Magnitude and Phase
Measurements
Velleman Oscilloscope
When measuring the amplitude of a signal, make sure that one of the
cursors located right at ground, verifying this using the readout of one of
the cursor readings.
The phase angle of the signal on Channel 2 using the signal on Channel 1
as the reference is 46.8o using the technique described in Phase Delay.pdf.
Single Frequency Measurements
• Select Waveform Parameters under View on
the upper toolbar of the oscilloscope program.
The magnitudes of the signals on
Channel 1 and Channel 2 are
measured in several different ways make sure that you select the
correct parameter for the type of
measurement requested.
DC Mean – average DC value, which
should be 0V for any periodic wave
centered about 0V and with a 50%
duty cycle.
Peak-to-Peak and Amplitude are the
same for a sine wave– twice the
magnitude of the sine wave. Note
that there are some errors.
Phase angle is one of the
parameters that will be displayed.
You need to determine what the
reference that is being used to
determine the phase angle.
Measurements vs. Frequency
• Select Bode Plotter under Tools on the upper
toolbar of the oscilloscope program.
•
Click on View/Phase Plot.
–
–
The function generator and Channel 2 of the oscilloscope should be
connected to the same points on the circuit.
The voltage and phase of the signal on Channel 1 on the oscilloscope
will plotted with the phase referenced to the signal on Channel 2.
•
Set the desired frequency range and frequency start.
–
–
The function generator and Channel 2 of the oscilloscope should be
connected to the same points on the circuit.
The voltage and phase of the signal on Channel 1 on the oscilloscope
will plotted with the phase referenced to the signal on Channel 2.
• Select a smaller frequency step size to obtain a
more accurate plot of the voltage and phase over
the frequency range.
– The time that it takes to collect this data increases.
The values for the voltage and phase for each data point measured is displayed in the
lower right corner. Or, use the cursors (Markers) to measure the phase and voltage at
specific points on the plot.