Laboratory tests of our first AGI inclinometer (
354) during the summer of
1994 showed noise levels meeting our demands, viz <0.1" r.m.s..
Tests of its sensitivity in single-ended mode and high-gain gave
99.3mV/" + 1% cf manufacturer's figure of 97.1.
Differential mode is twice as sensitive and since it includes built-in
protection against noise spikes it is likely to be our preferred method of
operation. The useable range is +80" in single-ended mode,
half that in differential mode. This is sufficient to meet expected excursions
due to track irregularities, but leaves little room for significant changes in
track profile in the future. The low gain settings are all 10 times coarser, and
all the data taken on the antenna during September 1994 used the low gain
settings.
The output voltages from the meters need to be zeroed in order to minimize
temperature effects which are proportional to the output voltage : approximately
5%/degree , although any zero-point change ought to be correctable using the
temperature reading for each device.
However, attempts to measure zero-point drifts of the inclinometers resulting
from the diurnal temperature cycle were confused by possible tilting of the
local topography with the diurnal cycle.