Tektronix 2221 User Manual

Operating
considerations -
2221
Operators
input connections as short as possible to maintain the
best
waveform
fidelity .
2. Touch the probe tip to the oscilloscope GND
connector .
3. Wait
several
seconds
for
the input -
coupling
capaci
tor to
discharge
.
Misadjustment of probe compensation is a common
source of
measurement error
. Due to
variations in oscillo
scope input characteristics , probe compensation should be
checked and adjusted , if necessary , whenever the probe is
moved from one oscilloscope to another or between chan
nels . See
the probe compensation procedure
in
" Operator's Check and Adjustments " or consult the
instructions
supplied with
the
probe
.
4.
Connect
the
probe tip to
the signal source
.
5. Wait several seconds for the input - coupling capaci
tor to charge to the dc level of the signal source .
Coaxial Cables
6. Set the AC - GND - DC switch to AC . A signal with a
large dc
component can now
be
vertically positioned
within
the graticule area , and the ac component of the signal can
be
measured in the
normal manner .
Cables may also be used to connect signals to the ver
tical input connectors , but they may have considerable
effect on the accuracy of a displayed waveform . To main
tain the original frequency characteristics of an applied sig
nal , only high
- quality , low
- loss
coaxial cables should
be
used . Coaxial cables should be terminated at both ends in
their characteristic impedance . If this is not possible , use
suitable impedance - matching devices .
PLOTTING THE GRATICULE
INPUT -
COUPLING
CAPACITOR PRECHARGING
|
The graticule is not normally plotted in MANUAL PLOT ,
but it is plotted on the first acquisition after the AUTO
PLOT mode
is
entered
.
Multiple AUTO plots
may be
avoided and the graticule still plotted in MANUAL in one of
the
following
ways
:
uu
1. If the
instrument
is
acquiring
normally
, put the
instrument in AUTO PLOT . Wait for the plot to start . Exit
AUTO PLOT
before the plot
finishes .
When the input Coupling switch is set to the GND posi
tion , the input signal is connected to ground through the
input - coupling
capacitor and a
high resistance
value . This
series combination forms a precharging circuit that allows
the input - coupling capacitor to charge to the average dc
voltage level of the signal applied to the input connector .
Thus , any large voltage transients that may accidentally be
generated are not applied to the vertical amplifier input
when the input coupling is switched from GND to AC . The
precharging network also provides a measure of protection
to the external circuitry by reducing the current level that
is drawn
from the
external circuitry while the
input
coupling capacitor is charging .
2. In cases where no acquisitions are being made
( Save , no valid triggers , etc. ) , the information can be plot
ted by putting the instrument in AUTO PLOT and pushing
the MANUAL PLOT button . The graticule and other infor
mation will be drawn as if it were the first plot of an Auto
Plot cycle . Exit Auto Plot before making
another
acquisition unless
Auto Plot
mode is
desired
.
If AC input coupling is in use , the following procedure
should be followed whenever the probe tip is connected to
a signal source having a different de level than that previ
ously applied . This procedure becomes especially useful if
the dc - level difference is more than ten times the
VOLTS /
DIV
switch
setting .
CANCELING A PLOT
1
Changing any of the following controls cancels plots in
progress
:
VECTORS ON / OFF , ACQUISITION MODE ,
TRIG POSITION , STORE / NON - STORE , VERTICAL MODE
( except BW LIMIT ) , SEC / DIV , VOLTS / DIV , CH 1 or CH 2
Coupling , Probe Code , CH 2 INVERT , or TRIGGER mode .
1. Set the AC - GND - DC ( input coupling ) switch to GND
before
connecting the probe
tip to a signal
source .
4-2

Tektronix 2221 Specifications

General

Brand	Tektronix
Model	2221
Category	Test Equipment
Language	English