Table of Contents
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1.1
INTRODUCTiON
The
Keithley
Model
775
Programmable
Couhter/Timer
is
a
nine
digit,
microcomputer
based,
fully
programmable,
universal counter/timer.
The Model
775
measures
with
high
resolution the following
parameters:
®
Frequency
A
«
Frequency B
e
Frequency
C
s
Period
«
Period
Averaged
«
Time
Intervals
A —
B
«
Pulse
Width
(positive
or negative)
A
The Model
775 has
an
14mm
(0.56
in.)
LED
display.
The
display
consists of
9
digite
with an
additional
digit for ex*
ponent.
The
buEt-in
interface
makes
the
instrument
fully
programmable
over the
IEEE-488
bus.
The Model
775
contains
a
programmable
trigger
level
that
allows additional
flexibility
in
measurements
over the
bus
(e.g.
measuring
rise
and
fall
time with
trigger
points other
than
10% and ^%),
Gate
time
is
programmed
in
46 steps
from
lOO.ttsec
to
lOsec
or
external
from
the
front
panel
or
over the
bus.
1.2
MODEL
775
FEATURES
Dual
Channel
Capability— Dual channel
capability
with
two
similar
channels
up
to
TlOMHz.
Trigger
Delay
Channel B—This
feature
is
important
for
some
channel
A
B time
measurements,
True
DC
Coupling—Allows
the
Model
775
to
do channel
A
"*
B
naeasureinents.
Reciprocal
Techr\ique— This counting
method
provides ad-
vantages
over
all
traditional
counters
from
DC
up
to
the
dock
frequency
(lODMH?.)-
The
constant
relative
resoiu-
lion
(8
digits/second
independent
of
input frequencv)
makes
it
even
more
useful
for
low frequency
applkalions.
1.3
WARRANTY
INFORMATION
'Warranty
information
may
be found
on
the inside front
cover
of
this
manual. Should
it
become
necessary
to
exer-
cise
the
warranty
contact
your
Keithley representative or
the factory
to
determine
the
proper
course,
of
.action.
Keithley
Instruments
maintains
service
facilities
the
United
States,
United
Kingdom
and
throughout Europe,
Information concerning
the application, operation
or
.ser-
vice of
your instrument
may
be
directed
to
the applications
engineer
at
any
of
these
locations.
Check
the inside
rroni:
cover
for
addres,ses.
1.4
MANUAL ADDENDA
Information
concerning improvements
or change.?
to
the
instrument
which
occur
after
the printing
of
this
nunuiai
wdli
be found
on an
addendum
sheet
induded
with
this
manual
Be sure
to
review
these
changes
before
attemp-
ting
to
operate or
service the
insfrument.
Full
Programmability—
Full
programmability
of
all
func-
tions
and
modes
including
different
SRQ
masks and
chan-
nel
selection.
High
Frequency
Option—
HF-option
adds
a third
measure-
ment
channel
for
frequencies
up
to
IGHz,
High
Resolution—
A
lOOMHz
clock
rate,
along with
the
latest
technique
In
frequency counting
(reciprocal techni-
que),
provides the
high
resolution
of
8
digits.^second
or
iHz
out
of a
lOOMHz
input
signal.
1.5
SAFETY
SYMBOLS AND TERMS
The
following
safety
symbols
and
terms
are
used
in this
manual
or
found on
the
Model
775.
The
AiA
symbol on
the instrument
denotes
that
the
user
should
refer
to
the operating
instructions
in this
manual
Tlie
WARNING
used
in this
manual
explain?
danger?
that
could
result in
personal
injury
or death.
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