## 3 Procedures for Assessing the Characteristics of the E/A
### The Designation of Characteristics of Measurement Channel  
The proper calibration of the instrument's input circuits seems to be a basic requirement. Probably, for most of the effects described in [15; 16], it can be assigned to the change of the conversion characteristics of the DA section of the devices used in the experiment. Independently, the accuracy of the designation of a particular power quality coefficient also depends on the correctness of the algorithms applied in the DDP part of the measurement channels. The goal of the performed experiments is, most of all, the examination of the algorithms embedded in the software executed in the DSP. The research was carried out using the four basic arrangement configurations presented in Figure 11. The estimation procedures are performed in applications running on a PC. The distinction of the DA and DDP parts in the measurement channel allows one to apply various test signals and calibration techniques for the estimation of the measurement features of the E/A instrument. The experimental layout in Figure 11a figuratively shows the preliminary tests of the E/A instrument algorithms. The software designing, as well as the initial verification of the measurement algorithms implemented in software of the E/A, were carried out using the evaluation board EVAL-TS2015-EZKIT Analog Devices (Analog Devices, Norwood, MA, USA) (Figure 12) [39], equipped with two TigerSHARC processors, the same as the DSP used in the E/A instrument (Figure 2). Figure 11: Experimental setups for the verification of measurement algorithms: (**a**) The preliminary assessment of algorithms in the development kit; (**b**) The estimation of algorithms with the use of pattern analog signals; (**c**) The estimation with the use of the raw samples of signal and coefficients designated in the E/A; and (**d**) The estimation using the reference instrument. Due to the different configurations of the peripheral circuits of the DSP processors on the evaluation board and in the E/A instrument, the verification only included the selected portions of the measurement functions. However, the verification of the algorithms for measuring the individual factors of energy quality has been fully carried out using the standard sets of digital data. These studies were important to start the instrument, in spite of a limited set of test data which cannot cover various measurement conditions. As a result, the software can be embedded in the DSP on the E/A instrument. Figure 11b shows the calibration setup using the standard analog test signals. Just as in the previous layout, the set of testing signals is limited, but the calibration procedure refers to both parts of the channel: the DA and the DDP. As a standard signal source, the 3-phase generator Chroma type 6590 Programmable AC Power Source was used [40]. The same signal source was also used, among others, in the setup shown in Figure 11b,c. In the experimental setup in Figure 11b, the measurement results from the E/A are assessed in a PC-based estimation system, taking into account the features of the test signal from the Chroma generator. Another way of verifying the measurement characteristics of the E/A was achieved using the registered raw samples of the signals. In the experimental setup shown in Figure 11c, for the stationary test signals, the digital representations of the raw samples of these signals were registered. For the same test signals, after changing the option of instrument operation (Figure 5), the particular coefficients are registered. In the estimation arrangement, supported by the PC computer with running software package (independently tested using pattern data), the registered raw samples are processed and then the calculated coefficients are compared with the coefficients obtained from the examined E/A instrument.