Current Root mean square

Similarly, for a current I(t) = I0 cos(ojf), the root-mean-square current /rms is defined by... 

Here we have used AI = 2 x Iac, as defined earlier in Figure 2-2. Once r is set by the designer (at maximum load current and worst-case input), almost everything else is pre-ordained — like the currents in the input and output capacitors, the RMS (root mean square) current in the switch, and so on. Therefore, the choice of r affects component selection and cost, and it must be understood clearly, and picked carefully. 

The power dissipated in an AC circuit with current of maximum amplitude flowing through a resistance is less than the power produced by a constant DC current of magnitude flow ing through the same resistance. For a sinusoidal AC current, the root mean square (rms) value of current I is the magnitude of the DC current producing the same power as the AC current with maximum amplitude I. The rms value I is given by... 

Convergence may be monitored by forming the root-mean-square error of the current estimate as... 

VAR (var). A unit of reactive power. The. reactive power at the por t of entry of a single-phase two-wire circuit when the product of (a) the rms (root mean square) value in amperes of the sinusoidal current, (b) the rms value in volts of the voltage, and (c) the sine of the angular phase difference by which the voltage leads the current is equal to J. (The SI llnil of reacLive power.)... 

The root mean square (r.m.s.) noise voltage AFj for unit bandwidth is A/j/ Y, where A/j is the r.m.s. noise current for unit bandwidth and Y is the admittance. Therefore... 

Table 8.1. Surface properties of the etched ZnO Al films shown in Fig. 8.8. Root mean square roughness (ArrrlK), haze at a wavelength of 700 nm, and resulting short circuit current density, when applied in 1.1pm thick pc-Si I1 solar cells...

Statistical methods are the most popular techniques for EN analysis. The potential difference and coupling current signals are monitored with time. The signals are then treated as statistical fluctuations about a mean level. Amplitudes are calculated as the standard deviations root-mean-square (rms) of the variance according to (for the potential noise)... 

Figures 11 and 12 illustrate the performance of the pR2 compared with several of the currently popular criteria on a specific data set resulting from one of the drug hunting projects at Eli Lilly. This data set has IC50 values for 1289 molecules. There were 2317 descriptors (or covariates) and a multiple linear regression model was used with forward variable selection the linear model was trained on half the data (selected at random) and evaluated on the other (hold-out) half. The root mean squared error of prediction (RMSE) for the test hold-out set is minimized when the model has 21 parameters. Figure 11 shows the model size chosen by several criteria applied to the training set in a forward selection for example, the pR2 chose 22 descriptors, the Bayesian Information Criterion chose 49, Leave One Out cross-validation chose 308, the adjusted R2 chose 435, and the Akaike Information Criterion chose 512 descriptors in the model. Although the pR2 criterion selected considerably fewer descriptors than the other methods, it had the best prediction performance. Also, only pR2 and BIC had better prediction on the test data set than the null model.

Thermal noise — originates from the thermal agitation of charge carriers (- electrons, -> ions, etc.) in a - resistor. It exists even in the absence of current flow and can be described by the formula (/thermal = (4kB TRAf)1/2. [/thermal is the average amplitude of this noise (also denoted [/rms (or Vrms), see also - root mean square), k is the -> Boltzmann constant, R is the resistance, and A/ is the bandwidth of measurement frequencies. 

Flicker noise — is common to all solid-state devices and predominates in measurements at frequencies, / < 300 Hz. Although the physical origin of this noise is not well understood, it can be described by the following empirical equation [/fiicker = (KI2If)1/2, [/flicker is the - root mean square amplitude of this noise, K is a constant depending on factors such as resistor materials and geometry, and I is the DC current [i]. 

For copper, the electrode burn-off versus arcing time has been measured for different short-circuit currents up to 15 kA (root mean square value), see Fig. 6.156. 

Measurement Setup. The buffer capacity measuring setup is shown in Fig. 14. Since the current source is not floating, the grounded counter electrode works as a reference electrode as well. In this case, the current at low frequency will cause a certain polarization in spite of the very large area of the counter electrode. This polarization potential of the counter electrode will be superposed on the output of the ISFET amplifier and interfere with the measurement. Therefore an additional saturated calomel electrode (denoted S.C.E. in Fig. 14) is used to measure separately the polarization potential, and the signal is sent to the lock-in amplifier for subtraction. The measured current and voltage are presented in effective (root-mean-square or RMS) values. 

An electrical measuring instrument contains electrical circuits incorporating capacitance, inductance, and resistance. In the absence of resistance, a circuit tends to oscillate with a definite frequency /when disturbed. For optimum performance an amount of resistance is incorporated that is barely sufficient to damp the oscillations resulting from transient inputs the circuit is then said to be critically damped. For a critically damped circuit it can be shown that the root-mean-square (rms) fluctuations in voltage V and in current /are given by... 

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