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1.10
HOLD
1.10.1
The
Hold
feature
allows
readings
to
be
held
indefinitely,
A
new
measurement
cycle
is
initiated
using the
RESET
key.
1.11
GATE
TIME
AND
RESOLUTION
1.11.1
Refer
to
Subsections
3.4.3
and
3.4.4 for details.
In
Frequency
A
and
B,
Frequency
C, Period A,
Ratio
A/B
and
C/B
modes, a gate time
may
be
specified
from
the
front
panel
(Gate
Time
mode)
or
by
the
selected
display
resolution
using
the
RESOLUTION
(H)
keys (Resolution mode).
The
available
gate
time
range
is
1
ms
to
99.9
s.
1.11.2
In
the Total
A
by
B and Manual
Totalize
modes,
the
counting
interval
(i.e.,
gate time)
is
controlled
by
the
time
interval
between
the
start
and
stop
signals at Input
B, or
between
successive operations of the
HOLD
key.
1.11.3
In
Phase
mode,
the
gate
time
is
fixed
and
the
display resolution
is
determined by
the input signal frequency.
1.12
EXTERNAL FREQUENCY STANDARD
INPUT
1.12.1
The
1994
may
be operated
using
an external frequency standard.
The
counter
will
operate
from
the external
standard
when
a
signal
of
sufficient
amplitude
is
applied at
the
EXT
STD INPUT
BNC
connector.
The
counter reverts
to
internal
frequency standard operation automatically
if
the external
standard input
is
removed.
1.13
STANDBY
MODE
1.13.1
When
the
1994
is
switched
to
Standby, the
internal
frequency standard
continues
to
operate but the measuring
circuits
are switched
off.
1.14
GPEB
INTERFACE
1.14.1
An
IEEE-488-1978
GPIB
interface
is
standard on
the
1994.
This feature
permits
remote
control of
all
the instrument's functions
except
the
power
ON/OFF
and
STBY
switching. See Section
4 for
1994 system
operation.
1.15
OPTIONS AVAILABLE
1.15.1
Rear
Panel
Input (Option 01)
1.15.1.1
This permits use of
rear-mounted
Inputs
A,
B,
and C.
This
is
a
factory-
installed
option.
1.15.2
Frequency
Standards (Options
04A
and 04E)
1.15.2.1
Two
internal
frequency standard
options are available.
The
technical
specifications
are given
in
Table
1.1.
The
frequency standard
can be changed,
if
necessary,
by
the
customer
(see
Section
2).
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