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OPERATING
INSTRUCTIONS
INSTRUCTION
MANUAL
Digital Mullimeter
Models
172A. 173A
I
L
TABLE 3-9.
General
Characteristics
of
Model
1722 Digital
Interface.
)IGITAL
OUTPUTS:
Logic:
BCD (8421)
Open-collector
positive
true
unless
otherwise
specified.
Data:
4 full
digits,
I partial
digit
(0,
1, 2, 3) and exponential
range
code
Function:
4-bit
code
(Q, AC VOLTS,
AMPS)
Polarity:
HIGH E +.
Overflow:
LOW 5 >
29999.
dutorange:
LOW = range
change.
Automode:
HIGH E
autorange
mode.
:LAG (m):
HIGH (logic
"0"
Z no output
change
occuring.
Logic
Levels:
HIGH Z open
collector
to output
LO.
LOW : closure
to output
LO.
Output
device
(2N5134)
greater
than
2OV breakdown,
<0.5V
at
5mA sink
(3TTL
loads).
Internal
pull-up
resistors
may be installed
on these
open
collector
outputs.
4.7K
minimum
value
is
recommended
when
"sing
internal
5 volt
power
supply.
IUTPUT TIMING:
Data
is updated
typically
every
320 msec
(non-trigger
mode).
Update
time
is
typically
1.2 msec.
Data
will
appear
at
an output
only
if
its
respective
strobe
is active.
The
FLAG will
go low
(Logic
"0")
typically
2 msec before
update
and
go high
typically
100 vsec
after
update.
Data
can be expected
to be unchanging
so
long
as the
flag
is
high.
If
FLAG RESET is activated,
the
FLAG will
reset
(go
to Logic
"0")
until
the
end of
the
next
data
update.
:EMOTE CONTROLS:
Strobe:
Strobe
lines
permit
word
serializing
in 4-bit
increments
or multiples
thereof.
HIGH inhibits
controlled
output
lines
from
conduction,
LOW enables
conduction.
Range
In:
4-bit
exponential
code.
L&
Range:
Low enables
remote
ranging
as set
by Range code.
Hold:
LOW inhibits
display
update,
output
update
and autorange
(A/O
continues
conversions).
Printer
Hold:
Same a5 hold
but
grouped
with
outputs
for
convenience
in
interfacing
printer.
Trigger
Mode:
LOW enables
TRIGGER control.
Trigger
Mode Disable:
LOW disables
TRIGGER.
Trigger:
LOW to HIGH transition
initiates
a new A/O conversion.
Flag
Reset:
LOW Set5
FLAG (FLAG)
t0
Low (HIGH).
Control
Logic
Levels
G Source
Requirements:
HIGH : either
an open
circuit
or a
voltage
between
c2.4V
and
5V referred
to output
LO.
LOW : closure
to OUtpUt
LO
within
0.8~
while
sinking
+1.6
milliamperes
(ITTL
load).
When TRIGGER MODE, HOLD
and LOAD RANGE code
bits
are
all
HIGH (inactive)
the
172A/173A
is
under
Front
panel
control.
These
REMOTE CONTROL inputs
have
priority
and will
override
any
front
panel
setting
once
activated.
SOLATION:
All
digital
outputs
and
remote
controls
are
isolated
from
172A/173A
analog
input
by
IO3 R and 5OOpF,
1200 VOC, IOOOV rrns AC maximum.
All
digital
outputs
and
remote
controls
are
isolated
from
chassis
ground
by
I06
Q and O.OluF;
250V TRY maximum.
1
3-20
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