## 3 Results  
The front panel of the application consists in indicators and controls, representing no correction condition [18; 19; 20], as shown in Figure 6. Even if the difference with respect to the value of the active power without applying a correction was around 1 W (for the considered load), on a large scale, this component had an influence, becoming significant. The experimental results were for different sampling frequencies. The reported errors were calculated by relating the uncorrected values to the corrected ones. The quantities for which they were calculated were the sampling frequency, the active power, the apparent power, and the reactive power. The measurements were made for different loads of 1.5, 2, 2.5, and 3 amperes. The load used was of the R-L type (resistance-inductance). There was an inductive phase shift in the circuit of approximately 11-12 degrees (a coiled resistor was used). Figures 7 and 8 show the case of errors (vs. sampling frequency, fs) affecting the active power measurement. The errors were computed according to Equation (12). Pmeas is the measured active power, and Pcorr is the corrected active power. Similarly, the apparent power and reactive power errors are outlined. For stability reasons, the measurements were made using the average of ten values for each power. \[\varepsilon=(\mathrm{P_{meas}}-\mathrm{P_{corr}})/\mathrm{P_{corr}}\cdot 100 \ [\%] \tag{12}\]  
Figure 6: Front panel of the application. The small error differences in the case of active power (P) were due to the use of an appropriate sampling frequency. But even when the sampling frequency was adequate, a sampling error existed. A special behavior of the active power was observed at low sampling frequencies. Low sampling frequencies allowed the acquisition board to be more effective (error decrease) in terms of synchronization. The samples were better synchronized, and the acquisition process was more stable than at high sampling frequencies. The apparent power S had a different shape at all loads (1.5, 2, 2.5, and 3 A) and showed the same behavior. For the apparent power, the errors were practically the same because the RMS values were the same, theoretically, regardless of the sampling frequency. The differences that appeared between the values with or without correction were due to changes in the amplitude of the signals due to the applied interpolation/extrapolation. The error increased significantly at low sampling frequencies, as shown in Figures 9 and 10. Without using this correction, the errors became significant in some conditions. Figure 8: Active power measurement error, current correction. Figure 7: Active power measurement error, voltage correction. The errors increased with a decrease in the current, because at low currents, non-linearity errors of the measuring chain components also appeared. We must remember that the acquisition board was chosen with low performance specifically to highlight this error. It is obvious that for acquisition boards with higher performance (higher sampling frequency or lower number of channels), the sampling error is lower. The last power analyzed was the reactive power, Q, at the same loads (resistive-inductive), as shown in Figures 11 and 12. Because of the load applied, with a small reactive component consisting of a shift phase of around 10 degrees, the error was much higher than those previously determined for the other electric power types (active and apparent). The results are very close (seems to be identical, but they are slightly different). If the load had a strong reactive character, the errors would have been inversely proportional, i.e., higher for the active power and lower for the reactive power. Figure 10: Apparent power measurement error, current correction. Figure 9: Apparent power measurement error, voltage correction.