Waveform components

The first chapter, Basic electrocardiography, offers an introduction that covers leads, planes, types of ECG recordings and monitoring systems, electrode placement, waveform components, and an 8-step method for interpreting the ECG. This 8-step tool systematically simplifies rather than needlessly complicates the details of ECG interpretation. 

The CamuS system consists of a number of components, both hardware and software, as shown in Figure 1. The hub of the system is the data acquisition unit, which collects and stores ultrasonic data in the form of RF waveforms. An accurate probe position monitor provides information on the location and orientation of the probe as it is scanned over the test object. Software tools have been developed to provide assistance to the user with preparing inspection procedures according to the requirements of prEN1714 with visualising the data, in relation to the test object with making measurements of any indications present and with classifying indications. 

From this it can be seen that vibration is the universal manifestation that something is wrong. Therefore, many units are equipped with instruments that continuously monitor vibration. Numerous new instruments for vibration analysis have become available. Frequency can be accurately determined and compared with computations, and by means of oscilloscopes the waveform and its harmonic components can be analyzed. Such equipment is a great help in diagnosing a source of trouble. 

A power circuit is basically an R-L circuit. In the event of a fault, the system voltage (V , sin ft))) may occur somewhere between V = 0 and V = on its voltage wave. This will cause a shift in the zero axis of the fault current, 7sc> and give rise to a d.c. component. The fault current will generally assume an asymmetrical waveform as illustrated in Figure 13.27. 

These reactances are measured by creating a fault, similar to the method discussed in Section 14.3.6. The only difference now is that the fault is created in any of the phases at an instant, when the applied voltage in that phase is at its peak, i.e. at Vni- so that the d.c. component of the short-circuit current is zero and the waveform is symmetrical about its axis, as shown in Figure 13.19,... 

In an alternating current system the voltage and current components travel in the shape of a sinusoidal waveform (Figure 17.9) and oscillate through their natural zeros, 100 times a second for a 50 Hz system. 

The components connected between the emitter-follower and the currentsensing filter capacitor can be thought of as a resistor divider. An additional 0.17 V needs to appear at pin 7 (through a 1K resistor) so the amount of current that must be contributed to that node is 0.17 V/1K which is 170 pA. The capacitive coupling of the PNP to pin 7 essentially centers the oscillator waveform upon the current ramp. So,... 

Another major source of noise is the loop consisting of the output rectifiers, the output filter capacitor, and the transformer secondary windings. Once again, high-peak valued trapezoidal current waveforms flow between these components. The output Alter capacitor and rectifier also want to be located as physically close to the transformer as possible to minimize the radiated noise. This source also generates common-mode conducted noise mainly on the output lines of the power supply. 

For routine monitoring of machine vibration, however, this approach is not cost effective. The time required to manually isolate each of the frequency components and transient events contained in the waveform is prohibitive. However, time-domain data has a definite use in a total plant predictive maintenance or reliability improvement program. 

The difference between the various pulse voltammetric techniques is the excitation waveform and the current sampling regime. With both normal-pulse and differential-pulse voltammetry, one potential pulse is applied for each drop of mercury when the DME is used. (Both techniques can also be used at solid electrodes.) By controlling the drop time (with a mechanical knocker), the pulse is synchronized with the maximum growth of the mercury drop. At this point, near the end of the drop lifetime, the faradaic current reaches its maximum value, while the contribution of the charging current is minimal (based on the time dependence of the components). 

To improve the selectivity of chronoamperometric in vivo analysis, a differential measurement ta hnique has been employed Instead of a single potential pulse, the potential is alternately pulsed to two different potentials giving rise to the name double chronoamperometry. This waveform is shown in Fig. 15 B. Because the current contributions of individual electroactive components add linearly to produce the observed current output, the difference in current response at the two potentials is the current due to only those compounds which are oxidized at the higher potential and not oxidized at the lower potential. This system provides two responses, the current due to easily oxidized compounds and the current due to harder to oxidize compounds. This gives greater selectivity than the direct chronoamperometric method. 

Figure 2-8 Typical Input Noise and Ripple Waveform of a Buck (AC Component Only)...

As a corollary, the AC component being demanded by the switch/inductor waveform comes entirely from the input capacitors (only). 

However, the entire capacitor current waveform is simply equivalent to taking the switch waveform and translating it down vertically, by an amount exactly equal to the DC value of the switch waveform. Doing so effectively subtracts the DC component from the switch waveform and provides the required AC component to the capacitors. 

The key features of a managed sensor system are that it senses the environment and chooses an appropriate waveform, beam-pattern, pulse repetition interval (PRI), etc (collectively called the sensor mode) to best extract the required information. Any such system must have, at least, the following components in addition to the basic sensor and ancillary components ... 

The factor f reduces the oscillation amplitude symmetrically about R - R0, facilitating straightforward calculation of polymer refractive index from quantities measured directly from the waveform (3,). When r12 is not small, as in the plasma etching of thin polymer films, the first order power series approximation is inadequate. For example, for a plasma/poly(methyl-methacrylate)/silicon system, r12 = -0.196 and r23 = -0.442. The waveform for a uniformly etching film is no longer purely sinusoidal in time but contains other harmonic components. In addition, amplitude reduction through the f factor does not preserve the vertical median R0 making the film refractive index calculation non-trivial. 

The electronic components for the measurements consisted of EG Q Model 173 Potentiostat equipped with slow sweep option (0.1 mv/sec) and EG G Model 376 Logarithmic Current Converter. An EG G Model 175 Universal Programmer supplied the waveform for running the polarization experiment. The output from the electrometer of the 173 and the log output of the 376 were connected to a Hewlett-Packard Model 7036B X-Y Recorder and the potential plotted versus log current. 

This is what the output looks like versus time. The output is not a perfect sine wave and contains some distortion. To see what frequencies the output waveform contains, we would like to create a second plot that displays the Fourier components of the waveform. Select Plot and then Add Plot to Window to add a second plot to the same window. 

We would like the top plot to display the Fourier components and the bottom plot to display the waveform versus time. For a Fourier plot the x-axis is frequency. For a time plot the x-axis is time. Presently both plots use the same x-axis. To allow the plots to have different x-axes, select Plot and then Unsynchronize X Axis ... 

The input and output waveforms are shown on the following left screen capture. Twenty cycles were simulated, but only one is shown in the following left screen capture to make the distortion easily seen. The right screen capture shows the Fourier components of the output voltage waveform. 

Each vendor of SPICE simulation software has added features such as Monte Carlo analysis, schematic entry, and post simulation waveform processing, as well as extensive model libraries. In most cases, the manufacturers have modified the algorithms for controlling convergence and have added new parameters or syntax for component models. As a result, each electronic design automaton (EDA) tool vendor has the basic Berkeley SPICE 2 features and a unique set of capabilities and performance enhancements. 

---