Philips PM2521 Service Manual page 28

28
1.4. 1.2.
Internal Test
and
Adjust Routine
After
initialisation,
th,e
PM2521
performs two
series
of
measurements
as
shown
in
the following flow-chart.
ST 3372
Fig. 21.
Flow-chart
internal test
and
adjust routine
a)
An
AUTO
CAL
0,1V measurement
b)
An
AUTO
CAL
IV
measurement
When
making
the
AUTO
CAL
0,1V measurement
the
fJiP
programs
the
000063
so that
a
current of lOOjuA
flows through R606, which
causes
a voltage
drop of
lOOmV
across
it
(100/tA x 1kl2
).
This voltage
is
supplied
to the
ADC
and
is
counted by
the
/tP,
stored
in a
RAM
location
and
used
as
reference for
a
normal measure-
ment.