes of operation, single point and scan, which are used respectively for pulse measurement and waveform retrieval. The time of sampling is determined by a reference pulse that is... 

Fig. 13. Diagram to show the effect of a rising baseline during the recovery of a fluorescence waveform with a boxcar integrator, (a) shows the results with a single scanning aperture and (b) how a second fixed aperture can be used to sample the baseline. The output curve is the difference between the signal in the scanning aperture and that sampling the baseline.

The boxcar integrator needs repetitive waveforms because it samples each time only a small time interval Ar of the input pulse and composes the whole period of the repetitive waveform by adding many sampling points with different delays. For many spectroscopic applications, however, only single-shot... 

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