Model 8903B Service
fault is removed. For example,
if
you key in 0.700 SPCL then increase the input signal level until an overload
condition is reached, you will find that the displays show
0000
0000
continuously except for the instant the overload
is detected (when the displays momentarily blink
0001
0000).
An automatic resetting of the input circuits removes
the overload as soon as
it
is
detected
so
the overload is observed only for one period
of
the Direct Control Special
finction cycle.
8-23.
Service Special Functions (Prefix 40-99)
The Service Special Functions are used
to
perform a variety of tasks related
to
service. The functions are cataloged
below. A suffix N indicates that
a
parameter other than
0
may be required
to
complete the Special Function Code.
See Table 8-1
for
entry
of
hexadecimal suffixes.
40.0 Controller Reset.
Initializes the Controller
to
its
power-up
state.
Because this disturbs the HP-IB hardware,
it is unavailable from HP-IB (gives Error 24). The power-up sequence is discussed in paragraph 8-27.
41.0 Controller Clear.
Initializes the Controller
to
its power-up state but bypasses the operational checks (see
paragraph 8-27). Leaves HP-IB hardware unaffected but clears any service request message (SRQ) being issued by
the Audio Analyzer, sets the service request condition
to
its
power-up state, and clears all bits in the status byte.
42.0 Display Software Date.
Displays the
date
of the sohare in the form: <month of year>.<day
of
month>
in the left display and <year> in the right display.
43.N Service Error Display Control.
Service Errors are numbered 65
to
95.
Refer to paragraph 8-26.
N=O Disables display
of
Service
Errors.
N=l Enables display of Service
Errors.
N=65 to N=95 quad Enables display of only the Service Error specified by
N.
Operating and Entry Errors
remain enabled.
44.N Notch Filter Mode Select.
Permits manual selection of one of three configurations of the Notch Filter.
N=O Notch Filter mode selected automatically as required by the measurement mode.
N=l Notch Filter in notch mode.
N=2 Notch Filter in flat mode.
N=3 Notch Filter in bandpass mode.
45.N
SINAD
Meter Enable.
Permits the SINAD meter to be enabled for measurement modes other than SINAD
and, in the SINAD mode, for measurements greater than 24
dB.
It
is most often useful for reading distortion
when the displayed reading
is
very noisy. When this Special Function
is
invoked, the meter reads the ratio
of
the level at the Pre-Notch RMS/Average Detector to the Output RMS/Average/Quasi-peak Detector, expressed
in
dB.
The reading must, therefore, be interpreted relative
to
the
dB
reading in the right display. Usually, this
entails ignoring the minus sign and subtracting multiples of 20
dB.
For example,
a
distortion reading of -66.80
dB
in the right display may be indicated
as
6.8
dl3
on the SINAD meter
or
-76.80
dB
may be indicated as 16.8
dB.
AC level readings will normally be
0
dB.
N=O SINAD meter enabled normally. See
Detailed Operating Instructions
in Section 3.
N=l SINAD meter enabled in all measurement modes except dc level.
46.N Count Internal Signals.
The Counter counts the internal signal selected by N and displays the count. The
resolution is the same as would normally be displayed.
N=O Oscillator Frequency. See Service Sheets
9
and 13.
N=l Input Frequency. See Service Sheets
2
and 13.
N=3
Output Amplifier Frequency. See Service Sheets
5
and
13.
reu.2OJUN87
8-11
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