Tektronix 3B4 Instruction Manual page 5

SECTION 1
CHARACTERISTICS
Introduction
The Type 3B4 Time Base plug-in unit is designed to be
used primarily with the Tektronix Type 561A Oscilloscope sys-
tem; however, It can also be used with the other 560-Seriés
systems that use 3B-Series plug-in units such as the Type 564
and Type 567. As part of an oscilloscope system, the Type
3B4 is used as an accurate time base generator or as a
calibrated amplifier for externally generated deflection sig-
nals,
When used with the 567 or RM567, the 3B4 provides a time-
base, but does not activate the digital readout circuitry.
In the 565 or RM565, the 3B4 provides a vertical time-base
for raster applications but does not provide retrace blanking.
The Type 3B4 provides calibrated sweep rates from 0.05
psec/div to 5sec/div in 25 calibrated steps. A five-step,
direct-reading magnification feature provides magnification
up to 40X or 50X, depending on the sweep rate to which
magnification is applied. When the Type 3B4 is used as an
amplifier for externally generated deflection signals, the
magnifier provides five steps of deflection sensitivity, from
0.2 volts/div to 5 volts/div. In addition, a variable control
provides uncalibrated sweep rates and deflection sensitivities
between the calibrated steps. By using the variable control,
uncalibrated sweep rates from 0.05 psec/div to approxi-
mately 12.5 sec/div and deflection sensitivites from 0.2 volts/
div to approximately 12.5 volts/div are available. Uncali-
brated operation is indicated by a neon lamp.
Normally, the Type 3B4 is inserted in the right-hand com-
partment (operator's right, oscilloscope's left) of the oscillo-
scope and in this position provides horizontal deflection.
When used with the Type 561A, the Type 3B4 can be inserted
into the left-hand compartment of the oscilloscope to provide
a time base that runs vertically on the crt screen. Due to
differences in the horizontal and vertical deflection plate
sensitivities, the Type 3B4 must be calibrated for vertical
deflection use if accuracy is required in such application.
This manual is written with the assumption that the Type 3B4
will normally be used to provide horizontal deflection sig-
nals in a Type 561A.
Triggering
Facilities
TRIGGER MODE Switch Free Run, Auto, Normal,
and Single Sweep
TRIGGERING LEVEL Con- See Tables 1-1 and 1-2.
trol
SLOPE Switch + or —
COUPLING Switch Ac, Ac Low-Frequency Re-
ject, and Dc
SOURCE Switch Internal, Line, External,
and External + 10
TRIGGERING LEVEL Control Voltage Range (external
triggering}
See Table 1-1.
TABLE 1-1
Voltage Range
SOURCE COUPLING Typical Minimum
AC, DC or
EXT AC LF REJ +19 ¥ +15
AC or DC +190 v
EXT + 10 AC LF REJ +150 v
NOTE
The voltage range of the TRIGGERING LEVEL con-
trol indicates the maximum external peak voltage
that will permit triggering at any amplitude point
on the signal. Signals with greater amplitudes can
be used and will provide triggering, but the range
of trigger-point selection is still limited to the TRIG-
GERING LEVEL control voltage range.
Triggering Sensitivity. See Table 1-2.
@1
TABLE 1-2
SOURCE
Voltage Range
AC
AC LF REJ DC
INT
1 minor division of
deflection 30 cps to 20
mc. Outside these
limits requires larger
triggering signal.
1 minor division of
deflection 30 kc to 20
mc. Outside these
limits requires larger
triggering signal.
1 minor division of
deflection dc to 20
me (with trace verti-
cally centered}, Above
20 mc requires larger
triggering signal,
EXT
0.5v 30 cps fo 20 mc.
Outside these limits
requires larger trig-
gering signal.
0.5v 30kc to 20mc.
Outside these limits
requires larger trig-
gering signal.
0.5v dc to 20mc.
(with trace vertically
centered). Above 20
mc requires larger
triggering signal.
1-1