4
In the numeric mode, the entire keypad is active.
Data may be entered as a floating point number
or in exponential notation. Entered data may be
edited by using the BSP (backspace) key.
Backspacing past the left edge of the screen will
cancel the command. The entered data is
actually used when the EXC (Execute) key is
pressed. Selecting another menu item will have
the same affect as pressing the EXC key.
Error messages will appear on the LCD to
indicate improper commands. For example, an
attempt to decrement a delay below zero will
generate the error message "Delay Range Error".
The error message may be cleared from the
LCD by pressing any key.
TRIGGER MENU
The "top" line on the trigger menu is:
Int Ext SS Bur Line
The cursor, underlines one of the five modes in
the list to indicate Internal, External, Single-
Shot, Burst, or Line trigger. The left and right
cursor keys may be used to change the mode.
Subsequent menus, which are different for each
trigger mode, are selected by pressing the TRIG
menu key again.
TRIGGER SUBMENUS
Mode
Menu Example
Int
Rate =10000.000Hz
Ext
Threshold =+1.00V
Slope(±) = +
Trigger Term = HighZ
SS
Single-Shot (Exc)
Bur
Rate =10000.000Hz
Pulses/Burst
10
Periods/Burst
20
Line
(No submenu)
The Internal trigger mode has only one submenu
to set the trigger rate. The rate may be entered in
the numeric mode or modified in the cursor
mode. Only four digits of precision are allowed,
and digits more than three places beyond the
decimal point will be truncated.
The External trigger mode has three submenus to
specify the threshold, slope and termination
impedance of the external trigger input. Each
submenu is selected by pressing the TRIG key. The
Threshold may be entered as a floating point number
or may be modified in the cursor mode. The Slope
may be selected by using the cursor (up/down) keys,
as can the Trigger termination impedance. The
threshold, slope, and termination impedance shown
in the example menus would be appropriate for
triggering on the rising edge of a TTL Pulse.
The Single-Shot trigger mode has only one
submenu. If SS is selected by the cursor, pressing
the TRIG menu key will display "Single Shot
(EXC)." Now each press of the execute key will
trigger the timing cycle.
The Burst mode has three submenus to specify
trigger rate, number of pulses per burst, and number
of periods between the start of each burst of pulses.
All of the items may be entered in the numeric
mode, or modified in the cursor mode. The Rate
may be entered in floating point or exponential
notation, and may be specified to four digits of
precision. For the entries shown in the above menu
example, there would be 10 pulses per burst, each
pulse separated by 100 µs, and a new burst of pulses
would start every 20 periods, i.e. every 2 ms.
The Line trigger mode has no submenus. The unit
will be triggered on a zero crossing of the power line
at the line frequency. The line trigger is also
synchronized to the internal 80 MHz timebase, so
that the timing jitter of the delay outputs in this
trigger mode will be very low (typically 25 ps rms).
TRIGGER TRICKS
There are several techniques that may be used to
extend the versatility of the DG535's trigger modes.
The Jitter of the delay outputs will be reduced by
about a factor of two (to less than 25 ps rms) if the
unit is triggered synchronously with the 10 MHz
time base. This is done automatically if the Line
Trigger is selected. You may also want to arrange
your external trigger so that it is synchronous with
the 10 MHz output on the rear panel (if the internal
time base is being used).
