1.2 Front-Panel Operation
1 – 9
state. At the end of the
predelay
, the
exposure
time begins. As
illustrated on the timing diagram, the
exposure
is defined to begin
at the moment that the shutter begins moving from the
normal
to
the
Normal
(
asserted
) state. The shutter remains commanded to
the asserted state until the end of the
exposure
time. The
postdelay
follows the
exposure
, and is defined to begin at the moment that the
shutter head begins to return to the
normal
state. The SR470 is able
to accept new triggers after the end of the postdelay.
As a concrete example, consider the case with a shutter that has a
fixed opening
/
closing time of 10 ms, configured in
normally closed
mode, with pre-delay of 500 ms, exposure of 50 ms, and postdelay
of 10 s. Further suppose that the shutter is in the closed state when
a trigger is received. 500 ms after the trigger is received, the shutter
begins to open, and is fully opened 510 ms after the trigger. Since the
exposure time is 50 ms, the shutter begins to close at 550 ms after the
trigger, and is fully closed 10 ms later. The
postdelay
of 10 s begins
at the moment that the shutter begins to close, and finishes at a time
10.550 s after the trigger was received.
The actual opening
/
closing time of a shutter is hardware and possibly
mode dependent; please consult the user manual for your shutter
head.
1.2.4.2 Entering timing parameters
Timing parameters on the SR470 can be configured and viewed by
using the three keys in the “Timing” section of the front panel in
conjunction with numeric controls in the “Modify” section of the
front panel.
The [Tpre
/
Tpost] key allows the operator to view and edit the
pre-
delay
and
postdelay
. Pressing this key alternates between selecting
those two delays, and indicator lights to the left of the numeric dis-
play indicate which of the two delays is shown.
The [Texp] key and the [T Total] key allow the operator to view
and edit the
exposure
time and total duration of the sequence. The
“frequency”
f
of the full cycle is defined as
f
=
1
/
T
total
, and may be
accessed by selecting [Shift][Frequency]. For each of these selections,
the appropriate indicator “Texp,” “Ttotal,” or “Freq.” is illuminated
to the left of the numeric display when that parameter is displayed.
If the sequence timing has been entered as a set of delays (measured
in seconds), then it is important to note that the frequency shown
in hertz on the numeric display may be truncated, since the true
frequency is equal to 1
/
T
total
and may have trailing digits that do not
fit on the display. As an example, if a timed sequence were set up with
SR470 Shutter Controller
