Applications
Phase
Difference
Between
Two Signals
1.
Using either probes or cables with equal time delays, display the reference
signal on CH 1 and the comparison signal on CH 2. For higher frequencies,
signal delay matching is more critical. The procedure for matching delays is
found under "Matching Channel 2 Delay" in Section 4.
2.
Set CH
1
and CH 2 VOLTS/DIV and VAR controls to obtain equal
amplitudes of the reference and the comparison signals. Set the amplitudes
as large as is practical.
3. Set Vertical POSiTiON controls to center both displays vertically. Phase
measurement accuracy depends on the accuracy of vertical centering.
4.
Set SEC/DiV and VAR to display one cycle of the reference signal over five
horizontal divisions.
5. Activate 1/At by pressing both the At and AV buttons together.
6. Align the Reference cursor with a zero-crossing of the reference signal.
Align the Delta cursor with the nearest zero-crossing of the comparison
signal,
on the same slope as the reference signal zero-crossing (see Figure
3-6). Use the center horizontal graticule line as the reference for aligning the
zero-crossings.
7. Read phase shift in degrees from the CRT readout.
If the phase shift is less than
1
horizontal division (72 degrees), you can
improve the accuracy of the measurement. Use the X10 MAGnifier, without
changing SEC/DIV or VAR, to expand the display; align the cursors with the zero
crossings; and divide the PHASE readout by 10 (see Figure 3-7).
2465B/2455B/2445B Operators 3-15
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