Service Model
8903B
48.N Defeat Output Amplifier Overdrive Protection.
In the ac level and signal-to-noise measurement modes,
the gain of the Output Amplifier is normally set to
0
dl3
whenever the signal detected by the Pre-Notch
RMS/Average Detector exceeds 0.6V and
a
low-pass filter has been selected. This prevents the
first
amplifier after
the Notch Filter from being overdriven by
signals
in the stopband which would normally be detected by the Output
RMS/Average/Quasi-peak Detector. When this Special Function is invoked, the Output RMS/Average/Quasi-peak
Detector is used to determine the gain setting of the Output Amplifier. Use of this function permits measurement
of filters (such as the internal, optional weighting bandpass filters) with extended dynamic range, but care must
be taken not to overload the selected low-pass filter (either
30
or
80
kHz).
N=O Output Amplifier gain determined normally.
N=
1
Output Amplifier gain determined by the Output RMS/Average/Quasi- peak Detector.
49.N Display Internal Voltages.
The Voltmeter measures and displays the internal voltage selected by
N.
N=O
N=l
N=2
N=3
N=4
N=5
N=6
N=7
N=B
Ground. See Service Sheet
7.
Pre-Notch RMS/Average Detector with Ripple Filter. See Service Sheets
2
and
7.
DC Input Voltage without Filter. See Service Sheet
1.
Output RMS/Average/Quasi-peak Detector with Ripple Filter. See Service Sheets 6 and 7.
Output RMS/Average/Quasi-peak Detector. See Service Sheet
6.
Output RMS/Average/Quasi-peak Detector with SINAD Filter. See Service Sheets
6
and 7.
Notch Tune Voltage. See Service Sheet
4.
DC Input Voltage with Filter. See Service Sheet
1.
Input Range Detector. See Service Sheet
2.
NOTE
The
suffix
can also be two digits, XY. The difference (49.X SPCL
-
49.Y
SPCL) is then displayed. For example, 49.3 SPCL
or
49.30 SPCL gives a
display
of
the Output RMS/Average/Quasi-peak Detector with Ripple Filter
with respect to ground. 49.34 SPCL gives a display
of
the difference between
the Output RMS/Auerage/Quasi-peak Detector with Ripple Filter and the
same detector without the Ripple Filter.
50.N Display Oscillator Frequency.
The frequency of the Oscillator
is
displayed in the left display in all
measurement modes except dc level and where a valid measurement cannot be made. The right display operates
as usual. Resolution is the same as it would be
if
it
had been an input signal.
N=O Display frequency as normal.
N=
1
Display Oscillator frequency.
52.N Read Only Memory Verification.
The Controller displays the checksum of the read only memory (ROM)
specified by
N.
When specifying a ROM, use N=l through 10. The display is in the form: <actual checksum>
in the left display and <expected checksum> in the right display. Both displays should show
0
for ROM 10. See
Service Sheet 16.
Serial Prefix 2652A and Above:
ROM consolidation does not change this Verification.
53.N
Notch Filter Frequency Range.
Permits the frequency range of the Notch Filter to be displayed
or
manually
set.
If
no suffix is keyed in (that is,
53.
SPCL), the current Notch Filter range is displayed, where
0
is
the lowest
range and
3
is the highest. For N=O through
3,
the Notch Filter
is
set
to
the range specified by N. See Service
Sheet
3
and Special Function
54.N.
54.N
Notch Filter Coarse Tune.
Permits the coarse-tune code
of
the Notch Filter to be displayed
or
manually
set.
If
no suffix is keyed in (that
is,
54.
SPCL), the current Notch Filter coarse-tune code is displayed, where
0
8-12
rev.20JUN87
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