Racal Instruments 9901 Maintenance Manual page 22

CHAPTER
1
GENERAL
DESCRIPTION
INTRODUCTION
1
.1
The
9901
is
a six-digit
auto ranging
universal
counter
timer,
powered
from a.c.
mains and
providing a
comprehensive range
of facilities.
The
heart of the
instrument
is
a large scale integration
element
(IC2)
which
performs
all
the
measuring
functions of
a
50
MHz
universal
counter
timer.
This integrated circuit will
commonly
be
referred to as the
'CDI Chip'.
OPERATING
FACILITIES
1.2 (a)
Frequency measurement
ranges:
AC
coupled: 10
Hz
to
50
MHz.
DC
coupled:
DC
to
10
MHz.
In
AUTO
mode
the instrument automatically
selects
the gate time
(.01, 0.1 or
Is)
which
gives
optimum
resolution
on
the display.
5
(b)
Period
measurement,
1
to
10
periods
in
decade
steps,
a.c.
ord.c.
coupled.
(c)
Ratio
measurement.
(d)
Time
Interval, single or
double
line,
with
manual
or electrical start/stop
signals, trigger
slope selection
and choice of pulse or contact timing
control
.
(e)
Time
Interval
average,
single or
double
line,
with
trigger
slope selection
and
choice of pulse or contact timing control
.
(f)
Totalize, with electronic or
manual
start/stop.
In
addition, other control
facilities
provide
AC/DC
input selection,
manual
hold
and
reset,
and
self
check.
POWER
SUPPLY
1
.3
The
instrument operates from a.c. supplies
between
94V
and 265V, 45
to
450 Hz.
A
tapping
and
link
on the internal
mains
transformer
must be
correctly set
according
to the
user's
supply voltage,
as
described
in
Chapter
5.
A
label fixed to the rear
panel should indicate the selected range. Spare
labels
are supplied with the instrument
for
voltage ranges other than
223V
to
251V.
9901 Vol.
2
1-1