B&K 281 - Calibration Procedure; Calibration Trigger Conditions; Reference Source Accuracy; Initial Calibration Setup

MODEL 281 CALIBRATION PROCEDURE
The instrument should not requite calibration unless repairs have been
made that change the factory calibration. Prior to calibration the instrument
should
be
checked
for
proper
operation
of
all
functions
and
for
damage
from
physical abuse or unprotected. overloads.
The
following
procedure
should
be
performed
with
reference
sources
of
5%
accuracy
or
better.
Use
E
x
of
less
accuracy
reduces
the
accuracy
of
the
instrument.
PER?
e
vss
The
calibration
is
performed
with
the
top
and
right
side
covers
removed.
То
remove
the
top
cover
from
the
unit,
the
two
screws
holding
the.cover
must
be
removed,
then
lift
the
back
of
the
cover
up
and
slightly
forward
to
clear
the
tabs
on
the
front
panel.
To
remove
the
right
end
panel
[rom
the
unit,
the.top
cover
must
be
removed
first,
then
the
handle
must
be
removed.
To
remove
the
handle,
use
a
small
screwdriver
or
solder
aid
to
remove
the
right
side
retaining
ring.
When
this
is
done
the
spring
washer
and
handle
stud
can
be
removed.
Repeat
this
pro-
cedure
for
the
left
side,
and
remove
the
handle.:
Then
remove
the
three.
screws
which
hold
the
end
panel.
The
end
panel
can
then
be
removed.
from
the
unit.
"
»
To
replace
the
handle
put
the
spring
washer
on
the
handle
stud
with
the
bow
facing
the
inside
of
the
unit
(see
Figure
4).
Using
long
nose
pliers,
grasp
the
center
of
the
retaining
ring
and
press
it
into
the
slot
in
the
handle
stud,
holding
the
stud
with
your
thumb.
à;
Function
RANGE
SIGNAL
AT
INPUT
PROCEDURE
1.
Turn
R36
POLARITY
SENS-
F
ING
OFFSET
pot
full
clockwise.
2.
+DCV,
E
Remove
ІСІ
from
socket.
Con-
nect
a
47
ohm
resistor
(may
be
10%)
from
the
junction
of
R47
and
R48
to
the
ground
at
R49.
Adjust
R40
DC
BAL
for
01
read-
out.
3.
+DCV
100mV
Short
Insert
ICI.
Adjust
R24
Zero
for
01
readout.
Remove
47
ohm
resistor.
4.
“ОСУ
100тУ
+100mV
DG
Adjust
R48
DC
CAL
for
100
readout.
5.
—DCV
100V
+5VDC
+10%
Slowly
advance
R86
POLARITY
SENSING
OFFSET
counter-
clockwise
until
readout
blanks
and
1
comes
on.
14