Tektronix 7844, Инструкция по эксплуатации

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When the R EADOUT controls are set for non-pulsed opera­
tion, the beam 2 display is interrupted by the character gene­
rator during the time each character is written. The time
interval, between characters being written, is automatically
varied, thereby reducing the possibil ity that blank spots in
the beam 2 display will be noticeable.
In the R EADOUT PU LSED mode, the readout d isplay is
written by beam 2 at the end of each sweep. For single
sweep applications, the pulsed mode e l i m i nates the beam 2
display interruptions. However, when high speed repetitive
signals are displayed, blank spots on the beam 2 display may
appear.
If the beam 2 display interruptions become objectionable,
the character generator can be disabled by rotating the
R EADOUT INTENSITY control to the O F F position. For
further information on readout operation, refer to the Read­
out Display discussion in this section.
Amplifier Unit Alternate Operation
Dual-trace 7000-series amplifier plug-in units with alternate
display modes can be used with the 7844/R7844. Alterna·
tion occurs after the completion of each sweep when each
amplifier plug-in unit controls only one beam or when both
beams are controlled by the same time-base unit,
However, when the same amplifier unit (set for alternate
operation) is selected for vertical deflection of both beams
and different time-base units are selected for the horizontal
deflection of each beam, a special condition exists in the
oscill oscope logic circuits (this condition exists only in instru­
ments which have V E RTICAL M O D E switches). The B
H O RIZ time base completes one sweep and locks out further
B sweeps until after the next A H O RI Z sweep is completed.
At the end of A HORIZ sweep, alternation occurs within
the amplifier unit and the A H O RI Z and B H O RI Z sweeps
are unlocked for another alterna,te cycle. A H O RIZ sweeps
that end before the end of B H O RI Z sweep have no affect
on alternate operation withi n the amplifier unit.
Therefore, when an amplifier unit controls the vertical de­
flection of both beams, both the A H O RIZ and B HORIZ
compartments must have time-base units installed and each
sweep must be running for proper alternate operation with�
in the amplifier unit. If the A H O RI Z compartment does
not have a time-base unit installed or the time-base sweep is
not running, the B H O RI Z time-base unit will generate one
sweep, then there will be no display. If the B H O RIZ com­
partment does not have a time-base u n i t installed or the
time base sweep is not running, the A H O RIZ time-base unit
wi l l be displayed.
@
Operating Instructions-7844/R7844 O perators
Trigger Sou rce
The Trigger Source switches allow the horizontal plug-in
units to acquire an isolated replica of either the left vertical
or right vertical displayed signals. The Trigger Source swit­
ches are generally used for internal triggering of time-base
units but can be used to route input signals to special pur­
pose pl ug-in un its such as counters,
Intensity Modulation
Intensity (Z-axis) modulation can be used to relate a third
item of electrical phenomena to the vertical (Y-axis) and the
horizontal (X-axis) coordinates without affecting the wave­
shape of the displayed signal. This is accompl ished by
changing the intensity of the displayed waveform to provide
a "gray scale" display.
The voltage amplitude required for visible trace modulation
depends on the setting of the I NTENSITY controls. A 2
volt peak-to-peak signal will completely blank the d isplay
even at maximum intensity l evels; lower amplitude signals
can be used to increase or decrease the trace brightness. A
positive-going signa! will decrease the trace brightness and a
negative-going signal will increase the trace brightness. Re­
fer to Table 2- 1 for signal requirements.
Time markers applied to the Z-AXIS I N PUT provide a d irect
time reference on the display. With uncali brated horizontal
sweep or X-Y mode operation, the time markers provide a
means of reading time directly from the display. If the
markers are not t ime-related to the displayed waveform, use
a single-sweep display.
Remote Grat/Readout Single Shot
The G R AT/READOUT SIN G L E SHOT B N C connector
(l ocated on the rear panel) allows an external signal to ac­
tuate one frame of readout information and one momentary
i l l u m ination of the graticule when the R EADOUT I NTEN­
SITY and G R AT I L LUM controls are set to PULSED, and
the EXT/BEAM 2 GATED push buttons for R EADOUT and
G RAT I L LUM are set to EXT. The signal source can be
either active (pulse generator, logic circuit, etc.) or passive
(switch or relay) . Refer to Table 2- 1 , in the Specification
section, for input requirements.
Single Sweep I nput/Output
The single sweep feature of the 7B-series time-base u nits can
be reset with an external signal appl i ed to the SIN G L E
SWEEP R ESET connector. The signal source can be either
active (pulse generator, !ogic circuit, etc.) or passive (switch
or relay ) . A and B READY outputs are provided for exter­
nal indicators. The indicators signify that the time-base unit
has been reset, and is ready to present a single sweep when
the next trigger pulse arrives. Refer to Table 2- 1 , in the Spe­
cification section, for signal parameters.
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