Larson Davis 831, User Manual

Page: 40 / 548

Model 831 Manual Summary of Displays and Icons 3-9
When using a microphone having a sensitivity of 50 mV/Pa,
the input overload will occur approximately as shown in
Table 3-4.
Under Range Icon
When the signal from the preamplifier drops to the point
where the noise level of the instrument and the preamplifier
influence the measurement, an under range condition exists.
When this happens the Under Range Icon will appear.
As long as the under range condition exists, the icon will
flash. When the measured level no longer produces an under
range condition, the icon will be removed from the display.
At any time when a measured parameter is in an under range
condition, it’s numeric display will appear in grey rather
than the usual black, as shown FIGURE 3-7.
FIGURE 3-7 Normal vs Under Range Data Display
OBA Overload Icon
If the input to the Octave Band Analyzer (optional firmware
831-OB3 required) becomes overloaded, the icon shown
will appear to indicate the overload.
This icon operates similar to the Input Overload Icon shown
in the above section "Input Overload Icon".
When the OBA Range property is set to Low, the OBA
Overload Icon will activate at a level 33 dB lower than it
would had the OBA Range been set to Normal.
Input Gain, dB Overload Level, dB Peak
0 143
20 123
Table 3-4 Input Overload Levels
Normal Range
Under Range