Tektronix 1A2 Instruction Manual page 12

Operating Instructions—Type 1A2
To make the low frequency or non-repetitive display stable,
use either internal triggering on Channel 1 or 2 {from pin
5 of interconnecting plug—see Block Diagram in Section 10)
or use the TRIG OUT connector as the external trigger source.
lf there is no Plug-In position on the oscilloscope Trigger
Source switch, use the signal available at the TRIG OUT con-
nector of the Type 1A2 by connecting a jumper coaxial
cable from the TRIG OUT connector to the oscilloscope
Trigger Input connector and setting the Triggering Source
switch to Ext.
Type 1A2's below SN716 do not have the Plug-In trigger-
ing capability.
NOTE
Use the oscilloscope Plug-In position of the Trig-
gering Source switch in preference to external
patching to obtain optimum bandwidth capabilities
from the Trigger Output Amplifier.
Do not set the oscilloscope Triggering Source switch to
Norm Int or Int (oscilloscope vertical amplifier trigger take-
off signal) because a stable display is difficult and sometimes
impossible to obtain. During dual-trace chopped-mode oper-
ation the Norm Int or Int trigger source is a composite signal
consisting of the signals applied to both channels super-
imposed on, but not synchronized with, the free-running rate
of the chopped-mode switching signal. The switching signal
has a square waveshape the same as the one shown in
Fig. 2-1B. Its amplitude is dependent on the distance that
the traces are positioned apart and the amount of DC com-
ponent contained in the applied signals; its rate is the chop-
ping rate (about 220 kHz).
Since the internal trigger from the oscilloscope vertical
amplifier is a composite trigger during chopped mode of
operation, and the trigger contains a nonsynchronized chop-
ped-mode switching signal, internal triggering may occur
first on one of the applied signals and then on the chopped-
mode switching signal, or vice versa, resulting in an unstable
display.
TABLE 2-1
Signal Coupling Methods
Source Loading
See Fig. 2-3
Accessories Input R and X,
Method Advantages Limitations Required Curves Precautions
1. Open test un- | Simplicity Limited frequency | BNC to Banana | 1 Meg @ and 15 | Stray pickup and
shielded) leads response, subject | Jack adapter (103- | pF at input, plus | spurious — oscilla-
to stray pickup 0003-00}. Two test | test leads tions
leads.
2. Unterminated | Full Sensitivity Limited frequency | Coaxial cable with |} 1 Meg 2 and 15 | High capacitive
coaxial cable response. High ca- | BNC connector(s} pF plus cable ca- | loading
pacitance of cable. pacitance
3. Terminated co- | Full sensitivity. Presents Ry (typi- | Coaxial cable with | R, plus 15 pF at | Reflection from 15
axial cable. Termi- | Full Type 1A2/Os- | cally 509) load- | BNC connectors R, | Type 1A2 end of | pF at input. DC
nation at Type 1A2 | cilloscope band- | ing at end of co- | termination at Type | coaxial can cause | and AC loading
input. width. Relatively | axial. 1A2 input. (BNC | reflections on test point.
flat resistive load- | May need blocking | 50Q Termination, Power limit of ter-
ing. Long cable j capacitor to pre- | 011-0049-00. mination.
with uniform re- | vent DC loading
sponse. or damage to ter-
mination.
4. Same as 3, with | Less reflection from | Sensitivity is re- | BNC Coaxial at- | R, only DC and AC loaa-
coaxial attenuator | 15 pF at termina- | duced {increased | tenuators ing on test point.
at termination tion Deflection Factor) Power limit of at-
tenuator.
5. Tap into termi- | Permits signal to | 15 pF load at tap | BNC Tee and BNC | 1 Meg © and 15 | Reflections from 15
nated coaxial sys- | go to normal load. | point
connectors on sig- | pF at tap point. pF input
tem. (BNC Tee: | DC or AC coupling nal cables
UG-274/U at Type | without coaxial at-
1A2 input). tenuators.
6. 10X, 10MQ | Reduce resistive | X0.1 sensitivity P6006, P6008 are | P6006?:~7 pF, 10 | Check probe fre-
Probe and capacitive | X0.01 sensitivity 10; P6007, P6009 | MQ quency compensa-
10, 10 MQ loading, nearly full | X0.001 sensitivity | are 100; P6015 is | P6007: Less than 2 | tion. Use square-
Probe Type 1A2/QOscillo- 1000 < pF, 10 MQ wave __ frequency
1000X, 100 MQ | scope bandwidth. P6008:-~7.5 pF, 10 | less than 5kHz,
Probe Mo preferably 1 kHz.
P6009:-2.5 pF, 10
MQ
P6015:
100 MQ.
~~
~
27 pF,
2P6006 Probe has less
2-6
input capacitance than P6008, but P6008 has wider bandwidth.
®1