Tektronix M 531, Инструкция по эксплуатации

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Operating Instructions— Type M
on the oscilloscope. Set the oscilloscope for external-
triggered sweep operation.
3. Set the MODE switches to AC or DC NORM, depending
on the type of coupling desired.
4. Set the ALTERNATE/CHOPPED switch to the ALTERNATE
or CHOPPED position. In general, the ALTERNATE position
is more suitable for high-frequency signals and the
CHOPPED position is more suitable for low-frequency sig­
nals.
5. Set the VOLTS/CM switches for the desired display am­
plitude. Carefully center the signals vertically using the
POSITION controls.
6. Set the oscilloscope time-base controls (includes the
Variable Time/Cm control) so that one cycle of the ref­
erence signal occupies exactly 9 centimeters horizontally.
Thus, each centimeter represents 40° of one cycle at this
time-base setting (see Fig. 2-6).
Phase Angle = (Channel B, C, or D distance in cm) X ( 4 0 ° )
Fig. 2 -6 . Measurement of phase angles between electrical wave­
forms.
7. Measure the horizontal distance, in centimeters, between
corresponding points on the reference waveform and
each of the other waveforms. Note the distance for each
channel and whether it is leading or lagging. To make
each phase comparison measurement easier, switch the non-
applicable waveforms off by setting the appropriate MODE
switches to the OFF position until you need to display them.
8. For each distance measured, multiply the distance by
40° per centimeter to obtain the phase difference com­
pared to the reference waveform.
For more precise measurements, you can increase the
vertical sensitivity and the sweep rate established in steps
5 and 6, but do not change the setting of the oscilloscope
Variable Time/Cm control. However, when you increase the
sweep rate, you must consider this in your calculations.
For example, if you increase the sweep rate by a factor
of 5, and then measure the distance between waveforms,
each centimeter will represent 8° (40° -t- 5) of a cycle.
By doing this, you can measure phase angles up to 80°
more accurately. When preparing to make the measure­
ment, horizontally position the waveforms to points where
the graticule markings aid in determining the exact dis­
tance. Fig. 2-7, for example, shows how the phase angle
of channel B waveform can be computed using this method.
Other phase-angle measurements can be determined using
the same basic procedure.
Phase Angle = (Channel B distance in cm) X ( 8 ° )
Fig. 2 -7 . Computing the phase angle when the oscilloscope 5X
magnifier is on. Accurate phase-angle measurements within a
range of 8 0 ° can be made using this method.
Time-Delay Measurements
The calibrated sweeps of Tektronix oscilloscopes cause
any horizontal distance on the screen to represent a definite
known interval of time. Using this feature in combination
with the multi-trace feature of the M Unit, you can measure
the time lapse or delay between events displayed on the
oscilloscope screen. This is done by the following method:
1. Follow the procedure outlined in the first five steps
of ‘‘Phase Measurements” .
2. Set the oscilloscope time-base controls for a calibrated
sweep rate which will allow you to accurately measure the
distance between waveforms.
3. Using the graticule, measure the horizontal distance
between the reference waveform and each of the other
waveforms. For most measurements the distance is usually
measured between 50% amplitude points on the rising
portion of the waveforms. To make the measurements be­
tween waveforms easier, switch off the waveforms not
being measured.
4. Multiply the distance measured for each channel by the
setting of the oscilloscope Time/Cm control to obtain the
time interval. (Divide the apparent time interval by the
magnification factor if sweep magnification is used.)
_. ^ . Time/Cm switch setting X Distance in cm
Time Delay = ---------------------- — r-;----------------
Sweep magnification
2-7