Philips pm2521 - Page 30

In
the function
selector
positions
A
.t: or
A
~
two
offset measurements are performed.
a) A 200mA I
zero
measurement (offset)
b) A 2 A I
zero
measurement (offset)
The PM2521 measures
the
offset in the
I to V convertor and this is subtracted from
the result of
a normal
measurement
in
these two ranges.
All the above measurements are completely
controlled by the microprocessor
software.
The following sub-
routines are used for internal
test and adjust routines:
—
Comparison
routine
—
Fetch adjustment number routine
—
Fetch calibration
value routine
Also used as subroutines:
—
The set-up routine
—
The measuring routine
—
The calculation routine
—
The
display
output
routine
Comparison routine:
Here the contents of
a
calibration
measurement are
compared with
a
normal measurement. If
the contents
of both are equal then an internal
bit is set.
Fetch adjustment number routine:
The
ijP
scans port P1
1
and reads the
number of the adjust mode.
k
=
adjust mode 1
*
blinks
Z
=
adjust mode
2
S
=
adjust mode
3
Fetch calibration value routine:
Fetches the calibration
value (i.e. the measuring
time)
from the
low calibration value register and the high
calibration value register and
transfers it to the binary
result register.