Tektronix 323, Инструкция по эксплуатации

Страница: 32 / 170

Operating Instructions— Type 3 2 3
1. Set the TIME/DIV control to .2 ms and determine the
period time for 1 cycle.
2. Determine how many 0.4 ms divisions it takes to com­
plete 1 cycle, by dividing the period time (from step 1) by
0.4.
3. Using the Horizontal VARIABLE control, set 1 cycle
of calibrator waveform equal to the number of divisions
determined in step 2.
4. A 0.4 ms/div sweep rate has been established. It may
be noted that the ratio of actual-to-indicated sweep rate
(0.4:0.2) exists in all positions of the TIME/DIV control.
VOLTS/DIV: Use the calibration signal to establish a
0.3 volts/div deflection factor.
1. Determine the ratio between the next lower calibrated
deflection factor and the desired deflection factor (0.2/0.3).
Multiply the ratio by 5.
2. Set the VOLTS/DIV switch to 5 DIV CAL.
3. Adjust the VOLTS/DIV VARIABLE control to obtain the
fractional part of 5 divisions which was determined in step
1 (3'/3 divisions).
Lissajous Figures. An unlimited number of trace patterns
(Lissajous figures) can be obtained by simultaneously apply­
ing signals of different frequencies or phase angles to the two
input connectors. If the frequencies are different and do not
have a common divisor, the pattern will change continuously.
If the frequencies are the same, or have a common divisor,
the pattern will be stationary, permitting phase, amplitude
and frequency comparison. (The ease of comparison varies
inversely with the ratio of frequency to common divisor.)
One of the most practical uses of these patterns is in making
extremely accurate adjustments of one frequency in respect
to another.
An analysis of these patterns is a science in itself, and be­
yond the scope of this manual. However, a few patterns
and their interpretations are contained in Fig. 2-15 and 2-16.
v t
1. Center the d isp la y h o rizo n ta lly.
2. M easure to ta l vertical am p litu d e IV t ).
3. M easure am ount o f center vertical line w hich is enclosed
b y ellipse (V c) .
4. D ivide Vc by Vt to o b ta in sine o f phase angle.
5. Determine phase an g le from ta b le o f trigonom etric values.
6. A n g le is > 2 7 0 ° and < 0 9 0 ° i f ellipse rises from le ft
to righ t.
7. A n g le is > 0 9 0 ° and < 2 7 0 ° If ellipse fa lls from le ft
to rig h t.
Fig. 2 -1 6 . D eterm ining phase angle.
—3 dB Point—Half-Power Point
AC Coupling—The condition existing when a capacitor is
inserted between the signal pickoff point and the circuit to
which the signal is applied.
Accelerating Voltage— A voltage applied to components
within a cathode-ray tube to accelerate beam electrons
during their passage from cathode to phosphor screen.
Astigmatism—Any deviation from a circular appearance of
the electron beam spot. Also the control which corrects
for the deviation.
The characteristics of the Oscilloscope’s vertical and hori­
zontal amplifier circuits must be considered in XY opera­
tion. Their bandwidth capabilities determine how much
phase shift each one will introduce. For example, the hori­
zontal circuit will introduce less than 5° phase shift at 10
kHz (its high-frequency half-power point).
The amount of difference in phase shift between the ver­
tical and horizontal circuits will increase as frequency in­
creases. This amount can be determined at any specific
frequency. Couple the same signal into both the vertical
and the horizontal input connectors and calculate the dif­
ference in phase which appears in the presentation, using
the method which is explained in Fig. 2-16.
GLOSSARY OF TERMS
The terms and definitions contained herein are limited to
information required to understand the material in this manu­
al. If a term is synonymous with a preferred term, its def­
inition is restricted to the name of the preferred term.
Attenuator— Normally, any device used to intentionally
decrease the amplitude of a signal prior to its application
to the oscilloscope's amplifier circuitry. Any device which
decreases a signal's amplitude.
Automatic Triggering—Applies to the trigger circuit. A
triggering mode in which triggers to the Type 323 sweep cir­
cuit will initiate triggered sweeps in response to a broad
range of internal or external signals without adjustment
of the triggering level control. It will also provide a free-
running sweep for reference in the absence of triggers.
Balanced Circuit—Two symmetrical (electrically identical)
branches or nodes of a circuit which carry equal but op­
posite polarity signals. Also called Push-Pull circuit.
Bandwidth—The frequency range through which a circuit
will provide an output which is at least 0.707 times the volt­
age output provided at a reference frequency within said
range. The limits are referred to as “ Half Power" or " —3 dB
Points". The lower frequency limit is understood to be DC
if only one value is given.
2-20
®2