Norsonic nor140, Instructional Manual

Page: 50 / 220

32
Chapter 5
Frequency analysis
Making a frequency analysis
To start a frequency analysis measurement:
• Set the measurement duration.
• Press the
START
key. The R in the display indicates
that a measurement is running. The measurement is
running and data acquired irrespectively of whether
the frequency spectrum is shown or not.
To temporarily halt an ongoing measurement:
• Press the
PAUSE/CONT
key.
To resume a paused measurement:
• Press the
PAUSE/CONT
key again. Upon resuming
the instrument will go on measuring until the total
measurement time elapsed equals the preset dura-
tion. Observe that data acquired immediately pre-
ceding the pause may be erased because of the
back-erase function (see below).
To terminate an ongoing measurement:
• Press the
STOP
key.
To resume a terminated measurement:
• To resume a terminated measurement press the
PAUSE/CONT
key. Upon resuming the instrument
will go on measuring until the total measurement time
elapsed equals the preset duration. When a terminated
measurement is resumed, the back-erase feature (see
below) will
not
be activated.
To switch between absolute and relative time:
• To switch between time elapsed since start of
measurement (relative time) and date + time of day
(absolute time), use the
ABS
t
key.
Switching to displaying the spectrum
Having activated the frequency mode and left the
menu, just press the
f
↔
t
key to display the level
vs. frequency and press again to return to the other
display. Since no measurement has been made the
only function producing frequency band bar graphs
will be the SPL with the selected time constant. If you
press the
FUNC
key this will produce empty displays
only. If you did, just keep pressing the
FUNC
key until
the SPL reappears.
Switching between sound level meter display
and spectrum display
Sound level meter
display
Spectrum display
2
As long as the frequency mode has been
activated, frequency analysis will be made
during every measurement. This means
that the instrument will combine a “traditional” sound
level meter measurement and a real time frequency
analysis in octaves or third-octaves. Whether the
instrument is set to show the spectrum or the classic
sound level meter display will not affect the measure-
ment in any way. Likewise, going between the two
displays modes during a measurement has no effect
on the measurement either.