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INSTRUCTION
MANUAL
Digital Multimeter
Models 172A. 173A
e.
Detailed
Explanation
of
Model
1722.
TRIGGER MODE AND TRIGGER:
(See Schematic
28248E)
HOLD:
LOAD RANGE:
REMOTE CONTROLS:
TRIGGER MODE DISABLE:
(See Schematic
282490)
OPERATING
INSTRUCTIONS
When TRIGGER MODE is active
(Low),
output
data
and dis-
play
will
not
be updated.
TRIGGER MODE enables
TRIGGER.
Conversion
starts
within
1.6
milliseconds
after
TRIGGER.
Integration
starts
120 milliseconds
after
start
of
conversion.
If
either
HOLD or
PRINTER HOLD is
low
the
output
data
and
the
display
will
not
be updated
and
the
FLAG will
stay
at
HIGH (unless
reset
by FLAG RESET).
When LOAD RANGE is
low
the
172A/l73A
will
go to
the
range
as set
by the
RANGE IN code
(Table
3-10)
at
the
beginn-
ing
of
the
next
conversion.
As long
as LOAD RANGE is
held
low,each
instrument
will
remain
on its
programned
range
overriding
front
panel
UPRANGE, DOWNRANGE and
AUTORANGE.
RANGE IN codes
programmed
outside
the
limits
of Table
3-10
will
result
in
the
nearest
valid
ranqe
to that
programmed.
LOAD RANGE will
always
cause
a DMM
range
change.
However,
the
display
and output
data
will
be held
(not
updated)
during
TRIGGER MODE or HOLD.
Referring
to
timing
schematic
28249D.it
is possible
to
just
miss
a REMOTE CONTROL update
prior
to data
output.
This
can be misleading,especially
in
the
case
of
HOLD.
A HOLD just
missed
(unknown
to
the
user),
just
before
data
begins
to change,could
result
in erroneous
data.
To check
if
this
occurred,
it
is suggested
that
the
FLAG be examined
no sooner
than
IO usec
after
activation
of
the
HOLD bit.
If
flag
is
low wait
until
it
goes
to
HIGH before
expecting
the
HOLD bit
to have
been
accepted.
Other
REMOTE CONTROL bits
such
as TRIGGER MODE and
TRIGGER,
LOAD RANGE and the
RANGE IN code
can be kept
active
for
longer
than
an output
data
update
time,
i.e.
>3.2
msec to
insure
proper
REMOTE CONTROL acceptance.
When in TRIGGER MODE and triggering
into
an autoranging
condition,
normal
operation
will
give
an output
for
each
range
encountered
during
the
autorange.
However,
if
this
is undesirable
the
AUTORANGED output
bit
can be
tied
to TRIGGER MODE DISABLE
and FLAG RESET.
This
will
prevent
the
FLAG from
being
set
and
ignore
further
triggering
until
the
final
range
is
reached.
3-21
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