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User's Guide _______________________________________________________________________
80____________________________________________________________________ M210543EN-B
where
I
=
Current range specified
range
(e.g. I
range
−
ln(
VIS
)
ln(
=
i
X
−
coeff
ln(
VIS
)
ln(
max
where
VIS
=
Initial visibility value in meters.
i
VIS
=
Lowest visibility value specified in configuration
min
(e.g. 10 m or 100 m).
VIS
=
Corresponding maximum visibility value (e.g. 2000 m or
max
20000 m).
The corresponding DAC output LSB value is calculated from I
using DAC scale parameters.
Mode 3
Mode 3 is the Videograph mode that is non-linear. The visibility range
from 100 m to 10000 m corresponds to the current range of 1 ... 0 mA.
Mode 4
Mode 4 is the Videograph mode that is non-linear. The visibility range
from 180 m to 20000 m corresponds to the current range of
1 ... 0.1 mA.
Analog Output Calibration
The analog output is initially calibrated at the factory. The analog
output has two ranges, 0 ... 1 mA and 0 ... 20 mA. The range is
selected according to the jumper.
In the calibration command, the internal scaling factors for
milliamperes to hardware control bits are calculated.
PWD22 set two-bit patterns to the DAC circuit and asks for the
corresponding measured currents. If the higher current is less than
= 20 mA - 4 mA =16 mA)
VIS
i
ln
VIS
VIS
)
=
min
min
VIS
)
VIS
min
max
ln
VIS
min
,
by
out
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Troubleshooting
