output voltage is directly proportional to the altitude (Section 201.3
equation 6).
Therefore, the compmsation added to the radiation signal
will be a logarithmic function of the altitude.
The proper compensation
voltage for an area contaminated with radioisotopes can be determined
by taking two passes over a level section of the area, one at 500
and the second at 1000 feet.
The ratio of the readings obtained at
the two altitudes can be used to determine the voltage applied to the
altitude compensation potentiometers.
description of this procedure).
(See Section 2.4.4 for a full
Once the voltage has been determined
and set, the instrument will properly compensate for any altitude
over an area with a similar type of contamination.
However where
these values have previously been determined, the altitude compensation
voltage may be set prior to operation.
Since the rotation of the indicator shaft of the radar altimeter
(APN-22), which has been used with this instrument is not a linear
function of altitude, the resistance of the automatice compensation
potentiometer (R-Ly) was computed to produce a linear change with
altitude.
It has been reported that the newer models of the altimeter
may have linear output characteristics available thus permitting the
use of standard linear potentiometers.
2.1.5
Power Supply
All power for the "Top Hat" airborne detector is obtainsd
from an internal supply of mercury cell batteries, which have been
selected because of their flat voltage discharge characteristic and
sharp voltage drop off at the end of useful life.
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