Design of Conducted Disturbance Test Based on EUT Equipment

The high frequency current probe is mainly aimed at the measurement of floating system. In power system testing, it is often required to measure the relative voltage difference between the live wire and the live wire, or the live wire and the zero (center) wire in the three-phase power supply. Many users directly use a single-ended probe to measure the voltage at two points, causing the probe to burn out from time to time. Using a special power supply module, the high-frequency current probe has higher stability and lower noise. Its LVC high series of high frequency current probes use extremely low temperature coefficient and voltage coefficient for internal components, which can provide extremely high testing. All active high-frequency current probes have an output impedance of 50Ω, which can be applied to all oscilloscopes and voltmeters.
Analysis of the process and characteristics of the two measurement methods of high-frequency current probes. Users can enter the test mode to adjust the offset voltage. If the high-frequency current probe is out of adjustment after long-term use, the user can enter this mode to adjust the offset to achieve zero ;Electronic light-touch buttons make the service life longer.
1. Use two high-frequency current probes to measure, and then use the math function of the oscilloscope to calculate: Use two high-frequency current probes to make two single-ended measurements. This is a common method and an undesirable method for differential measurement. Measure the signal to the ground (single-ended) and use the math function of the oscilloscope (channel A signal minus channel B) to measure the differential signal. When the signal is a low-frequency signal, and the signal amplitude is large enough to exceed any worry about noise, this method can be adopted. The combination of two single-ended measurements has multiple potential problems. One of the problems is that there are two separate long signal paths along each probe until each oscilloscope channel. Any delay difference between the two paths will cause the two signals to shift in time.
2. Oscilloscope floating measurement: The current common false floating measurement method is the oscilloscope floating measurement method, which is to cut off the connection between the neutral wire and the ground wire by cutting off the ground wire of a standard three-head AC socket or using an AC isolation transformer. This method is actually not feasible, because the neutral line may have been connected to the ground line in the wiring of the building, which is an unsafe measurement method; in addition, it violates the industrial health and safety regulations, and the measurement results obtained are also difference. In addition, a large parasitic capacitance will appear when the oscilloscope is floating on the ground, and the floating measurement will be damaged by the oscillation, and the measured waveform will be severely distorted. An example will be demonstrated later.