NTi Audio Acoustilyzer AL1 - Manual (Page 27)

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Input Range Selector & Bargraph
In the SPL/RTA Mode the AL1 has three measurement ranges (RNGE).
The span of each range depends on the sensitivity of the microphone
used. For a MiniSPL with a sensitivity of 20mV/Pa the measurement
ranges are:
20 to 100 dB 40 to 120 dB 60 to 140 dB
The selected input range is displayed at the bottom of the bargraph and
may be changed by operating the range indicator arrows. The bargraph
provides an analog display of the actual sound pressure level.
Primary Indicator Range
To achieve best measurement accuracy the appropriate range,
called the “primary indicator range”, must be selected. Correct setting
avoids overflow indications and lowers the influence of noise on the
measurement result.
The two range indicator arrows assist the user to set the optimal range.
As soon as the indicated bargraph value is found lower than the primary
indicator range, the down arrow symbol below RNGE will start to move,
symbolizing that the actual SPL measurements are inaccurate. The
bargraph range needs to be changed manually by selecting the moving
left arrow symbol and pressing the enter key.
Note: Changing the ranging resets all ongoing measurements.
When exceeding the primary indicator
range, three overload arrows replace
the big result reading.
• Select the right arrow below RNGE
and press enter to change to the next
higher bargraph range.