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G
R
ATIC
ULE
The graticule is inte rn ally marked on t h e face
p
late of th e
crt to enable accu rate measurements with out parallax error
(see
F
ig ure 3-1) . It is marked with eight vertical and ten
h
ori-
zo ntal major
d
ivisions.
E
ac h major division is
d
ivi
d
e
d
into
five sub
d
ivisions . The vertical
d
eflection factors and
h
orizon-
tal timing are calibrated to t h e g r aticule so that accurate
measurements ca n be made
d
ir ectly fr om th e c rt. Also, per-
ce ntage mark e r s fo r
t
h e meas ur eme nt of rise and fall times
are located on the left side of t h e g r aticule.
G
R
O
UN
DI
N
G
T
he most
r
elia ble signal measu r eme n ts are made when
the 2213 Α and th e u nit
u
nde r test are connected by α com-
mon
r
efe r e n ce (ground lead), in
a
ddition to the signal lea
d
or
p
robe . The probe's ground lea
d
provides the best grounding
method for signal interconnection and ensures the maxi-
mum amount of signal-lead shielding in
t
he
p
robe ca ble .
Α sepa rate ground lead can also be connecte
d
from the unit
under test to the oscillosco
p
e GND co nnector locate
d
on
the front
p
anel .
SIG
N
A
L
CO
NNE
CTIO
N
S
Ge nerally,
p
robes offer the most convenient mea n s of
connecting an in put signal to the instrume nt. Th ey are
shielded to
p
revent pickup of electromagnetic interference,
and the su pplie
d
10 Χ
p
robe offers α
h
ig h
i
np ut impedance
that minimizes circ uit loading. This allows the circuit u n der
test to operate with α minimum of change from its
n
ormal
co n
d
ition as measurements are bei ng ma de.
Coaxial cables may also be
u
sed to connect signals to
the in put co nnectors, but they may
h
ave considerable effect
on th e acc uracy of α displayed waveform . To maintain the
original fre quency c haracteristics of an applied signal,
only
h
ig h-
q
uality, low-loss coaxial cables should
b
e
u
sed.
Coaxial cables should be terminated at both ends in
t
heir
c h aracte ristic im pe
d
ance . If this is
n
ot
p
ossi ble, use suitable
impedance-matc hing devices.
I
NPU
T CO
UPL
I
N
G
CA
P
ACITO
R PRE
C
H
A
R
GI
N
G
When
t
he In
p
ut Cou
p
ling switch is set to GND, the input
signal is co nnecte
d
to ground through
t
he in
p
ut coupling
ca pacitor in series with α 1 ΜΩ
r
esisto r to fo rm α
p
rechargi ng networ k. Th is
n
etwo rk allows th e in
p
ut coupling
capacitor to charge to t h e average dc-voltage level of the
signal applied to t h e probe . Th us any large voltage
transients that may accidentally be generated will not
b
e
applied to the am
p
lifier input when the Input Coupling switch
is moved from GND to AC . The precharging
n
etwork also
p
rovides α measure of
p
rotectio n to the exte rnal ci rcuitry by
redu cing the cu rrent levels that ca n be
d
rawn
f
rom the ex-
ternal circuitry during ca
p
acitor charging .
The following procedure shoul
d
be used whenever the
probe ti p is connected to α signal source
h
aving α different
do level than
t
hat previously a
pp
lied, es p ecially if t h e dc-
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