Tektronix 545A Instruction Manual page 12

Operating nstructions — Type 545A
the point where the face of the cathode-ray tube is per ­
manently damaged. If the intensity of the beam is turned
up too far, the phosphor on the face of the crt may be
burned. The intensity of the beam should never be turned
up to the point where a halo forms around the spot.
Graticule llumination Control
The graticule used with the Type 545A Oscilloscope is
accurately marked with 10 horizontal and 4 vertical 1-
centimeter divisions with 2-millimeter markings on the center ­
lines. These graticule markings allow you to make time and
voltage measurements from the oscilloscope screen.
The graticule is illuminated by two lamps located at the
top edge of the graticule. This illumination can be con­
trolled so that the graticule markings appear either red
or white, as desired. The graticule markings are changed
from red to white or from white to red by removing the
graticule cover and rotating the graticule through 180°
about an axis through the center of the graticule (see Figure
As a general rule, white graticule markings are
2-2).
superior to red for photographic purposes.
Fig. 2-2. Rotating the graticule to change the color of the graticule
markings from red to white or from white to red.
Graticule illumination is adjusted by the
control located just under the oscilloscope screen. Rotating
the control clockwise increases the brightness of the grati ­
cule markings and rotating the control counterclockwise
decreases the brightness. For convenience in photographic
work, the CALE ILLUM control is marked in approximate
f-stops. These f-stops can be used with a shutter speed of 1
second when TRI X film is used or with a shutter speed of
10 seconds when Type 44 Polaroid film is used. Regardless
of the type of film used, white graticule markings should
be used. To obtain satisfactory waveform photographs, the
intensity of the trace must approximately match the bright ­
ness of the graticule markings.
2-2
Positioning Controls
Three controls are used with the Type 545A Oscilloscope
to allow you to position the trace to the desired point on
the oscilloscope screen. Two of these controls are used to
set the horizontal position of the trace and are located on
the front panel of the instrument. The third control is used
to set the vertical position of the trace and is located on
the front panel of the plug-in unit used with the oscillo ­
scope. (The Type 53/54C and Type CA Dual-Trace Plug-In
Units have two Vertical Positioning controls.)
The two HORIZONTAL PO ITION controls cause the trace
to move to the right when they are rotated in the clockwise
direction and to the left when they are rotated counter ­
clockwise. The combination of the two controls has a total
positioning range of approximately 12 centimeters with the
sweep magnifier off or approximately 60 centimeters with the
sweep magnifier on. The black HORIZONTAL PO ITION
control has approximately three times the range of the red
VERNIER control.
VERNIER control makes this control particularly useful when ­
ever fine horizontal positioning is required, as for example,
when the sweep magnifier is used.
The vertical positioning control has sufficient range to
allow the trace to be positioned completely off the top
or bottom of the screen or to any intermediate point. The
trace moves up when the control is rotated clockwise and
down when the control is rotated counterclockwise.
Beam Position ndicators
Four small indicator lights located just above the oscil ­
loscope screen indicate the position of the spot or trace.
When one of these lamps is lit, it indicates that the trace
is off-centered in the direction of the arrow. These four
lights allow you to position the spot to the center of the
screen even though the intensity is so low that the trace is
not visible. When the sweep is running, the spot moves
from the left side of the screen to the right and may cause
both horizontal lamps to light each time the sweep runs.
nput Signal Connections
The electrical waveform to be observed is applied to
one of the plug-in unit input connectors. The waveform is
then connected through the vertical-deflection system of the
plug-in unit and the oscilloscope to cause the spot to be
deflected vertically and to trace out the waveform on the
screen of the crt. The vertical size of the displayed wave ­
form is adjusted with the plug-in unit VOLT /CM switch.
CALE ILLUM
The VOLT /CM switch is an accurately calibrated control
which, when used with the graticule, allows you to make
precise voltage measurements from the displayed wave ­
forms. The operation of other plug-in unit controls varies
between plug-in units. For information regarding the opera ­
tion of these controls, refer to the instruction manual for the
plug-in unit you are using.
Certain precautions must be taken when you are connect ­
ing the oscilloscope to the input signal source to insure
that accurate information is obtained from the oscilloscope
display. This is particularly true when you are observing
low-level signals or waveforms containing high- or extremely
The fine range of adjustment of the