Tektronix 5110, Instruction Manual

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Operating Instructions—5110
High Resolution Phase Measurement
More accurate dual-trace phase measurements can be
made by increasing the sweep rate (without changing the
variable Seconds/Div control setting). One of the easiest
ways to increase the sweep rate is with theSwp Mag (10X)
button on the time-base unit.
EXAMPLE: If the sweep rate were increased 10 times
with the magnifier, the magnifier sweep rate should be
45° /division 10 = 4.5°/division. Figure 1-9 shows the
same signals as used in Figure 1 -8, but with the Swp Mag
button pushed in. With a horizontal difference of six
divisions the phase difference is:
2. Set each amplifier unit input coupling switch to de,
and set the position controls of the selected X and Y
channels for a spot display at graticule center.
3. Connect low-frequency sine-wave signals of the
same frequency to the selected X and Y inputs.
4. Advance the INTENSITY control until the display is
at the desired viewing level. Set the amplifier deflection
factors and variable Volts/Div controls for six divisions of
vertical and horizontal deflection, and set the position
controls to center the display on the graticule as shown in
Fig.
1-10.
Phase
Difference
horizontal
= difference
(divisions)
X
magnified
sweep rate
(degrees/
= (6) (4.5D)=27°
division)
5. Measure and record the overall vertical deflection
(A) and the opening of the Lissajous display (B), measur­
ing vertically at the graticule horizontal center line (see
Fig. 1-10).
The phase difference is 27°.
Channel 1, or left Channel 2, or
plug-in (reference) center plug-in
6. Divide B by A to obtain the trigonometric sine of the
phase angle difference between the two signals. Obtain
the phase angle from a trigonometric table to determine
the phase angle between the X and Y signals. If the display
appears as a diagonal straight line, the two signals are
either in phase (tilted upper right to lower left), or 180° out
of phase (tilted upper left to lower right). If the display Isa
circle, the signals are 90° out of phase. Fig. 1-11 shows the
Lissajous displays produced between 0° and 360°. Notice
that above 180° phase shift, the resultant display is the
same as at some lower angle.
EXAMPLE: Assume a
display as shown in Fig. 1-10
where A is 6 divisions and B is 0.4 division.
ng. 1-9. High-resolution phase difference measurement with
Increased sweep rate.
X-Y Phase Measurements
The X-Y phase measurement method can also be used
to measure the phase difference between two signals of
the same frequency. The phase angle is determined from
the Lissajous pattern as outlined in the following steps:
1. Insert an amplifier plug-in unit into one of the
vertical plug-in compartments and an amplifier of the
same type into the horizontal plug-in compartment. Fig. 1-10. Phase difference measurement from an X-Y display.
1-14