Horizontal Position Control - Tektronix 7B51 Instruction Manual

Operating Instructions--Type 71351
ABLE TIME/DIV control by pressing in the VARIABLE
knob . This feature is useful when a specific uncalibrated
sweep rate has been obtained and it is desired to switch
between this uncalibrated sweep rate and a calibrated sweep
rate . Switching from uncalibrated to calibrated operation or
vice versa does not affect the setting of the VARIABLE
TIME/DIV control. The VARIABLE TIME/DIV control
allows the sweep rate in each TIME/DIV switch position to
be reduced to at least the sweep rate of the next adjacent
switch position . This provides an overall uncalibrated vari-
able sweep rate range from 50 nanoseconds/division (from
5 nanoseconds/division with MAGNIFIER at X10) to about
12 .5 seconds/division .
When making time measurements from the graticule, the
area between the second and tenth vertical lines of the
graticule provides the most linear time measurement (see
Fig. 2-8) . Therefore, the first and last division of the dis-
play area should not be used when making accurate time
measurements . Position the start of the timing area to the
second vertical line (second line from the left) and adjust
the TIME/DIV switch so the end of the timing area falls
between the second and tenth vertical lines.
Sweep Magnifier
The sweep magnifier expands the sweep ten times. The
center division of the unmagnified display is the portion
visible on the screen in magnified form (see Fig. 2-9) .
Equivalent length of the magnified sweep is more than 100
divisions; any 10-division portion can be viewed by
adjusting the horizontal POSITION control to bring the
desired portion onto the viewing area . The dual-range
feature of the horizontal POSITION control is particularly
useful when the MAGNIFIER is set to X10 (see Horizontal
Position Control discussion which follows) .
To use sweep magnification, first move the portion of
the display which is to be expanded to the center of the
graticule. Then press the X10-MAGNIFIER pushbutton ;
the X10 button lights to indicate that the horizontal sweep
rate is magnified . Whenever the X10-MAGNIFIER push-
button is lighted, the equivalent magnified sweep rate can
be determined by dividing the TIME/DIV switch setting by
10 . For example, if the TIME/DIV switch is set to .05 ps,
the equivalent magnified sweep rate is 5 nanoseconds/
division . The equivalent magnified sweep rate must be used
for all time measurements when the X10-MAGNIFIER
button is lighted . The equivalent magnified sweep rate is
calibrated when the VARIABLE TIME/DIV control is in
the calibrated position .
Horizontal Position Control
The Type 7851 provides both fine and coarse adjust-
ment of positioning . The coarse adjustment provides rapid
horizontal positioning of the trace. Fine positioning is
provided for more precise control of trace position .
2- 1 2
Fig . 2-8 . Area of graticule used for accurate time measurements .
Fig . 2-9 . Operation of sweep magnifier .