User Gate Function - Keithley 775A Instruction Manual

NOTE
To prevent operator
error,
there
is
an
internal
alarm
that
beeps
whenever
a limit
is
reached,
(e.g. lOOfisec
low
limit or lOsec
high
limit),
With
the
GATE/DELAY
light
on, the alarm
will
sound
W'hen
the users gate
is
displayed
and
the
A
but-
ton
is
pressed. Refer
to
Table 2-2
alarm
conditions,
2.6,3
User Gate Function
The
user gate function
is
useful
when
a,
gate time other
than
the
predetermined
gate times
listed in Table 2-1
is
re-
quired.
The
limits
which must
be observed
are the
minim,
um
limit
of
jj30/isec
and
the
maximum
limit of lOsec,
The
user
gate function
is
accessible
m
the
FREQ
A,
B
and
C
and
Period
Averaged
functions.
To
operate the
instru-
ment
in
the user gate
mode
proceed
as follows;
1,
Press the
GATE/DELAY
button
and
observ^e
that the
light
turns
on and
the instrument displays the following
message:
GAtE
DDD+D
SEC
Tnis
display
shows
the actual
gate
time
that
the
instru-
rnent
is
set to operate.
DDD±D
SEC may
be any time
from
lOOE-6
to
lOE+0.
2,
Press
and
hold
in
the
GATE/DELAY TIME
A
button and
observe
that the display increments,
.After the lOsec gate
time
the
instrument
will
enter the user gate
mode
and
the instrument
will display the I'oUowing:
%-
USEr
GATE SEC
rYessing
the
A
button
after
the gate
is
displayed
will
sound an
alarm.
3,
the
GATE/DELAY
button.
The
light will
turn
off
and
the instrument
will
be ready
for
measurements
with
an external gate time.
4,
Apply
a
TTL
pulse
to the rear
panel
EXT
ARMING
k
GATE/DELAY
BNC
terminal.
The
high
level
of the
TTL
pulse width determines the length
of the gate time.
NOTE
The
user gate function
may
be accessed
only
when
the
GATH/DELAY
light
Is
on.
To
exit the
user gate function press the
GATE/DELAY
TIME
^
button. Of
both
the
A
and
^
buttons
to
preset
the gate
time
to Isec.
The Model
773 has
a
delay function which
disables the
closure of
the
opened
gate for the predetermined periods
listed in
Table 24. This
function
is
very
useful
in
burst
measurements,
relay open/close time
measurement,
s
where
houncG
time should be elimmated
or
in
measurements
done on
a train of pulses.
NOTE
The
delay
mode
is
accessible only
when PERIOD
A,
TIME A
—
B or
PLS
A
functions are on. The
.selection of
any other
function,
when
the
DELAY
light
is
on,
will
cause
the instrument
to
e.xit
from
delay
mode.
The
delay time
may
be
selected as follows:
1.
Press the
GATE/DELAY
button.
The GATE/DELAY
iighl:
will
turn on and
the
instrument
will display the follow-
ing mesvsage;
dELAY
DDD±D
SEC
2-
To change the delay
time,
press the
GaTE/DEL
> >
-4
or button.
When
the
A
or button
is
de
for
more
than
one
second,
the instrument w|U
or
decrement
continuously.
3.
Pressing the
A
and
T
buttons
simuitaneou.slv
will
change
the delay time
to a
preset value
of Isec.
4.
To
resume
norinal display
operation,
press the
GATE/DELAY
button.
The GATE/DELAY
light wili
turn
off
and
instrument
will be ready
to
perform measure-
men?
with the newly
selected delay time. Table
2-1
Irst--
the gate/delay times which
arc
available as
presdected
values,
I't
is
also
possible
(o
change
the delay time
w!.th<.n.d .obser-
ving the
actual
delay time
on
the
display.
To do
so.
simph,'
press
the
GATE/DELAY TIME
A
or'
'f'
button,
l.hum,
time
the
A
button
is
pre.ssed, the instrument
will
mcrvnu'n:
one
delay time.
Each
time the
button
i.s
pres.sed, the
instrument
will
decrement one
delay
time.
When
A
or
T
button
is
held
in for
more
than one
second, the
instru-
ment
wili
increment
{or
decrement)
after
each measuring
cycle.