This test load will later allow me accurate and repeatable measurements on a Vector Network Analyzer for comparison. Fixture used to take complex loads measurements.įorm my example #1, I prepared a SMA male connector with soldered a 33Ω SMD resistor in parallel with a 330pF SMD capacitor. The central pins are soldered together, while the ground flanges are connected by mean of a 12Ω resistor, which is my known “R”. To easen the measurements I prepared a simple fixture made of two SMA female panel connectors soldered back to back.
Thus, the phase difference between CH1 and CH2 gives the φ between voltage and current. This measurement gives us the current I along the entire circuit (I = V2/R). Instead we measure I1 by adding a known resistor R in series with Z and measuring the voltage drop across it with the CH2 probe. We measure V1 by simply connecting the CH1 probe across the load. the phase difference between voltage and current.Īs we know, an oscilloscope can measure voltage, but how can it measure current? The answer is very simple, use one of these configurations: Beside the magnitude of V1 and I1, we need also to know φ, i.e. The only difference between these measurements and those made at DC is that here all involved values are complex numbers. The measurement of an unknown load, and the power that is being delivered to it, is conceptually very simple thanks to the Ohm’s law: A very interesting one, at least for educational purposes, is the measurement of complex loads: R, X, VSWR, Return Loss, Phase, capacitance, inductance and real power. The oscilloscope is a very powerful tool that has many functions.
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