General Tools and Instruments DSM8925 - Manual (Page 14)

However, the digital display is updated only
when the meter detects a louder sound.
To enter MAX HOLD mode, press the MAX
HOLD button at the lower right of the front
panel. To exit this mode, press the MAX HOLD
button again
DISABLING AUTO POWER OFF
By default, the meter powers off automatically
after 20 minutes to avoid discharging the
batteries. However, you can disable this
feature if you would like to track sound levels
over a longer period of time. For this purpose,
you will also need to feed the meter’s analog
output signal (available via a jack on the right
side of the unit) into a chart recorder or data
logger.
To disable Auto Power Off, first power off the
meter by pressing the
button. Then power
on the meter in a special way by pressing the
button and pressing and holding the MAX
HOLD button at the same time. This will cause
the letter “n” to appear briefly on the digital
display. Once “n” has appeared, you can
release the MAX HOLD button.
Once Auto Power Off has been disabled, the
meter will no longer shut down automatically
after 20 minutes. It will remain on until the
button is pressed again to power off the
instrument. Once the meter is powered off,
Auto Power Off will automatically be re-
enabled when the meter is powered on again.
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