Operation Model
8904A
lbble
3-10.
Output Amplitude Ranges and Their Associated Attenuators
for
the
HP
8904A
10.00
5.00
2.50
1.250
0.625
0.31 2
0.1 563
78.13
39.06
19.53
9.765
4.882
2.441
1.221
0.61
0
0.305
to
5.01
to
2.51
to
1.251
to
0.626
to 0.313
to
0.1564
to
0.0782
to 39.1
to
19.6
to 9.766
to
4.883
to
2.442
to
1.222
to
0.611
to
0.306
to
0.153
V
V
V
V
V
V
V
mV
mV
mV
mV
mV
mV
mV
mV
mV
0
6.02
12.04
18.06
24.08
30.10
36.1 2
42.14
48.1 6
54.1
8
60.21
66.22
72.25
78.27
84.29
90.31
none
6 dB
12 dB
6,12 dB
24 dB
6,24 dB
12,24 dB
6,12,24 dB
48 dB
6,48 dB
12,48 dB
6,12,48 dB
24,48 dB
6,24,48
dB
12,24,48 dB
6, 12, 24,48 dB
~~
Actual
Resolution
2.4414
mV
1.2207
mV
0.6104
mV
0.3052
mV
0.1526
mV
76.2939
uV
38.1470
uV
19.0735
uV
9.5367
uV
4.7684
uV
2.3842
uV
1.1920
uV
1.0000
uv
1.0000
uv
1.0000
uv
1.0000
uv
The multiplier is used to “fill-in” the fine level steps between the
6
dB
analog attenuator steps,
Approximately half of the
12
bit scale of the multiplier
is
used for setting the fine levels. This
means that for each
6
dB
wide window there are
2048
possible fine amplitude steps:
212
=
4096
=
2048
While this arrangement yields
a
constant number of steps per
6
dB
attenuator range, the
resolution in volts is twice as fine for every
6
dB
attenuator used.
For
example, the actual
resolution in the
10
to
5.01
V
range
is:
lOV-SV(neztfullscclle?ange~
-
5
--
2040steps
2040
Resolution
=
2.441
mV
For
the
5
to
2.51
V
range the resolution is:
Resolution
=
20~~~ps
Resolution
=
1.222
mV
The minimum resolution
is
limited
to
1
pV
for the bottom of four ranges.
As
mentioned
before, this fine resolution is not displayed on the front panel due
to
lack of display space.
Steps this fine may be programmed over
HP-IB
or input from the front panel. To
get
small
steps from the front panel, the amplitude increment function must be used.
For
example, on
the
10
volt full scale range
an
amplitude increment of
2.44
mV could be set. The the amplitude
can be stepped up or down by this amount using the
fl.
or
4
keys. The display does not change,
however, until enough steps have occurred to
alter
the
3;
digits of displayed resolution.
3-40
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