Signal acquisition speed

Despite these strengths, ICP-MS has also some important drawbacks, many of them related to the spectral isotopic and/or chemical interferences, which affect analyte signal intensities and, therefore, the applicability of the technique. The complexity of the optimisation of the methodological and operating conditions, the differences in the ionisation rates of the various elements, the sequential isotopic measurements and the limited speed of signal acquisition (a serious drawback in multielemental analysis of fast transient signals) are some other problems to be considered. 

One of the main problems in fast signal acquisition is development of a suitable active photomultiplier (PM) base. An anode risetime of no more than 20 nsec is desirable and the ability to drive 50-ohm cable with a steady DC voltage of 1.0 V is also important. However, the maximum anode DC current that most PMs can handle is about 100 pA. All these facts translate into the need for an active PM base, that is, a base that has a high-speed amplifier driving the cable. In our experiments we have the added requirement of gating the PM off for sub-microsecond times to do the phosphorescence experiments mentioned briefly in this paper. Can all these features be put into one unit Yes. 

Accurate signal sampling reportedly requires using a data acquisition speed at least double —although, preferably ten times— Nyqulst s frequency viz. the minimum sampling frequency). Figure 2.4 Illustrates how a given sam-... 

It is therefore obvious that computerized data acquisition Involves a number of essential factors such as the length of the experiment, the magnitude and frequency of the generated signals, the speed of data acquisition and the nature of the measuring Instrument, all of which have been given due consideration In the literature [3,8-11] and In reports on the use of digital... 

The detector signal from a separations experiment, when plotted vs. time, yields a series of (ideally) Gaussian peaks, each repaesenting one compound in the sample. Acquisition speed... 

For the AE system, a high-speed signal acquisition should be used to monitor the lapping process in real time. Many experiments on work parameters and the quality of lapped workpieces should be carried out to confirm the conclusions drawn so far. Based on the experimental results, a practical database can be established and used in real production. Some new programs should be developed to efficiently analyze AE signals and correlate them to surface integrity. 

For process control, analytical techniques such as vibrational spectroscopies, which provide information about paint composition, are important based on (1) the popularization of FT instruments, with a better signal-to-noise ratio and fast data acquisition speed (2) reflectance techniques (total attenuated and diffuse), photoacoustic spectroscopy, and the development of optical fiber-based devices that provide easy spectrometric measurements on crude samples (3) vapor-phase generation coupled with FTIR for fast analysis of the volatile paint fractions ... 

Unfortunately, the actual depth resolution can deteriorate a bit as a result of different effects, such as pulse mixing and signal taihng induced during aerosol transport, and will ultimately depend on the flow characteristics of the ablation cell and the data acquisition speed of the ICPMS unit used [25,45]. Moreover, the ratio between the depth penetration and the laser beam diameter must be kept below a critical value in order to obtain representative in-depth compositional data [43,46] thus, the use of larger beam diameters yields reliable information from deeper in the sample. 

A series of such measurements has been performed on the journal bearing for a range of speeds and loads. The output is an array of film thickness values for each measurement frequency (similar to that shown in Figure 9). Software written in Labview control the signal acquisition and processing so that film thickness results are presented automatically. Figure 10 shows the measured film thickness results. 

Pulses of ions can be directed into the TOF analyzer at the rate of about 30 kHz, and, therefore, more than 30,000 spectra per second can be collected and summed. There are significant improvements in signal-to-noise ratios and speed of acquisition of data. 

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