Datron 1061 Calibration And Servicing Handbook page 9

2
'AcHf'
'
This
flattens the
response
of
the
A'C' ampli-
fier
used
for
AC voltage measurement'
lt
should
only
be
used when
a
full
calibration
i.e' '7ero',
'Gain' and
'AcHf'
is
carried out.
As
with
'lb'the calibration action is
iterative
and
requires
several
operations
of
the key
to
complete'
'Lin'
'
This
is an important
calibration operation
as
it
optimises
the
basic
linearity of
the internal measurement
circuitry
used
for all
ranges
and
functions.
lt
must be used
before any
DC voltage
or Ohms calibration
is
carried
out'
1.1.3.4'AUTOCAL' usins'KEYBOARD'
This
is
an
extension
of
the
'AUTOCAL'
process
which is useful when using a calibration source
set
to
a
nominal value
but with
known errors. This
means
for
example
that
calibration directly
to
a
standard
cell
is
possible.
A full
explanation
of
the
procedure
is
covered
in section
1.7.
1.1.3.5 'AUTOCAL'over the
Bus
Each
of the five calibration
operations can
be
control-
led
using Option
50, the IEEE
bus.
This
means
that
the
instrument can
be entirely calibrated remotely
or
under
program control. As
mentioned
in the 'Procedure Outline'
for a
manual
calibration, the rear panel
address
switch
should be set
to 31,
i.e.
all
1's. When a bus
calibration
is
required
the
address
switch must be set
to
the
address
number
assigned
to the
DVM
in
the
system.
More
details
of
calibration
with the
bus
are included
in
section
1.8.
1.2
DC VOLTAGE CALIBRATION
1.2.1
General
The procedure
in
the table
opposite is
all that
is
necessary
to
completely 'AUTOCAL'
the DC
voltage
function.
Steps
1 and 2 affect the
accuracy on
all
ranges
and
should
therefore
be carried out
even
if just
one
range
is
being calibrated.
On
each range
a 'Zero'
and 'Gain' calibration
is
required
for
each
polarity of input.
The
two 'Zero'calibrat-
ions are included
to
overcome
a
possible
zero difference
w¡th the polarity
setting
of
the
DC calibration
source.
lf
the 'DVM
Reading
After
Calibration'
is not
in
accordancr
with the table,
repeat operations
of
the
same
'CALIBRATE'
key
are
permissible. Where
no
tolerance
is
shown
in this
column,
only
the exact
reading
quoted
with
an occasional least
significant
digit
showing is
to
be
expected.
1.1.3.6 'Er¡o¡ 4'
lf
during calibration 'Error 4'
is displayed,
this indi-
cates
that the
Calibration Source
deviates
too far from the
calibration
span
of
the instrument.
Under these circum-
stances,
the
calibration memory
is not
updated and the
instrument
goes
into 'Hold' with
the
calibration button
calibration
key
LED remains on.
ln the
case
of 'Zero', 'Gain' or 'AcHf'the
Calibration
Source
should be checked and the
same
'CALIBRATE'
key
repressed.
The 'Hold' mode may be
released any
time and the
instrument
will
free run
again.
lf
'Error 4'
follows
'Ib'
or
'Lin'or
persistently
appears
following 'Zero',
'Gain'
or
'AcHf' then an
instrument failure may
have
occurred. Therefore
either consult our
Customer
Service
Sectíon
or the Servicing Section
of this
Handbook.
I
1.2.2 Equipment Required
-
lMO'Lin'Source.
This
is
a
1MO 5% resistor
in
parallel
with a
1nF
capacitor, shíelded
to
reduce
noise
i
nte rfe
rence.
-
10MO'Ib'Source' This is a
10MO
5% resistor in
parallel
with
a
1nF capacitor,
shielded
to
reduce
noise
i
nte rfe
re
nce.
Datron products, number 400391 and 400392,
are
available
as
'Lin'
and
'Ib'
sources
and are
recommended.
-
A DC Calibration Source.
e'g': Datron
4000/40004
Autocal
Standard.
1.2.3 Checkíng
Accuracy
after'AUTOCAL'
To
check
the
accuracy
after
'AUTOCAL'the
'Specification
Verification' section
of the
User's
Handbook
will
be
useful;
it
provides tables
for quick
reference
of
accuracy
on
all
ranges
and
functions in displayed digits'
I
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