How to measure current and voltage with an oscilloscope
For the measurement of DC current or AC current, it is usually done by indirect method. The specific method is:
1, first of all, the current flow will be transformed into a proportional amount of voltage.
2, and then observed with an oscilloscope, the general test method is:
In the circuit under test in series with a high-precision, small resistance value of the non-inductive resistor, and then use an oscilloscope to measure the voltage method, measured the rms value of the voltage across the resistor, and then calculate the value of the measured current, the calculation formula is
I=U/R
Where I-measured current value, A;
U-value of voltage across the resistor, V.
R - the resistance of the series of non-inductive resistance, Ω.
Oscilloscope measurement of DC voltage
Read the vertical distance y between the horizontal bright line and the zero voltage line on the fluorescent screen at this time, multiply y by the vertical sensitivity of the oscilloscope Sy to get the size of the measured voltage ux, i.e., ux=Sy×y.
Measurement of DC voltage with AC component
1, due to the magneto-electric head of the deflection system on the current has an average effect, can not reflect the pure AC quantity, so the DC voltage containing AC components of a common measurement method is to use an analogue voltmeter DC file measurement.
2,If the AC component superimposed on the DC voltage has periodicity and amplitude symmetry, the DC voltage can be measured directly with an analogue voltmeter.
3, by the conversion of AC signals and the DC, such as rectification and filtering of the DC average, as well as non-simple harmonic wave of the average DC component can be measured with an analogue voltmeter.
4, can not use the digital multimeter to measure the DC voltage containing AC components, because the digital DC voltmeter requires the measured DC voltage stability, in order to display the number, otherwise the number will jump non-stop.
