Norsonic nor140, Instructional Manual, Page: 20 / 220

2 2
Introduction
instrument without affecting the value of the same
parameters in another mode of operation. If you close
a mode and return to it later, the value last used for
these parameters will be automatically loaded.
The main features – an overview
Level vs. time.
The electronic level recorder concept
is available in two versions – basic and enhanced.
While the basic version logs the equivalent level, the
maximum level and the peak level, the enhanced
version is capable of logging any combination of
functions available with the Nor140. In addition it
allows source coding.
Another difference important for some applications
is that while the basic version has a time resolution
ranging from 1 second and upwards, the enhanced
version has a time resolution from 50 ms and upwards
in 25 ms steps. Above 1 second the time resolution is
available in 1 second steps for both versions.
Frequency analysis.
When fi tted with the frequency
analysis extensions the Nor140 can make real time
frequency analysis in octaves or third-octaves.
The functions measured are the equivalent level,
the maximum level and the minimum level.
The frequency range is 0,4 Hz to 20 kHz and thus
covers both the audio and the vibration range.
Statistics.
The optional extension 4 adds statistical
distribution to the Nor140 functionality. There are eight
percentiles shown, out of which one is freely selecta-
ble. The class width is 0.2 dB over the entire 130 dB
range.
The statistical distribution calculation applies to the
spectral weighting networks (A and Z or C) as well as
all the individual fi lter bands (if applicable).
The back-erase feature, which deletes up to 20 (se-
lectable 0 - 20) of the most recent seconds of acquired
global data prior to a pause upon resuming, updates
the statistics buffers as well to maintain consistency.
For the statistical sampling the instrument makes
use of the F time constant, irrespective of what time
constant(s) the frequency analysis as such employs.
The fi xed percentile levels offered by option 4 are
1.0%, 5.0%, 10.0%, 50%, 90%, 95% and 99%.
In addition, one of these percentiles is subject to
user-defi nition and can be set to anything from 0.1%
to 99.9%, both extremes included. Note that you don’t
have to defi ne the percentile prior to the measurement.
You may redefi ne the percentile as many times as you
like – even after the measurement! For every frequency
band measured!
However, once you start another measurement or
switch off the instrument, only the selected percentiles
will be available to keep the amount of stored data
lower.