Philips PM2517E - Decimal Point; Polarity and Unit Indication; Serial Display

38
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fn this
circuit the RC time
is determined
bv C 701 and
R 721. C
701 is connected
to
+8.5
V and
R 721 is
connected
to signal
DS
1.
(DS
1
=
500 Hz and switching
between
0 V and
-
8.5
V). The resulting voltage
on
R 721 will be due to the
resistor and capacitor
about
4 V. The
RC time. together
with the switching
point
of the
FET
V 705
will result in a time
of about
40 sec. In case
of sTAND
BY, logic
0
(-8.5
V) will be
connected
to input BL
of the display
unit via
R 720 which
means blanked
display.
When
push
button
D ISPLAY is depressed, C
701 is discharged,
FET
V 705 starts conducting,
causing
transistor
V 706 to conduct,
which
gives
a logic
1 ro the BL input
which means
thar the display
is not blanked.
After
40
sec.
FET
V 705
switches
again and the
circuit is
in
its
rest
position
again.
3.3.5.4.
Serial displav
(D51,
DS2, DS
=
Digit Select)
Signals
DS1 and D52 are supplied
to the
dual
1
of
4 decoder D
702
{see
timing
diagram,
Fig
25)
The decoded signals
switch the
relevant LED's
in the order
102,103.
tO0 and
101 .
ln case of overrange
(indication
> 9999
=
OO0O)
signal OVR
is true
(logic
1) and
one
part
ol the
dual I of 4
deco.ier
HEF 4555 is blocked
(No
enable).In this
case only
LED 102 is
ignited asthis
one
is switched
via
the other
part
of
the HEF 4555
(enable)
3.3.5.6. Decimal
point
lDP3,
DP2,
DPI)
The decimal
point
information is directly
derived from the
OO 0055
lD
703/14/151161
and
is supplied
to the
corresponding
decimal
points
via
a
270 Q resistor
(see
table and
OO 0055
specification,
chapter
3.3.5
3.).
Ranqe DPI
DP2 DP3
9.999
99.99
999.9
1
0
0
0
1
0
0
0
1
3.3.5.7.
Polaritv and unit indication
Unit indication
The unit
indication is made
with
the
combination
of LED's and the
position
of the
function
selector switch
S1
.
When
no
LED
is lighted the
position
of
the function selector
determines
the unit
indication e.g.
function
kQ
and
no LED indication
(O
or
lVlQ
)
means range
kQ
(see
table below).
Function
Signal
OO 0055
Switches
LED
lighted lnd
ication
m
v.\,/v...(6,5)
v.v/v...(6,5)
ks2
I\,1, R NG
C
RNG C
kst
KQ
kr)
rvfl
NUro
....
tlls2
.... a
kf2
+
-60...+2oo
oc
(m)
A-
(m)
A'v
Polarity
indication
(+
or
-)
The
polarity
is indicated
by means
oi LED's.
The information
for
the
LED's is directly derived
from
the
OO
0055
(D
703/18/19).
3.3.5.8. OVR
(overrange)
In case of overrange
signal OVR becomes logic 1 causing
digits
103,
101 ana
100 to
be blanked'
Only digit'l02 is lighted.
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