Fluke 93 Service Manual page 56

3-22
CIRCUIT
DESCRIPTIONS
Table 3.7
Frequencies
of
A-
AS
IC signals
In
various
modes^
Time Base
TRACKN
freq
1)
CHA
freq
1)
MODE
horizontal vertical
60
s/div
0.8333
Hz
0.416
Hz
~r
_
20
s/drv
2.5
Hz
1.25
Hz
roll
i
10
s/div 5
Hz
2.5
Hz
,
5 s/div 10
Hz
5
Hz
-
-
T
2
$/div 25
Hz
12.5
Hz
i
1
s/dIv
50
Hz
25
Hz C
.5 s/div
100
Hz
50
Hz H
.2
s/div
250
Hz
125
Hz s
0
.1
s/div
500
Hz
269
Hz
p
50
ms/dlv
1
kHz 500
Hz
N
20
ms/div
2.5
kHz
1.25
kHz
G
F
10 ms/div
5
kHz
2.5
kHz L z
5 ms/div 10 kHz
5 kHz
E
z
i
\
2 ms/div 25 kHz
12.5
Id-fz
_
1
ms/div 50 kHz
25 kHz
.5
ms/div 100 kHz 50 kHz
f
•
r
.2
ms/div
260 kHz
125 kHz
E
i
.1
ms/dlv
600 kHz 250 kHz
C
50
ps/div
1
MHz
500 kHz U
1
z
20
ps/div 1.25
MHz "
r
R -
10 ps/div 2.5
MHz
R
5
ps/div 5
MHz
Trigger
E
z
2 ps/div
12.5
MHz
N
A
. '
1
ps/dfv
25
MHz
dependent
T _
.5
ps/div
25
MHz
1
r
.2
ps/div
25
MHz
f
.1
ps/div
25
MHz
m
50
ns/div
25
MHz
20
ns/div
25
MHz
f
1
f
10
ns/div
25
MHz
1 )
In
MtN/MAX mod^
(only
possible
for
one
channel), the frequency
of
CHA
is
zero
and
the
sample
frequency
TRACK
Is
always 25 MHz.
Clamp
To
prevent
the
Track &
Hold
circuit
from
overdrive, the signal
is
damped. The
level
of the output
signal
can be
adjusted by
means
of
VREF
(input 23).
VREF
is
the reference
voltage,
made
by ihe
circuit
consisting of
V2301,
V2302 and R2323,
R2324,
and
R2325
(see
ADC
section).
Track A Hold
The
maximum
sampling frequency
of
the
ADC
used
in
the
ScopeMeter
is
25 MHz.
This
means
that
the
ADC
can
only
handle
signals with
frequencies
up
to
12.5
MHz
(half the
sample
frequency).
Because
of
this
a Track
&
Hold
circuit
Is
incorporated
In
the
A-ASIC. The
Track
&
Hold
circuit
determines
the
frequency range
of the
whole
system.
The
timing
in
this
part
of the
A-ASlC
(s
determined by
clock signal
TRACKN
(input
1 2).
The
frequency
of the
TRACKN
signal
depends on
the selected
timebase
speed
(see
table 3.7).