Operating Instructions-7844/R7844 Operators
condition specified for
X-
Y displays. The 7 S 1 4 has
X-
Y
operation incorporated as one of its norma! mode functions.
Special Purpose Plug- I n Units
The variety of special-pu rpose plug-in units available al lows
the 7844/R7844 Oscil loscope to be used for many specializ
ed applications, The fol l owing is a brief discussion of some
of the available special-purpose plug-in units.
DIGITAL COUNTERS AND MULTIMETER PLUG-IN
UNiTS.
The digital multi meter plug-in units measure cur
rent, voltage, temperature, and resistance; digital frequency
counter plug-in units measure frequency, from de to above
500 MHz. These units make use of the readout system to
display the measured information on the crt and can func
tion in any compartment, in combination with each other
or with any other plug·in units available for use with the
7844/R7844 oscil loscope system.
The ability of digital readout plug-in units to operate with
other plug-in units makes it possible to process and monitor
signals at the same time the digital measurement is being
made. For example, by locating a frequency counter in one
of the vertical compartments and an amplifier unit in the
other vertical compartment, the crt can display the trigger
waveform, superimposed on the displayed signal, to indicate
the actual triggering point, Or, if the counter is placed in a
horizontal compartment, a low-amplitude signal can be
applied to a vertical ampl ifier and amplified before it is in
ternally routed, by the trigger source switches to the counter
trigger circuit. This allows the u n i t to be used on signals too
small to trigger other counters.
READOUT ACCESS PLUG·IN UNIT.
The 7 M 1 3 R EAD·
OUT plug-in unit provides front-panel keyboard operation
for convenient access to the crt readout characters, Th is
allows information, such as dates and identifying nomencla
ture, to be displayed on the crt with the normal crt display.
This capability is particularly useful when making photo
graphs.
TRANSISTOR CURVE·TRACER PLUG·IN UNITS.
The
7000-series transistor curve-tracer plug-in units check smal l
signal transistors and diodes by producing a display showing
the basic characteristic curves for the device being tested.
Stepped sweep signals from an internal power supply are
applied to the device under test. The resulting output sig
nals are, in turn, applied to the horizontal and vertical de
flection systems of the oscilloscope to plot a family of
characteristic curves. This plot can be used to check for
damaged transistors and diodes, or to select for special or
matched characteristics, and to calculate gai n , leakage, break
down voltage, etc.
1-18
SPECTRUM ANALYZER PLUG·IN UNITS.
The 7000·
series spectrum analyzer plug-in units display applied signal
amplitude dispersed over portions of the rf spectrum. Ab
solute signal energy is plotted on the vertical axis against
frequency on the horizontal axis. Applications include
waveform and distortion analysis, emi and random noise
measurement, filter design, spectrum surve i l l ance, etc.
D I R ECT ACCESS UNIT.
This plug·in unit provides ac
coupling of high-frequency or fast-risetime signals directly
to the crt vertical deflection plates. Two front-panel input
connectors permit either single ended or differential opera
tion (internally selected) . Trace positioning is accomplished
with a front-panel control. Di rect access units can be in
stalled in either or both vertical compartments. However,
the readout capabil i ty for the 7844/R7844 is lost when in
stalled in the right vertical compartment. Also, the
V E R
T
I
CA L M O D E switch is inoperative on the standard 78441
R 7 844 when the di rect access u n i t is installed in either
vertical compartment. When one di rect access unit is instal
led in either compartment the other compartment can be
used for normal plug-in functions. Refer to the direct
access u n·lt instruction manual for installation information.
X-V Operation
In some appi'lcafions, it is desirable to display one signal
versus another (x-y) rather than against time ( i n ternal sweep).
The flexibility of the amplifier plug-in units available for
use with the 7844/R7844 provide the means of applying ex
ternal signals to the horizontal deflection system.
Installation of a 7A-series amplifier plug-in u n i t in one of the
horizontal and one of the vertical compartments provides
x-y operation, For further information, refer to the horizon
tal specifications in this manual and to the instruction manual
for the amplifier units.
Some of the 7B series time-base units can be operated as
amplifiers in addition to their normal uses as time-base
generators. This feature allows an external signa! to provide
the horizontal deflection to the crt. For most of the time
base units with the amplifier function, the
X
(horizontal)
deflection signal can be connected either to an external in
put connector on the time-base unit, or it can be routed to
the time-base unit through the internal triggering system
(see time-base instruction manual for detail s ) . I f the latter
method is used, the A and B T R I G SOURCE switches must
be set so that the
X
(horizontal) deflection signal is obtain
ed from one of the verflcal amplifier units and the Y (verti
cal) deflection signal is obtained from the other vertical
unit. The attenuator switch on the amplifier u n i t carl p ro
vide the horizontal with a preconditioned signal, compati ble
to the horizontal deflection factor. Also, plug-in units need
not be moved between compartments when changing from
X-V
operation to other modes of operation.
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