1 – 8
Getting Started
When the TTL input is low (asserted), the shutter is commanded to
be in the
Normal
state.
Pressing either [
] (reset), [OPEN], or [CLOSE] are requests for man-
ual control that will force the instrument out of
EXT LVL
mode and
back to the
INT TRIG
mode.
The [
] (trigger) key has no e
ff
ect while in
external level mode
.
1.2.4
Timing and sequences
The SR470 is capable of controlling an attached shutter head through
timed sequences of operation, including triggered bursts.
Sequences are allowed when the shutter is powered on and the SR470
is in the
INT TRIG
or
EXT TRIG
operating mode (
§
1.2.3). The se-
quence does not begin until a trigger is received; the trigger source
may be the front panel [
] (trigger) key, the rear-panel TTL control
input (if in
EXT TRIG
mode), or a trigger command from one of the
remote interfaces.
The front panel
TRIGGER
indicator, located next to the [
] key,
remains illuminated for the duration that any timed sequence is in
progress.
1.2.4.1 Timing diagram
The timing diagram for the instrument appears on the front panel
and is reproduced here:
Figure 1.2: Timing diagram.
The sequence represents a single exposure cycle, with a
predelay
T
pre
,
exposure
of length T
exp
, and
postdelay
T
post
. The length of
these intervals combined is T
total
, the total duration of the sequence.
There are two curves drawn on the timing diagram, one for
normally
open
operation (
§
1.2.2.2) and one for a
normally closed
operation;
the curves are labeled by designations
N.O.
and
N.C.
.
Suppose that the shutter is idle in its
normal
state, (and in the
INT
TRIG
or
EXT TRIG
mode) when a new trigger signal is received. The
timed sequence begins when the trigger is received. During the first
part of the sequence, the
predelay
, the shutter remains in its
normal
SR470 Shutter Controller
