Controls, Connectors, and Indicators—2445 Operators
(2?) CALIBRATOR Connector—Provides a 0.4-V p-p
square-wave signal into a 1-M£2 load, a 0.2-V p-p
square-wave signal into a 50-12 dc-coupled load, or
an 8-mA p-p square-wave current signal into a short
circuit at a sweep speed of 1 ms per division. The
CALIBRATOR output signal is useful for checking
the sweep, the delays, and the vertical deflection
accuracies, as well as compensating voltage probes
and checking the accuracy of current probes. The
repetition rate of the square wave changes with the
setting of the A SEC/DIV switch. For all sweep-speed
settings from 100 ms per division to 100 ns per
division, the A Sweep display, as seen on the instru
ment supplying the CALIBRATOR signal, will be
five cycles per 10 divisions. At 100 ms per division
and slower, the CALIBRATOR frequency will be
5 Hz; at 100 ns per division and faster, the frequency
will be 5 MHz. The signal amplitude at 5 MHz will be
at least 50% of the signal amplitude obtained when
the sweep speed is set to 1 ms per division.
NOTE
Due to internal circuitry constraints, the
calibrator signal is not synchronized during
trace holdoff. This does not affect the accuracy
o f the calibrator signal that is present during
a trace display. However, if the 2445 CALI
BRATOR signal is used to calibrate other
instruments, the sweep of the 2445 must be
shut off. I f it is not, the signal will appear to
jitter and will give false (low) frequency counts.
The sweep of the 2445 is easily shut o ff by set
ting the TRIGGER MODE switch to SGL SEQ.
(22) Auxiliary Ground Jack—Provides an auxiliary signal
ground when interconnecting equipment under test
and the oscilloscope. Hookup is made via a banana-tip
connector.
HORIZONTAL AND
DELTA MEASUREMENT
Refer to Figure 3-4 for items 23 through 33.
(23) A SEC/DIV Switch—Selects 25 calibrated A Sweep
speeds from 1 s per division to 10 ns per division, or
delay ranges from 10 s to 200 ns, in a 1-2-5 sequence.
Extreme counterclockwise switch rotation selects the
X-Y display mode. In X-Y, the signal applied to the
CH 1 OR X input connector drives the horizontal
deflection system.
(24) B SEC/DIV Switch—Selects 21 calibrated B Sweep
speeds from 50 ms per division to 10 ns per division
in a 1-2-5 sequence. This switch also controls Hori
zontal Display Mode switching, as explained in the
following descriptions.
Knobs Locked—When both the A SEC/DIV and
B SEC/DIV switches are set to the same sweep
speed and the B SEC/DIV knob is pushed in, the
two knobs are locked together; in this position,
only the A Sweep is displayed on the crt.
PULL-1NTEN—Pulling the B SEC/DIV knob to the
out position intensifies the A Sweep display for
the duration of the B Sweep time. When both the
A SEC/DIV and B SEC/DIV switches are set to the
same sweep speed, the B Sweep is not displayed,
but it runs at one of two speeds: either 100 times
faster than the A Sweep speed or at 5 ns per
division, whichever is slower. The A and B SEC/
DIV knobs are interlocked to prevent the B SEC/
DIV switch from ever being set to a slower sweep
speed than the A SEC/DIV switch setting.
The position of the intensified zone on the A
Sweep indicates the delay time between the start
of the A Sweep and start of the B Sweep interval.
Its position is controlled by the A REF OR DLY
POS control.
For single-trace displays, when either the Delta
Time (At) or the reciprocal Delta Time (1/At)
function is activated, two intensified zones will
Figure 3-4. Horizontal and delta measurement controls.
3-4
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