Output signal traces

Figure 6. Typical viscometer Output Signal Traces. (Diffepential-ppessupe Capillapy Viscometep)...

Figure 3.35. Dual pass technique used to collect signals due to force gradients 5-50 nm above the surface (A). The resulting output signal traces are shown in (B). Note that the phase or frequency may have a direction owing to the sign of the interaction (e.g., whether positive or negative bias is used in EFM).

Concentration Units. Any discussion of aircraft measurements must begin with a review of various ways in which abundances of trace atmospheric constituents are specified. Such nomenclature is frequently a point of some confusion. In addition, because instruments used on aircraft are operated over a range of pressures, the fundamental way that an instrument senses a species and generates an output signal that is then converted to a measure of abundance is an important issue. The latter concern is discussed in the next section. 

A real-time display helps the operator to monitor the data for consistency between indents and for any systematic trend that arises, for example, from a change in the effective geometry of the indenter, if traces of material from the specimen become transferred to it. The most common reason for an inconsistent set of data is a vibration transient, the effect of which is visible at the time. A subjective decision can then be made to discard that particular data set. Rather than use a real-time display for this purpose, a more reliable approach is to use the output signal from a stylus vibration monitor (a simple modification of the detection system itself) to abort any individual test during which the vibration exceeds a certain level. 

The only important signal trace to consider is usually the feedback trace. If this trace picks up noise (capacitively or inductively), it can lead to slightly offset output voltages — and in extreme cases (though rare), even instability or device failure. We need to keep the feedback trace short if possible so as to minimize pickup and keep it away from noise or field sources (the switch, diode, and inductor). We should never pass this trace under the inductor, or under the switch or diode (even if on opposite... 

The PMT output signal is proportional to the scattered radiation intensity. Becau.se the dispersed particles are in continuous thermal motion, the observed scattered intcn.sity f(i) fluctuates with time. 1 he intcnsity-versus-tinie trace resembles a noise pattern as shown in l-igure 34-ha. Small particles ettuse the in-lensiiy to fluctuate more rapidly than huge pariieles. 

Increasing the detector sensitivity by 2 will result in 2 time peak height, however, noise increases only by s/2 = 1.4 (see Fig. 38-1), the signal-to-noise ratio increases. Note This is only effective with a 10 mV output signal. It has been shown that a 10 mV output has general advantages for trace analysis. 

The output signal of the PD/PM can be fed into a transient recorder, which can record and store traces with a resolution of 1 nsec per channel or slower. Because the changes in intensity are usually small with respect to the total intensity, it is desirable to apply an electronic offset which compensates for the steady-state intensity level. In this way the dynamic range is enlarged. Recorders are available that have a built-in compensation possibility. 

Online detection is an integral part of a gas chromatograph. The detector monitors the column effluent and produces an electric signal that is proportional to the amount of analyte being eluted. The output signal is recorded as a continuous trace of signal intensity against time. In principle, any physical or physicochemical property of the analyte that deviates from the properties of the carrier gas can serve as the basis for detection. Thus, over 100 detectors for GC have been described but relatively few are in common use. 

Figure 9.15. System performance of switch-operated signal-from-noise extractor. Upper trace input signal, 0.5 V/cm. Middle trace output signal, 2V/cm. Bottom trace signals shown above added (using Tektronix type 564 oscilloscope with two-channel preamplifier). The switching circuitry does not distort the pulses. Pulse duration 1 msec.

At the end of this loop, all operators have been scheduled, and the ouQ)ut consists of a set of vectors of feasible optimal arrival times for the output signals from the entire design. The configurations used to create each of these vectors can be recreated by tracing back through the parents of any ouQ)ut vector and noting the configuration used to create each parent... 

Fig. 21. Raman spectra showing improvement of signal-to-noise using multiple scans with computer time averaging over single scan. Lower traces single scan upper traces multiple scans (10 scans) and computer output, (a) i of CCU (b) Hg emission line and n of LiCh (c) n of Na02 with oxygen isotopic counterparts (89).

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