General Tools and Instruments DSM8925 - Manual (Page 9)

To measure the loudness of a sound
source, point the microphone at it.
The meter’s default settings are autoranging
on (enabling measurements from 30 to 130
dB), fast time weighting and “A” frequency
weighting. When the meter is powered on,
AUTO will appear on the left side of the
display, with FAST on the top line and A on
the right side. Following are procedures for
changing each of these settings to suit the
application.
AUTORANGING VS.
MANUAL RANGING
The DSM8925 has four measurement ranges:
40 to 70 dB, 60 to 90 dB, 80 to 110 dB, and
100 to 130 dB. When the meter is powered
on, it automatically enters Autoranging mode.
In this mode, it automatically switches to the
range that displays the input with the finest
resolution. For example, the meter could
display a sound level of 65 dB using either the
40 to 70 dB or the 60 to 90 dB range. In
autoranging mode, it would choose the lower
of the two ranges (40 to 70 dB) because on
this scale 65 dB has a better (finer)
measurement resolution.
If you already know the loudness range of the
machine or environment you wish to measure,
and that range is limited, consider exiting
autoranging mode and operating the meter in
only one of those four fixed ranges. The
benefit of operating the meter in this mode—
called Manual Ranging mode—is speed.
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