Operation Section 3
3-1
SECTION III
OPERATION
3-1. INTRODUCTION.
3-2. This section contains the operating instructions for
the Model 1121A Audio Analyzer.
3-3. OPERATING CONTROLS, INDICATORS AND
CONNECTIONS.
3-4. The controls, indicators and connectors used during
the operation of the instrument are listed in Table 3-1 and
shown in Figures 3-1 and 3-2.
3-5. OPERATING INSTRUCTIONS.
3-6. The operating instructions for the Model 1121A are
divided into sections of Initial Conditions, Local Operation
and Remote Operation.
3-7. INITIAL CONDITIONS.
3-8. Initialize the instrument as follows:
a. Connect the power cord to the instrument and to
the desired power source. Refer to paragraph 2-7 for
proper power application.
b. Set the front panel power switch to ON.
c. Depress the LCL/INIT key.
d. The SOURCE display will contain the instrument
firmware identification number and the other displays will
contain dashes for a period of about two seconds. The
SOURCE display will then contain 1000.00 Hz with the
KYBD legend illuminated and the ANALYZER display
will change to contain the message for one level
measurement cycle.
3-9. LOCAL OPERATION.
3-10. Function Selection. The DATA ENTRY keypad is
common to all functions of the Model 1121A. The KYBD
legend determines the active display window to which the
DATA ENTRY keypad is dedicated at any given time. To
select a function simply depress the function key desired.
The results will be the LED of the function key will be
illuminated, the current value of the selected function will
be displayed in the window above the key, and the KYBD
legend will be illuminated in the display window. The
DATA ENTRY keypad is dedicated to the selected
function and any unit selection or number entry
will appear in the active display window. When selecting
measurement functions the message may appear
to indicate that a measurement cannot be displayed
instantly for any of five possible reasons:
1. The first measurement cycle is in progress and
cannot be displayed.
2. The measurements’ minimum signal require-
ments are not met, for example, frequency measure-
ments cannot be made if the input level is too low.
3. The input level is overrange.
4. The input signal is changing faster than the
analyzer can respond.
5. The notch filter is in the process of being tuned to
the fundament frequency in the distortion or SINAD
modes.
3-11. Data Entry Operation. Once a function has been
selected, new values may be entered with the DATA
ENTRY keypad. To enter data simply depress the
desired digit keys followed by the appropriate unit key or
ENTER key. During digit selection a (‘) mark will
appear in the display to the left of the first digit selected
to indicate the number in the display is in the process of
being entered. No action is taken until the unit or EN-
TER key is depressed. The unit keys can also be used
aside from number entry to select display modes. For
example, to change the level measurement displayed in
mV to logarithmic units in dBV, simply select the analyzer
LEVEL key and depress the dB key in the DATA ENTRY
keypad. The display program will calculate and display
the logarithmic value. The ENTER key serves a dual
function as a dimensionless unit key for SPCL, ADRS,
and PRGM number entry and also as a default
unit terminator of V, %, and Hz for functions where more
than one unit can be selected.
3-12. Many of the Model 1121A functions have multiple
display and entry modes. Listed in Table 3-2, Function
Display And Data Entry Units, are the display legends
which can be active for each function along with the unit
keys in the DATA ENTRY keypad which select the avail-
able display modes. Argument entry ranges for all the
Model 1121A functions are described in Table 3-3, Valid
Function Argument Range. Number entry out of range of
the selected functions will result in an error displayed in
the SOURCE display window. Errors can be cleared by
depressing any key. If at any time prior to entry a wrong
digit is entered, depress the CLR key to clear and restore
the previous display.
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