Control Hlumination; Calibrator Output; Probe Power; Horizontal Display Mode Combinations - Tektronix 7844 Instruction Manual

Operating instructions-7844/R7844 Operators
2. Adjust the vertical and horizontal Position controls to
center the display on the graticule.
3. Release the BEAMFINDER switch; the display should
remain within the graticule.
Control Illumination
The CONTROL ILLUMINATION switch sets the illumina-
tion level of the lighted push button switches on the plug-in
units. The positions available are OFF, LOW and HIGH.
This switch is located on the rear panel of the 7844 and the
left side panel of the R7844. The CONTROL ILLUMINA-
TION switch does not affect the function indicator lights
(such as TRIG'D lights or SINGLE-SWEEP READY lights).
Calibrator Output
The internal calibrator provides a convenient signal for
checking basic vertical gain and sweep timing. The calibra-
tor signal is also very useful for adjusting probe compensa-
tion as described in the probe instruction manual. In addi-
tion, the calibrator can be used as a convenient signal source
for application to external equipment. See Table 2-1 in the
Specification section for calibrator accuracy.
VOLTAGE. The calibrator provides accurate output voltages
at the CALIBRATOR Output connector from 4 millivolts
to 4 volts in decade steps into loads of more than 100 kil-
ohms. In addition, it provides from 0.4 milfivolts to 0.4
volt into a 50 ohm load.
CURRENT. The current loop provides a 40 milliampere
output which can be used to check and calibrate current-
measuring probe systems. The current output is selected by
the CALIBRATOR switch when set to the 40 mA position.
The current signal is obtained by clipping the probe around
the current loop. The arrow above the current loop indicates
conventional current flow; i.e., from plus to minus. Forty
milliamperes is available from the R7844 when the optional
current loop adapter is used (Tektronix part G12-0031-00)
and the CALIBRATOR is set for a 4 volt output.
REPETITION RATE, The repetition rate of the calibrator
is 1 kilohertz. The calibrator circuit uses frequency-stable
components to maintain accurate frequency and constant
duty cycle. Thus, the calibrator can be used for checking
the basic sweep timing of time-base units.
WAVE SHAPE. The square wave output signal of the cali-
brator can be used as a reference wave shape when checking
or adjusting the compensation of passive, high-resistance
probes, The square wave has a flat top so any distortion in
the displayed waveform is due to improper probe compen-
sation.
Probe Power
Two PROBE POWER connectors on the rear panel of the
7844 and the front panel of the R7844 provide power for
accessories. Current from these connectors is limited, there-
fore it is not recommended that they be used as a power
source for applications other than the compatible probes or
other accessories which are specifically designed for use
with this system.
Horizontal Display Mode Combinations
The HORIZONTAL MODE switch allows both beam 1 and
beam 2 to be controlled by either A HORIZ or B HORIZ
compartments. When both beams use the same time-base
unit as a sweep source, the other unused horizontal compart:
ment can be used for special purpose plug-in units such as a
counter, digital voltmeter, etc.
The HORIZ SEP (1) control provides horizontal position-
ing of beam 1 in addition to the Position control of the
horizontal plug-in unit selected by the BEAM 1 HORIZON.
TAL MODE switch. When the same time base is selected
for horizontal deflection of both beams, the HORIZ SEP (1)
control can be used to align an event on the beam 1 trace so
that the timing of both beams coincide.
Vertical Display Mode Combinations
The 7844/R7844 Option 21 model has dedicated vertical
plug-in compartments, The left vertical compartment is
directly connected to the beam 1 trace and the right vertical
compartment is directly connected to the beam 2 trace.
The 7844/R7844 standard model has vertical crossover
switching. The VERTICAL MODE switch allows both the
beam 1 and beam 2 traces to be controlled by either vertical
plug-in compartment. When both beams are being controlled
by the same vertical compartment, the VERT SEP {1} con-
trol becomes operational. The VERT SEP (1) contro! will
position the beam 1 display above or below the beam 2
display.
Beam 2 Display Characteristics
The readout display is produced on a time-shared basis with
the beam 2 crt display in both the PULSED and free-run
(non-pulsed) READOUT modes.