Datron 1061 - Basic DC Lnstrument

52
2
3.
4.3.1 Basic
DC
lnstrument
Equipment
Requ irements:
4%
digit
Digital
Voltmeter e.g.
Datron
1041
Variable
5V, 1 amp
DC supply
5mV/division
Oscilloscope
e.g'
Telequipment
D83
1MO5% resistor
in
paiallel
with
10nF
capacitor
10MS)5%
resistor
in
parallel with
10nF
capacitor
DC
Voltage
Calibrator,
e.g.
Datron
4000/40004
Autocal
Standard.
Procedure
Power Supplies
Turn
instrument
on and
allow
5
minutes
warm-up
period.
4
Connect
DVM
Hi to
TPB
and
Lo
to
TP28
on
the
Digital
assembly. Adjust
R2
on
the
Rear
(Power
Supplyl
pcb
assembly to
give
+5.100V
+25mV'
Connect DVM Hi
to TP1
and
Lo to
TP20
on
the
Ana-
log assembly. Adjust
R7 on
the
Rear
(Power
Supply)
pcb
assembly to
give
+15.000V
+
15mV.
Connect
DVM
Hi to
TP2
and Lo
to
TP20
on
the Ana')
log assembly.
Adjust
R12
on the
Rear
(Power
Sup-
ply) pcb
assembly
to
give
-15.000V
+
1smv.
13.
lnsert
calibration
key into
keyswitch
on
the back
panel
and
turn,
placing
the
instrument
into
CAL
mode,
NOTE:
The
display
CAL tegend
will
be
lit.
14.
Short
together
pins
'D'
and
'E' on
Digital
assembly'
NOTE:
All the
calibration
store
correction
factors
are
now
reset
to
zero,
15.
Turn
the calibration
key back to RUN
mode
Analog
Assembly
(DC
lsolator
Section)
16. Centralize
R150 and
R160.
17.
Select
0.1V range DC with
FILTER out.
Apply
a
10MO
resistor
between
instrument
H¡ and
Lo'
Connect
DVM Hi to TL8, Lo to
TP20.
Adjust
FSV R152 with a metal
film resistor
(5Oppm/oC)
for
a reading of
<
10mV,
using
R159
f
or
'f
ine' adjustments.
Do not solder
in
R152.
18.
Apply
a short
circuit
across the
input terminals
and
adjust
R 1 50
for
a
reading of<
50¡rV
at TPI
3.
19. Connect
DVM
Hi
to
TP33
and
adjust R160
for a
reading
of
<20¡¡V.
20.
Repeat
steps
17
to 19
until
readings
are within
specified
limits.
NOTE:
The
following
step
is only
required
after
the
replacement
of
012 or
any
component
associated
with the
temperature
compensation
circuitry.
21
.
(il
Re-apply
1OMQ
resistor
across
the
input
terminals.
Note
the
reading
on
the
front
panel
display
(=A).
(i¡)
Note
the
ambient
temperature
(=XoC).
(ii¡)
Place
the
instrument
in a
temperature
con-
trglled
oven
at
approx
50oC
without
top cover
and
with
Power'on'.
(iv)
Leave
the
¡nstrument
for
at
least t
hour
then
note
the
reading
on
the
display
(=B)
and the
temperature
of
the
oven
(=YoC)'
(v)
Compute
(B-A)/(Y-X)
=
Drift/oC'
(vi)
Remove
instrument
from
oven
and
allow
to
stabilize,
with
power
'on' to
ambient
for
one
hour.
(vii)
lf
the
drift
was
(10
digits/oC
p-roceed
to
(x)'
(viii)
For
drifts
in excess
of
10 digits/oC
R151 must
be
adjusted.
lf
the
drift
was
positive
turn
R151
clockwise.
if negative
turn
R151 anti-
clockwise'
(ix)
Repeat
from
(i).
(x)
Lock
R151
with
a clean
soldering
iron'
(xi)
RePeat
steps
17 to 20.
22.
Solder
in
R152,
with
instrument
turned
off
'
5.
þ
Digital
Assembly
Switch
the
instrument
off
and disconnect
the
power
lead.
lsolate
the
Digital
Board
by removing
the connectors
along
the
centre
Panel
(J1-J5).
Connect
variable
5V
supply
and
DVM Hi's
to TP8,
Lo's
to
TP2g.
Reduce
supply to
4'750V
+10mV.
Set
R83
fully
clockwise.
Connect oscilloscope
Lo
to
TP28
and
monitor
M53
pin
40'
Turn
R83 anti'clock'
wise
until
TP30
undergoes
a high to low
transition
(or
begins
to
Pulse
low).
Remove
varíable
supply
and
reconnect
items
discon'
nected
in
steps
5
and
6.
Disconnect
the
oscilloscope.
Switch
on
the
¡nstrument'
10.
Connect
DVM
Hi
to battery'positive
terminal,
Low
to
fP28.
Check
battery
voltage is
>2.5
volts.
11.
Disconnect
DVM
and
connect
oscilloscope
Hi to
Tp25,
Lo
to
TP28.
Adjust
scope
trigger
unt¡l
the
trace
is
triggered
by
the
first
pulse
of
each
reading
burst.
Adjust
R11
so
that
the
pulses
occur
every
Sms
.t 0.Sms.
12.
Place
instrument
into
HOLD. Connect
oscilloscope
Hi
to
TP7.
Adjust
L2
to
give
a stable
+1.05*.0.03V.
NOTE:
This
signal
contains about
200mV
peak
to
peak
high
frequency
noise'
7
8.
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