Philips PM2517X - 3.3.5. Display unit N2 (Fig.25 and 54); 3.3.5.1. General

36
(
l_,
t_
When
switched
on
in a multi-range
function,
the instrument
wlll
be set in
the manual ranqino
state.
Thtsalsooccurswhen,sswrtcheotromasingle-rangetunction(f
oC,
mA
-
o. -al
tioa.nultr
rarge
function
{V'.V
-:
.
kS-l).
I
In this
case
the kg input
of rhyristor
V150 is
activated
via the
function
switch
and R727.
The
thyristor
starts
conducting
and a logic
0
(-8,SV)
is
supplied
to the AUT input
of the
OO 0059.
which
means
manuat
rangtng.
To
get
out
of the manual
ranging
state
the AUT
switch must be
oepresseo.
In
the functions
(m)
A . . .
,
{m)
A^,
oC
and
f
no manual
or auto ranging
js
possible.
The
ranges
are
determined
by
the
OO 0055 only,
UP. DOWN or
AUT
pulses
are
not
relevant.
Manual
ranging
-
When
the DOWN
or
UP switch
is depressed
a
logic
1 signal
(ü)
will oe
connected
to
the relevant inputs
of
the
oo
0059. The
logic
1
({)
pulse
is also
supplied
to the kq
input
of thyristor
V 1b0.
The thyristor
witl
start
conductjng
and
the
-8.5
V
(logic
0) which
is
supplied via
the
function
switch
to
R
723 aod R
].24
will
also
be
connected
the
AUT input
of the
OO OO59
(no
auto rangingJ.
The
thyristor
will stay in
this
state until
it is
switched
via
the
aq input.
The
-
8.5
tevel
is aiso
suoplied
via
the thyristor
to
transistor
V705
causing
the
A
indication
lamp is
lignreo.
-
Chanqing
rhe
above mentioned
state
can
only be
done when
switch
AUT is depressed
or
when
switchjnq
from
a function
with no
ranging
facilities
to a
function
with ranging
facilities.
Auto
ranging
-
When
swirch
AUT
is
depressed
a iogic
I
(g)
wiil be
connecred
to the AUT
input
of
the OO
0059. Also
a
logic
1
{ü)
is connected
to
the aq input
of
the thyristor
and
the input
or rransrstor
V
705.
The
UP/DOWN
inputs
of the
OO
0059 are
connected
ro logic
0
(_g.5
V)
again and
the
lighring
of the
MAN
indication
is stopped.
(or
A indication)
-
When
the instrument
is
switched
on or when
it
is
switched
from
ranqes
(m)
A
I _
,
(m)
A.v,
oC
o,
to
ranges
V-.
V-
or kf/
visa versa,
the instrument
will aiways
start in
MAN ranqe
mode.
DH
With
the
data hold
signat
is
possible
to hold
the data.
This
means
that
the
present
value
of the last
completed
measurinq
will tle held.
Data hold
rs generated
In
two wavs
viz:
-
External
by interconnecting
point
S
of the
probe
input
to circuit zero
(#)
or
O socker
-
lnternal
during range
switching
in
the functions
V-
and
{m}A-.
Resistors
R
| | 6 and
Rl
| 7 are
used
as cutent
limitots,
so that
the
output of the
one shot in
the
OA
0059 is not
short
circuited
in case
af
external
data hold.
DH
loqic
1 means
end
of measuring
cycle
and no
transfer
pulse
of measLrred
data.
The
control logic
is waiting
until
DH
becomes
logic
0 The instrument
is
measuring
but
the
data is
not ciisplayed.
At
the same
Irme arso
signals AZ
andAZ
are
bloo<eo.
The
DH
signal
is
also active
in
the V-
and
(m)A-
functjon
when rs
switched
from
one range
to another-
Via
a
one shot
DH
is active
for
about
4g0
msec.
(Refer
to
OO 0055,
chapter
3.4.3)).
FA, FB, FC, FD
The function
code
is determined
by
the switches
o{ the function
setector.
Dependent
to the function
selected
FA.
FB,
FC,
FD have
a
certarn
code.
(Refer
to the specification
of OO
0055,
chapter
3.4.3.).
In case
of
10 A
signal FD
is switched
by
means
of
the banana
plug
activating
the switch which
is srtuated
inside
the l0
A socker.
3.3,4.4.
Output
Signats
(Fig.
54
and
22)
RNG
A,
RNG
B, RNG
C
Range
in{ormation
from
the
oooo59
is determined
by the
signats
uP/DowN
and {2which
are supplied to the
ranging
counler.
Dependent
to the range
selected
a
specified
range
brock is
avairabre.
Reter
to specification
of
oe
0059.
Chapter
3.4.4.
l-
t
L
t
r
L
r
L
0
t
t
t
t
t
t
t
t
Ij
d
i
d
d
I
t