## 3 Test Stand  
Electromagnetic emission testing requires an appropriate procedure and professional measurement equipment. The tests consist of two parts. The first part is the analysis of radiated interference emitted by the reactor installation, and the second part analyses the conducted interference measured in the power supply and ignition system of the reactor. The measurement of radiated disturbances requires that the equipment under test is located in a separate area free from external interference during measurements. The measurements were taken in March 2020, when the university was closed due to an epidemiological emergency (coronavirus COVID-19). This reduced the external interference because all laboratories in the building were shut down. There were no additional disturbances in the background. Radiation interference from the plasma reactor was investigated at a distance of 3 m from the installation. The 30 MHz-3 GHz frequency band was analysed. Legal requirements define the band only up to 1 GHz, but the band was increased to 3 GHz. This is because when the reactor is working, the Wi-Fi is not working properly. The measuring system consisted of an interference meter and three measuring antennas. An interference meter is a measuring interference receiver (EMI test receiver). It uses model ESCI3 (Rohde&Schwarz GmbH & Co KG, Munich, Germany), which is compliant with standard CISPR 16 (Comite International Special des Perturbations Radioelectriques) [29]. The EMI test receiver is an indispensable apparatus in quantifying the magnitude of radio and conducted interferences emitted from that installation. That meter is also used to determine apertures compliant with national and international EMC standards. Antennas are used for measurements: HK116 Biconical Antenna (30-300 MHz), HL223 Log-Periodic Antenna (0.3-1 GHz) and HF906 Double-Ridged Waveguide Horn Antenna (1-3 GHz), all antennas are products of the Rohde&Schwarz GmbH & Co KG, Munich, Germany. These broadband antennas are used to measure radiated electromagnetic fields with an error of not more than \(\pm\)3 dB. The measurement method and structure of the measuring station itself are based on the CISPR 16 [30] standard and the idea is presented in Figure 3. Sampling ranges have been set according to the standard. The tests have been done for two antenna polarisations--horizontal and vertical. The second part of the tests concerns the measurement of conducted disturbances. The reactor installation does not have electronic control or data systems, so the tests of conducted electromagnetic interference are limited to the analysis of the power supply circuits. The elimination of additional (control) devices is a good idea here. This is the author's new approach. It is related to the fact that the additional devices introduce some couplings and change the propagation of interference in the installation. The reactor has two circuits; the operating circuit and the ignition circuit, so two measuring systems are used. Conducted disturbances were measured in the circuit of the reactor, ranging from 150 kHz to 30 MHz. The main elements of the measurement system are the EMI receiver and a special additional device--LISN (Line Impedance Stabilisation Network), working as an artificial network. Figure 4 shows the measuring system. An ESCI3 Rohde-Schwarz was used in all tests as an EMI receiver. A line impedance stabilisation network (LISN) is a device used in the conducted radio-frequency emission, as specified in various electromagnetic compatibility (EMC)/EMI test standards. A LISN is used to measure conducted emissions on power lines. It draws power from the ordinary wall outlet and feeds this to the equipment under test (reactor installations). Any disturbances generated by the reactor are separated by the LISN and fed to the EMI receiver for measurement. In the power circuit of the working electrodes a three-phase LISN (model SMZ-6/50, INCO Warszawa, Poland) was used.