Ohmsassembly - Datron 1061 Calibration And Servicing Handbook

53
Analog Assembly (A-D converter)
23.
Select
100V
range and
apply short
circuit between
Hi and Lo.
Conn-ect
OVI¡'H¡
þ
-fP7,
Lo
to
TP20'
lf
reading
is
+6.42y +0.03V proceed
to
step 25'
24.
Switch
off
instrument
and
make positive
reference
links
B &
C,
if cut
¡.e.
the links
alongside
TP7' Switch
on
instrument and
measure
voltages
on TP7
once
again. Consult
F¡g.
4.1
and
cut links
as
indicated'
Repeat step 23.
33.
Apply +19 volts.
lf
the display
reads
within
the
limits
+18.99g9 to
+19.0001.
proceed
to
step 35.
34.
Calculate
E
=
(lg -
displayed readingl/2.
Re-apply
+10 volts and adjust R23 for a
displayed
reading
of
10
-
E.
Repeat steps 32-34
until
both
readings
are
within the
lim¡ts
¡ndicated.
35.
Turn
rear panel
keyswitch
to
RUN
mode.
The
basic DC
only
instrument set-up procedure
is
complete.
4.3.2
Ohms Assembly
Equipment
Required:
5%
digit DVM,
e.g.
Datron
1065,
or
1061.
10
Megohm 5% resistor
in
parallel
with a
10nF capacitor,
ê.9.
Datron Part No.400392.
Copper
shorting links,
and
a
short
wire
link.
Procedure.
e
25.
Connect
DVM Hi
to
TP8.
lf
reading
is -6.42V
+
0.03V proceed
to
step 27.
26.
Switch
off
instrument
and
make negative reference
links
A to
C,
if
cut i.e. the links
alongside
TP8.
Switch
on
instrument and
measure
voltage
on
TP8
once
again.
Consult Fig
4.1 and cut links
as indic-
ated.
Repeat
Step 25.
27.
Select HOLD.
Connect
DVM
Hi
to
TP9.
Select
correct
resistance value
for
FSV
R11
or
R15
to
give
a reading
of 0V !1 mV.
Solder
in
resistor.
28.
Deselect
HOLD and disconnect DVM.
Select 1000V
range
and apply +19mV. Connect
oscilloscope
Lo
to
TP21
,
Hi
to
TPS.
Adjust
R20
for
noisy waveform
at zero Point.
29.
Remove oscilloscope.
Replace
covers
but do
not
replace
screws.
Select
1V,
DC,
filter out
and
apply
l
MCl
across
input
terminals.
Turn
rear panel
key-
switch to CAL
mode and select
LlN.
30.
Select
.lV
range
and
apply l0lVlf)
across
input
ter-
minals. Select
Ib.
Repeat
until
display
reads
less
than
50 digits.
31
Select 10V
range,
FILTER and apply short
copper
link
across
input
terminals. Select
ZERO.
32.
Apply +10
volts and select GAIN.
Repeat until
display
reads
+10.0000
+
%
digit.
Select 10
kilohm
range,
4-wire.
Connectf- to
Ohms
Guard,
L+
to
Hi, and 10 Megohm resistor between Hi
and
Lo.
Connect
DVM
H¡
to
TP4,
Lo
to TPI
and
adjust
R26
(bias
current) for
a
reading
of
Zero
t
300¡tV.
Disconnect
the
10
Megohm resistor,
and connect
a
copper shorting
link in
its place between
Hi and
Lo.
Transfer DVM Hi
from
TP4
to
TP14, and adjust
R27
(010 offset)
f
or Zero
+
2pY
.
N.B.
Ensure
that the DVM
used
for
measurement
is
correctlY zeroed!
Repeaì steps
1'4 unt¡l the
readings
are wíthin
the
specified limits.
Connect
Lo to
Ohms Guard.
Connect
a
shorting link
between
TPl
and
TP3'
Transfer DVM
Hi from
TP14
to
TP13, and
check
that
the reading
is zero
*
50¡rV.
lf
reading
2
+50¡rV,
reselect
FSV resistor R40
to bring the
reading
within limits'
lf
reading<-50¡¡V, reselect
FSV resistor
R39
to bring the reading
within limits.
N
B
R39 and R40 must
each be
at least 100 kilohms.
Remove
the
link from TPI
and TP3. Disconnect the
DVM
leads,
and
the connections
from
the
front
panel.
The basic Ohms
set'up
procedure is
now complete.
1
2.
3.
4.
5.
6.
7
I
TL'C'
TL'B'
Voltage
on
TP7 or TP8
6.42
6.47
6.525
6.58
Select voltage closest
to
measured
value
and
cut links
FIG
4.1
REFERENCE
SELECTION VOLTAGES