Datron 1062 - Page 19

10
1.7
CALIBRATION USING
KEYBOARD'
1.7.1
General
The 'KEYBOARD' method of calibration is useful
when a calibration source although set to a nominal value
has known errors. In this situation the known value of
the
calibration source
can
be entered
into
the
DVM before the
'AUTOCAL' process is executed. The process
is
functional
during
any calibration with
a
source of magnitude between
20% and 200% of the range selected,
but
it should
be noted
that for equal magnitude
source errors, calibrating at the
lower
percentage end of range produces
a
higher
percentage
calibration error. The
'KEYBOARD' method operates for
both the 'Gain'
and
'AcHf'
calibration operations.
An
example using
'KEYBOARD' to calibrate directly
against
a Standard Cell is
shown
in
the
table
below.
1.7.2
'KEYBOARD' with Negative Inputs
If
the
'KEYBOARD'
method is used
on DC Voltage
calibration with Negative polarity
sources, it is important
NOT to enter a negative sign with
the keyed-in source
value. The
instrument itself can determine
the polarity of
the
source
and
update the
appropriate calibration
memory
location.
1.7.3
'KEYBOARD' Calibration
Example
The example shown in the table below
uses
'KEY-
BOARD' to
calibrate
the 1000V AC LF Range Gain at
500V (step 15 of the AC
Voltage Calibration
table for
Option 12).