User`s guide

16
6. Start the measurement
(Sweep menu): to invoke a
measurement, press the
MEASURE key. At any time
during the acquisition of
data, the ABORT key can be
pressed to stop the
measurement. It may take a
few seconds before anything
happens because the abort is
processed after the current
trace acquisition is completed.
If the instrument appears to
be frozen after pressing
ABORT, press INSTR PRESET
followed by the USER key to
return to the personality.
If the top trace does not show
a signal during a
measurement, check that the
stop, start, and step
frequencies, and N and M are
correctly set. As the program
steps along, the IF frequency
and delta phase of the point
being measured is shown on
the display.
7. Normalize and scale the results
(Process menu): if the
measured trace is to be used
as a reference for
normalization, then press the
NORMALZ softkey (see the
previous discussion about
normalization on page 9).
The normal ON/OFF key is
used to turn normalization on
or off. The trace definitions
will change according to the
status of this softkey (e.g.,
MEM1 for an unnormalized
trace, and MEM1-MEM3 for
a normalized trace).
The AUTO-SCALE softkey is
used to automatically scale
the traces to fit the screen. If
a phase trace is displayed,
then the electrical length is
automatically subtracted to
show deviation from linear
phase. This auto-delay
routine uses the entire phase
trace to do a least-squares fit
to a straight line. If it is
desired to flatten out a
smaller portion of the phase
trace, such as the center of
the passband of a filter, then
the auto-delay routine must
be done in conjunction with
markers. The markers should
be placed on trace 2 to define
the frequency band of interest.
The auto-delay routine can
then be invoked again by
pressing AUTO-SCALE. This
routine can also be done via
the MENU keys by pressing
AUTO DELAY under the
Scale menu (more 2 of 2).
All of the traces can be
manually scaled or offset if
desired by using the
appropriate keys under the
Scale menu (more 1 of 2).
Printing/Plotting the
Results
An HP-IB printer or plotter is
needed to directly obtain a
hardcopy of the traces. It should
be connected to the HP-IB
connector of the HP 70004A
display/mainframe, and NOT to
the HP-IB connector on the
HP 70820A module. Make sure
that the HP-IB switch on the rear
panel of the display/mainframe
is set to the on (up) position.
Non-HP-IB printers such as
LaserJets and DeskJets can be
used with an HP-IB to
Centronics converter, such as
the HP 92203J/K.
The PRINT or PLOT keys on the
display/mainframe are used to
dump the traces to the printer
or plotter. Hardcopy parameters
such as printer type, and the
address of the print or plot
device are set under the
Hard Copy menu of the
DISPLAY keys. When using an
HP-IB to Centronics converter,
select either the THINK JET or
the PAINTJT BLACK printer
driver. Do not press any keys on
the display until the printout is
complete — otherwise, the
printout will be aborted.
If the program was loaded into
the memory of the HP 71500A
via a memory card or external
disk, and no computer is
connected to the
display/mainframe HP-IB
connector, then the PRINT and
PLOT keys on the
display/mainframe work
properly. If an external
computer was used to download
the program to the HP 71500A
and it is still connected to the
HP-IB bus, then it either must
be physically removed from the
bus, or it must relinquish bus
control to allow the
display/mainframe to control
the printer or plotter. To remove
the computer as a bus
controller, type the following
BASIC commands in the
computer:
LOCAL 7
SEND 7; UNT UNL DATA
Now press the appropriate key
on the display/mainframe to
initiate a print or plot.