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Tektronix 213 DMM User Manual

Tektronix 213 DMM
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segment
digital
display
character
8.
Internal
blanking
sig-
nals
form
the
plus
or
minus
sign
and
the
decimal
point.
To
form
each
of
the
digital
display
characters
0
through
9,
the
Character
Generator
converts
the
serial BCD
data
from
pins
10,
11,
12,
and
13
of
U260
into
Z-Axis (or blanking)
Out-
put
signals.
The
Z-Axis signals
blank
one
or
more
of
the
segments
of
the
character
8
to
form
the
other
characters.
The
current
through
0278,
which
is
gated
by
0275
and
set
by
S120
contacts
5 and
6,
causes
the
decimal
point
to
be
positioned
properly
on
the
crt.
Table
9-2
shows
the
relationship
between
one
displayed
character
and
the
BCD
output
of
U260.
The
BCD
data
consists
of
four
groups
of
BCD
data
(one
group
for
each
character);
therefore,
this
relationship
can
be
measured
(with
a
voltmeter)
only
when
one
of
the
four
characters
is
the
number
to
be
measured
and
the
other
three
charac-
ters
are O's.
Figure 3-5
shows
the
relationship
between
one
displayed
character
and
the
Z-Axis
Output
from
U270.
This
output,
like
the
BCD
data,
is
repeated
four
times
(once
for
each
character)
and
can
be
measured
(with an oscilloscope)
only
when
one
of
the
four
characters
is
the
number
to
be mea-
sured
and
the
other
three
characters
are O's.
Polarity
Sign
Control
The
voltage
at
pin
14
of
U270
controls
the
sign
on
the
dis-
play.
Approximately
0.7
volts negative causes a positive
sign,
while
about
0.7
volts positive causes a negative sign.
A positive 6 volts will
turn
the
sign
off.
In
therms
mode
of
operation
when
RMS
pushbutton
S185
is
selected,
a positive
6.5
volts
is
applied
through
R267
and
turns
the
sign
off.
In
the
ohms
mode
of
operation,
S160
applies
a
current
to
the
base
of
0182
which
causes
it
to
saturate
and
apply
a
positive
6.5
volts
through
R267,
again
turning
the
sign
off.
In
the
Gm
Converter
a positive
input
causes a negative
0.7
volts
to
appear
at
pin 6
of
U
186,
which
causes a positive
sign. A negative
input
causes a positive
0.7
volts
to
appear
at
pin 6,
which
causes a negative sign.
Overrange Circuitry
For
the
following
description,
refer
to
the
Overrange Cir-
cuitry
Simplified
Schematic
Diagram,
Fig. 3-6,
and
the
Overrange
Timing
Diagram, Fig. 3-7.
The
overrange
indication,
that
appears
on
the
readout
dis-
play
as
scrambled
character
segments
or
8's,
is
caused
by
a
negative
unblanking
signal
at
the
input
to
the
Z-Axis Am-
plifier
0390,
which
prevents
blanking
of
the
unused
char-
@
Theory
of
Operation-213
Service
DISPLAYED
CHARACTER
2
3
4
5
Z-AXIS
OUTPUT
I
I
6
________
h
..
l
___
_
7
8
I
I
I
9
n
I
I
I
I
I
0
n I
t
+
REFERENCE
REFERENCE
(BLANKING
(BLANKING
SPIKE
SPIKE
BETWEEN
BETWEEN
CHARACTERS)
CHARACTERS)
j
..
7
DIVISIONS
..
,
HORIZONTAL
DEFLECTION
Set
INPUT
COUPLING
to
GND
for
O character
verification
(display
is
all zeros).
For
pattern
verification,
sync test
oscilloscope on
pin
2,
U270
and insure all characters
except
verification
character is a 0.
1481-31
Fig.
3-5.
Character Generator 2-axis
output.
3-7

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Tektronix 213 DMM Specifications

General IconGeneral
BrandTektronix
Model213 DMM
CategoryTest Equipment
LanguageEnglish

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