Tektronix 7A22, Instruction Manual

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Operating Instructions-Type 7A22
IAJ Signal applied to + INPUT.
I C J Resultant display.
ISJ Signal applied to -INPUT.
Fig. 2-8. Waveforms showing differential reiection of a common-mode signal. Resultant waveform Icl shows the difference between the two
signals.
DC Offset Operation
By using the DC OFFSET controls, it is possible to use the
Type 7 A22 differentially in a slide-back mode, to observe
small signal whose DC potential difference may be consider­
able. The offset is continuously adjustable from
+
1 V to
--1 V when the VOLTS/DIV switch is in the 10 fLY to 1 0 mV
positions. In the 20 mY, 50 mV and .1 V positions of the
VOL TS/DIV switch, the 1 V offset is effectively multiplied by
the input attenuator to a range of ::L: 1
a V. Table 2-1 sum­
marizes the effective DC offset voltages internally available
for all the VOLTS/DIV switch positions. The table also lists
the input attenuator that is switched into the amplifier circuit
for the various VOLTS/DIV switch positions.
TABLE 2-1
VOL TS/DIV setting
OFFSET RANGE ATTENUATOR
in
,=-c;"c:oc,,'=�:::,-'c"";=_=-_:"''''_'''c,,_,_;_,-; _ _ ,_,.-__ oc,;:;,-:::;
10 fLY to 10 mV ::+.:: 1 V lX
20 mV to 0.1 V ± 1 0 V
lOX
--------------"-----------
-------------------- ---- ----"---
--------
-
- ------ - --
0.2 V to 1 V
.::t_:
100 V
2
V
to
16v------------�±
1000 V"
100 X
1000X
'CAUTION-
± 500
volts is the maximum allowable signal voltage
of each input.
®
Using the DC OFFSET functions:
Set the Type 7 A22 controls as follows:
VOLTS/DIV
VARIABLE (CAL IN)
POSITION
AC-GND·DC
(--t-
and -- INPUT)
1 0 V
CAL
Midrange
GND
1 MHz
DC
HF ---3 dB POINT
LF --3 dB POINT
STEP A HEN DC BAL Adjusted for DC balance
1 . Position the trace to graticule center (or some other
convenient reference line) using the POSITION control.
2. Connect a coaxial cable from the signal source to the
+INPUT.
3. Set the + INPUT AC-GND-DC switch to DC and meas­
ure the DC level to be offset.
4. Set the VOLTS/DIV to the largest deflection factor in an
offset range which will encompass the DC level measured in
step 3. See Table 2-1 and front panel color bands.
5. Set the LF --3 dB POINT selector to DC OFFSET.
2-11