Beamfinder; Calibrator; Z-Axis Input; Intensity Limiting - Tektronix 7140 Instruction Manual

Operating Instructions-7104
BEAMFINDER
brightness . Notice that after about one minute the red
38 . Set the deflection factor of the left amplifier unit to
SHUTDOWN light starts flashing and then after about 10
10 millivolts/division and the calibrator for a 4 V output .
seconds turns on steady ; at the same time the crt display is
Notice that the square-wave display is not visible, since
turned off. Press the RESET button and the display should
the deflection exceeds the scan area of the crt.
return .
39 . Press the BEAMFINDER pushbutton switch ; notice
that the display is returned to the viewing area in
compressed form . Release the BEAMFINDER switch and
notice that the display again disappears from the viewing
area .
40 . With the BEAMFINDER switch pushed in, increase
the amplifier-unit deflection factor until the display is
reduced to about 2 divisions vertically . Adjust the
position control of the displayed amplifier unit to position
the compressed display near the center of the graticule.
Release the BEAMFINDER switch and observe that the
display remains within the viewing area .
CALIBRATOR
41 . Connect the CALIBRATOR output to both the left and
right vertical units with two bnc cables and a bnc T
connector . The display amplitude should be
approximately 2 divisions. If not, adjust the deflection
factor accordingly .
42 . Select different CALIBRATOR pushbuttons (labeled
4 V, 0.4 V, and 40 mV) and notice that the displayed
signal changes accordingly . (CALIBRATOR output must be
terminated into more than a 100-kilohm load for stated
output .) When the CALIBRATOR output is terminated into
50 ohms, the output is 0.1 times the stated output .
Z-AXIS INPUT
43 . If an external signal is available (+2 volts peak-to-peak
minimum), the function of the Z-AXIS INPUT can be
demonstrated . Connect the external signal to both the
input connector of the displayed amplifier unit and the Z-
AXIS INPUT connector. Set the sweep rate of the
displayed time-base unit to display about 5 cycles of
signal . Set the amplitude of the signal generator until
intensity modulation is visible on the display (change the
amplifier unit deflection factor as necessary to produce
an on-screen display) . The positive peaks of the
waveform should be blanked out and the negative peaks
intensified . Notice that the setting of the intensity
control determines the amount of intensity modulation
that is visible. Disconnect the cables .
INTENSITY LIMITING
Figure 2-3. Definition of graticule measurement lines .
44 . Connect a sinewave signal to the input of the
displayed amplifier unit . Set the amplifier deflection
factor to display 8 divisions of signal . Set the displayed
GRATICULE ILLUMINATION
time-base unit to display at least 20 cycles . Rotate the A
or B INTENSITY control clockwise and observe that the
The GRAT ILLUM control varies the illumination of the
yellow LIMITED VIEWING TIME light turns on and then
graticule lines. The GRAT ILLUM can also be operated in
flashes on and off as the intensity control is rotated
the PULSED mode . With the GRAT ILLUM control set to
further clockwise. With the LIMITED VIEWING TIME light
the PULSED detent position, and the + GATE/EXT switch
flashing, the intensity is limited. Rotating the intensity set to + GATE, the
graticule will be illuminated
control clockwise does
not increase the displayed
momentarily after the + GATE occurs . The + GATE
2- 8
GRATICULE
DETAILED OPERATING
INFORMATION
The graticule is marked on the inside of the crt faceplate,
providing accurate, parallax-free measurements . The
graticule is divided into eight vertical and ten horizontal
divisions. Each divison is a 0.85 centimeter square
divided into five minor divisions along each axis . The
vertical gain and horizontal timing of the plug-in units are
calibrated to the
graticule so that accurate
measurements
can be made from the crt. The
illumination of the graticule lines can be varied with the
GRAT ILLUM control.
Figure 2-3 shows the graticule and defines the various
measurement lines. The terminology defined here will be
used in all discussions involving measurements from the
graticule. The markings : 0%, 10%, 90%, and 100% on the
left side of the graticule are for accurate rise-time
measurements .
SECOND
CENTER TENTH
VERTICAL VERTICAL
VERTICAL
LINE LINE LINE
b
CENTER
HORIZONTAL
LINE
p
1675-7
REV APR 1981