Mode
IS3
1SA/B
Operation
which
allow
s the adjustable Trigger
Le
vel to be
positioned
at the
optimum
point.
Set
the Trigger Level
control
to
the
appro
ximate
center
of
the
trigger
ing range
ind
icated by
the
trigger
light
(see
Figure
3-7).
Figure
3-7.
DC
Coupled
Mea5urements
3.
When
input
l
oading
is a
problem
(i.e
.,
1
MO
load
or
cable capacitance)
or
whe
n a
more
convenient
method
of
probing
is
desirable, use a 10:1 Scope Probe. A
prob
e
is
r
ecom-
mended
for
all
logic
application
s.
4.
For sine wave measure
men
ts
<100
kHz,
always use the
low
pass
filter,
se
lectable
on
th
e
front
panel.
Norma
lly
the
input
signal
is
int
egrated
over
the
ent
ir
e 100 M Hz
bandwidth.
Use of the Filter
effectively
removes
noi
se
and harmonics (above 100
kHz
), that may
affect the
correct
measurement.
5.
When
measuring Power Line frequencies, be ex
treme
ly careful and alwa
ys
us
e a step-
down
isolation
transformer
(w
ith
"'
lOV
output
). The
counter's
panel
is
typically
at sign
al
ground,
so
NEVER
tr
y
to
measure
the
50
or
60
Hz
line
w
ithout
an isolation transfor
mer.
Fifty percent
of
the
time, you
will
get
the
connection
reversed and the
cou
nt
er
will
go
up
in smoke, and maybe
the
operator.
too.
6.
Be
very caref
ul
wi
th
input
levels at
higher
frequencies (greater than 5
MHz
). The
co
unter
front
end
can take
on
ly 6 vol
ts
rms
at
these frequencies.
J..51.
Time
Interval
Measurements
1.
To insure
waveform
fide
lity
during
T.I. measurements, always use dc
coupling.
2.
Meaurements
of
pulse w
id
th,
and
time
between
pul
ses,
are
more
con
veni
ently
made
in
the
COM
A (
common
) posi
tion.
3.
Measuring
extreme
ly fast rise times
is
not
re
comme
nded
because
of
the
di
fficu
lty
of
sett
in
g precise
trigger
level
s.
4.
T.I. Average measurements
on
synch
ronous
frequencies
(any
10
M Hz,
or
ha
rmonic
of,
with stability s
imilar
or
better
than the
in
ter
nal
clock
) are
not
reco
mmended
because
of
a
possible
lock-up
condition.
5. In general, use the GATE TIME co
nt
ro
l
to
vary
the
amount
of
resolution
di
sp
la
yed. This
cont
rol
does
not
affect accuracy.
It
basically
trade
s
off
longer
measurement t
ime
for
more
resolution.
3-9
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