Model 175A Section 111
Paragraphs 3-1 to 3-28
SECTION 111
OPERATION
3-1. GENERAL. (PRESET) at its counterclockwise extreme. The
PRESET triggering condition is best for nearly all
3-2. The front panel labeling of the Model 175A
closely describes the function of each control. The triggered functions. At some discrete frequencies
instrument has a rise time of less than 7 nanoseconds, it may be desirable to move the control out of PRE-
and compatible test probes are provided. Vertical SET.
controls are on the panel of the vertical plug-in unit. 3-17. SWEEP CONTROLS.
Their operation is described in the manual for that
instrument. 3-18. SWEEP TIME.
3-3. BEAM FINDER. 3-19. There are 24 positions of the SWEEP TIME
control, from 5 SEC/CM to 0.1 VSEC/CM, accurate
3-4. BEAM FINDER locates the trace when it might to *3%. Intermediate (uncalibrated) sweep times
otherwise be off the screen. Depressing this button may be obtained by adjusting sweep time VERNIER.
brings the trace on the screen, defocused and intensi-
fied. The POSITION controls can then be adjusted to 3-20. SWEEP MAGNIFIER.
bring the trace to the center of the screen. 3-21. In the INT SWEEP X1 position of HORIZON-
3-5. CALIBRATION. TAL DISPLAY the basic sweep time is that indicated
by the setting of the SWEEP TIME switch. In the XI0
3-6. The CALIBRATOR amplitude is accurate to magnified position the displayed sweep is 10 times
1% from 15°C to 35°C (50°F to 95°F). Square-wave faster, accurate to *5%. Divide the SWEEP TIME
outputs are provided at an amplitude of 1 and 10 volts scale by 10 to obtain the actual sweep time. The
and a frequency of approximately 1 kc. magnified signal is actually 10 screen diameters
across; however, HORIZONTAL POSITION has enough
3-7. TRIGGERING. range to permit any portion of the presentation to be
positioned on screen.
3-8. Four front-panel controls affect the start of the
normal sweep. They are the TRIGGER SOURCE 3-22. On the fastest sweep time, 0.1 FSEC/CM X10
switch, TRIGGER LEVEL control, TRIGGER SLOPE (10 nsec/cm) do not use the first 5 cm of trace for
switch, and SWEEP MODE control.
time-scale measurements since small non-linearities
3-9. TRIGGER SOURCE. may exist. Due to the delayinthe vertical amplifier,
this portion of the trace precedes the actual triggering
3-10. The TRIGGER SOURCE switch selects the point of the waveform. As long as the first 5 cm of
source of the sweep trigger: the power line (LINE), trace is positioned off screen in the 10 pSEC/CM X10
the signal applied to the vertical amplifier (INT), or position of SWEEP TIME, the full 10-cm display may
an external signal applied to TRIG INPUT (EXT AC be used.
or EXT DC). With INT or EXT AC triggering se-
lected, the trigger signal is ac-coupled to the sweep
generator. With EXT DC selected, the trigger sig- 3-23. HORIZONTAL FUNCTIONS.
nal is dc-coupled to the sweep generator.
3-24. HORIZONTAL DISPLAY performs three ex-
ternal horizontal input functions: it selects external
3-11. TRIGGER LEVEL. input, sets the sensitivity to 0.1 v/cm or 1 v/cm, and
3-12. The TRIGGER LEVEL control selects the volt- arranges the input circuit for ac or dc coupling.
age level on the trigger signal at which the sweep
starts. The control provides continuous adjustment
of the trigger level from about -5 volts to about +5 3-25. INTENSITY MODULATION.
volts on external trigger signals and over a range
equivalent to 6 centimeters of vertical deflection on 3-26. INTENSITY MODULATION controls are on the
internal trigger signals. rear panel of the Model 175A (see figure 3-5). A pos-
itive 20-volt pulse will blank the trace at normal
intensities.
3-13. TRIGGER SLOPE.
3-14. TRIGGER SLOPE determines whether the sweep 3-27. STEP-BY-STEP PROCEDURES.
starts on the positive-slope or negative-slope portion 3-28. Figure 3-1 briefly describes the function of
of the trigger signal. each of the Model 175A controls. Step-by-step pro-
3-15. SWEEP MODE. cedures for a few basic operations are given in fig-
ures 3-2 through 3-5. Included are instructions for
3-16. The SWEEP MODE control determines whether compensating the probes. The numbers on each con-
the sweep requires a trigger or free runs. The con- trol refer to the corresponding step in the text below
trol is continuously adjustable with a switchedposition the illustration.
0 1526-1 3- 1 |
ACEC
