Tektronix 3B5, Instruction Manual

Page: 21 / 187

Operating Instructions—Type 3B5
the correct display. If a trigger signal still is not present
the NOT TRIG'D readout comes on and no sweep-rate
seeking is performed; the sweep free runs (normally at two
seconds/division). However, if a subsequent seek command
is received and the correct trigger signal is then available
for the original setting of the trigger controls, the seek circuits
allow the trigger circuit to return to the original mode of
operation. Trigger seeking as just described insures a cor­
rectly triggered display in the Seek Mode even if the Trigger
Function switch is set to the wrong position, the LEVEL control
is incorrectly set or a trigger signal is not applied (external
triggering).
External Mode
General. Most of the functions of the Type 3B5 can be
externally programmed through the front-panel PROGRAM
connector in the External Mode. This feature allows the Type
3B5 to be set up for previously established conditions for
use in assembly-line testing or similar repetitive measurement
applications. When External Mode operation is used, all
functions must be externally programmed (note exceptions
shown in Table 2-2 for trigger function, trigger slope and
horizontal position). Operation in the External Mode is
basically the same as just described under General Oper ­
ating Information. A programmer which has facilities for
programming all External Mode parameters of the Type 3B5
and the associated automatic/programmable amplifier unit
is available from Tektronix. However, the following informa ­
tion is provided if the operator desires to design his own
programmer.
Program connector. Fig. 2-8 shows the front-panel PRO
GRAM connector, J30, with all terminals identified as to their
function. (Notice that some of these terminals are used for
functions other than External Mode programming.) The view
shown of J30 is as seen when looking at the front panel of
the Type 3B5 (same as when looking at the rear of the
mating connector).
Current ratings. Table 2-1 lists the maximum power ­
supply current which can be drawn out of the Type 3B5
through the PROGRAM connector. Table 2-2 lists the cur­
rent which flows through the terminals of the PROGRAM
connector when the associated program is actuated (ground­
ing logic). Any external switches or components must be
capable of handling this current.
Maximum Power Supply Current Available from J301
TABLE 2-1
J30 Terminal Current (milliamps)
1 (- 12.2 V)
75
18 ( +125 V) 30
19 (-100V)
1
'Maximum available current when used with an amplifier unit which
also draws maximum current.
Program logic. Both digital and analog program logic
levels are used in the Type 3B5. For functions which require
a switching action (e.g., trigger function), digital logic is
used. To activate a digitally programmed function, grounding
logic (zero volts) is applied. The function is inactive when
the circuit is left open (or a — 1 2-volt holding level is
applied). Notice the typical currents listed in Table 2-2 which
must be supplied when the logic level is zero volts (function
active). Analog logic is used for functions which require a
variable program (e.g., trigger level). The analog functions
are programmed by connecting a program current to the
applicable terminal of J30. This current should be variable
over the range given in the typical current column of Table
2-2 to provide a full range of external program adjustment
Establishing the program. Table 2-2 lists all program ­
mable functions of the Type 3B5, the applicable PROGRAM
connector terminal and the type of logic required. Refer
to Fig. 2-8 for location of the terminals within the PROGRAM
connector.
TABLE 2-2
Programmable
Function
Logic
Type2
J30
Terminal
Typical
Current
Trigger Function
Int Auto Absence of function program
selects Auto (front-panel LEVEL
control operative)
Int AC Digital 31 3 milliamps
Ext AC Digital
30 15 milliamps
Ext DC Digital 28 30 milliamps
Trigger Slope
+Slope Absence of slope program
selects + slope
—Slope Digital
17 3 milliamps
Sweep Multiplier 3
X 1 Digital 2
5 milliamps
X2 Digital 3
5 milliamps
X5 Digital 5
5 milliamps
Sweep Decade 3
1 s, 0.1 s Digital 6
10 milliamps
10 ms, 1 ms
Digital
8
10 milliamps
0.1 ms, 10 μ s Digital 9
10 milliamps
1 μ s, 0.1 μ s
Digital 11 10 milliamps
10 ns Digital 26
20 milliamps
Decade Enable 3
A (Is, 10 ms,
0.1 ms, 1 /is
Digital 23
5 milliamps
B (0.1 s, 1 ms, 10 μ s,
0.1 μ s, 10 ns)
Digital 24
5 milliamps
Sweep Magnification
X1 (OFF) Digital 33
25 milliamps
X10
Digital 34 15 milliamps
X100 Digital 36
15 milliamps
External Mode
Command
Digital 21
5 milliamps
Trigger Level Analog 15
~0-400 micro ­
amps range
Horizontal Position Analog
14 ~0-500 micro ­
amps range 4
Delay Analog
17
^200-350 mi­
croamps range
Digital logic is grounding logic (zero to — 1 volt) for an active
program and open circuit (or —12 volts holding level) for an
inactive program. Analog functions are current programmed.
Sweep multiplier, sweep decade and decade enable logic must be
programmed for each sweep rate (see Table 2-3).
'Operates as a vernier for the front-panel POSITION control. Both
controls can position trace.
2-13