Advanced Features
Glitch Detect
This facitilty allows the user to
capture
transients, as brief as
5ns, which may occur
at
any time during the normal sample
period. This feature
is
only available on timebase ranges
upto Sus/div.
The
four options are:
Off
No glitch detection
Max Instead
of
displaying
the
normal sample point,
maxima are
detected
between
the
samples
and
these
will be shown instead.
Min Instead
of
displaying the normal sample point,
minima are
detected
between
the
samples
and
these
will be shown instead.
Max-Min
The
4070 will alternately look for maxima
and
minima.
If
there
is
an
alias being displayed, (see
Scctic:1 1.1) by selecting
'Max-Min'
this will be dis-
played as two horizontal lines,
one
formed from
the
maxima
and
the
other
from
the
minima.
These
two
horizontal lines
are
formed alternately
one
dot
high
and
one
low, i.e. maxima
then
minima.
Interpolation
Various methods
are
available for joining
the
sample points
on
the
screen display: these options
are
particularly useful
with X
Mag
and
at
fast timebases.
Off
No
interpolation will
be
performed.
Normal
The
usual dot-joiner will
be
active: this shows
the
sample points as bright dots and draws a line bet-
ween them.
Linear
Extra
points
are
inserted between
the
expanded
'real'
sample points.
The
extra points
are
placed
on
an
imaginary line joining
the
true samples.
This
is
the
default selection.
Sine
Extra
points
are
inserted between
the
expanded
'real'
sample points.
The
interpolator assumes
that
the
input
is
sinusoid in
content
and
may add a small
amount
of
preshoot
or
overshoot
on
fast squarewiive
edges.
Other Options
ADD
CHI
+ CH2 This option adds
the
inputs
of
Channel 1
and
Channel
2, displaying
the
results in
the
Channel 1
traces.
The
addition is
performed
prior
to
any Glitch
Detect
or
interpolation operations.
ADD CH3
+ CH4 (4074 only) This option adds the inputs
of
Channel 3 and
Channel
4, displaying
the
results in
the
Channel 4 trace.
The
addition
is
performed
prior
to any
Glitch
Detect
or
interpolation operations.
Bandwidth Limit
The
full bandwidth
of
the
4070 is
lOOMHz: this option allows it
to
be
reduced
to
20MHz when
the
full bandwidth
is
not
required.
52
Section 2
AVERAGING
It
is
possible
to
improve
the
signal
to
noise
ratio
of
the signal by averaging.
The
4070 uses continuous
averaging and the algorithm used
is
An
=
an
*(f
- 1) +
dn
f
Where:-
n = The data point
(1
to 1008)
An
= New value
at
n
an
= Old value
at
n
f = averaging factor (2
to
256)
dn
= Latest value
at
n
The
options for averaging factor
are:-
Off
(no averaging), 2, 4, 8, 16, 32, 64, 128
or
256.
If
Glitch
Detect
is
also selected any non-repetitive glitches
will be reduced in magnitude by
the
effects
of
the
averaging.
When
many traces are averaged together
the
signal
to
noise
ratio
is
increased by a factor
of
the
square
root
of
the
number
of
averages.
For
example, if 256 averages were
selected
the
signal
to
noise ratio would
be
improved by 16
to
one,
or
24dB.
NOTE: S/Shot.
If
Averaging is selected
and
is pressed
the
4070 will capture only 1 sweep with
no
averaging. Averag-
ing
is
not available in Roll mode.
To
capture and average a fixed
number
of
sweeps is only
possible using the optional waveform processor (see
section 6).
2.5 THE HELP
MENU
This menu comprises five pages
of
assistance for
the
user.
2.6 SAVE
AND
RECALL SETUP
MENU
This
menu
allows
the
user
to
manipulate
the
contents
of
the
four setup memories: new setups can be saved,
or
already
saved setups can be recalled. Recalling a setup does not
clear the memory from which it
is
recalled,
but
when new
setups are saved,
the
original contents
of
the
relevant mem-
ory will be lost.
A setup comprises
the
following:
1.
the attenuator settings;
2.
the
timebase settings;
3. the trigger
so11rce,
coupling, slope
and
level set-
tings;
4.
the
trigger time
and
event
delay settings;
5. the trigger processor
setup;
6. the
GPIB
and RS423 setups;
7.
the
default plotter.
To
save a setup, select
the
menu,
then
choose which mem-
ory to store the setup in by pressing
the
appropriate
numeric button
(I
to 4).
The
setup
will be saved and the old
contents
of
that memory will
be
lost.
To
save trace informa-
tion see
Section 2.0.
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