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Norsonic Nor150
Instruction Manual
Measurement time
The ISO 9614:1 defines a minimum measurement time
in each position depending on the lowest frequency
of interest. In the default configuration, 50 Hz is the
lowest frequency band. The minimum time in this case
is 35 seconds, as seen in Figure 21.60. We recommend
setting the
Global Time
to your desired value. The
Nor150 will automatically stop a measurement when
the
Global Time
is reached.
While measuring according to ISO 9614-1, it is also
possible to measure and watch the measurement in
short-term profiles. Set the
Profile Time
to any desired
interval to exploit this capability. We recommend 100 ms
for general measurements.
Filtering
Filter
controls the main filtering functionality. We
recommend measuring with the filter setting left
default, providing data from 20 Hz to 20 kHz.
Weighted Sum Freq Range
controls the frequency range
evaluated for the field indicators and for calculation of
A,C and Z. The standard specifies that the frequency
range must be set to 50 Hz to 6.3 kHz. A warning will be
given if the weighted sum frequency range is changed.
In certain cases, it may make sense to use a wider
or narrower range. In these cases, the user will need
comment and consider the uncertainty and complience
to the standard.
Excluded bands
is a list of excluded bands. In certain
cases, it makes sense to exclude certain bands.
Exclusion may be done from this menu, or directly in
the graphs during measurement or evaluation.
Figure 21.60 - Setup
menu when measuring
according to ISO 9614-1.
Measurement precision
Select the desired measurement precision by altering
the
Accuracy
setting:
• Survey / Grade 3
4 dB standard deviation in A-band
• Engineering / Grade 2
1,5 dB to 3 dB standard deviation in third octave
bands.
• Precision / Grade 1
1 to 2 dB standard deviation in third octave bands
Please refer to Table 2 in ISO 91614-1:1993 for details.
The higher the accuracy, the more stringent
requirements for the field indicators, and thereby also
the number of measurement positions.
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