B&K 2250 Light Manuel d'utilisateur télécharger pdf (Page 16)

CHAPTER 2

Measured Quantities and Parameters

• ∆t is the display update interval, equal to 1 second

The sound pressure level is, in other words, updated every 1 second and is expressed in decibels (dB).

The symbols used on the screen of Type 2250 for sound pressure levels are (for A, C and Z frequency-

weighting and F, S and I time-weighting):

(SPL), L

(SPL)

2.5.3 Timed Broadband Measurements

These measurements are only executed when Start is activated and are paused when Pause is activated

or when Preset Time has expired, whichever occurs first. The time interval between start and pause is

the Elapsed Time. During the measurement time interval, intermediate results are displayed as if the

measurements were paused at the time of display. When the measurements are paused, the set of

results, including Latched Overload and Overload %, are stored under Current Measurement and this

is held until either Reset is activated or a new set of measurements are started. The Current Measure-

ment (if any) is displayed and can be saved, together with setup and calibration information, to a

project.

Latched Overload

For the timed measurements, a Latched Overload indication is displayed and included in the set of

results if the overload condition exists at any time during the measurement time interval. The latched

Overload is indicated by a red triangle on the screen. The Latched Overload is common to all the

results of the timed measurements.

Overload Percentage

The Overload Percentage, Overload %, is defined as the percentage of time within a time interval

starting at t = T and ending at t =T+

∆t where the overload condition exists, where:

• T is the start time of the measurement, indicated as Start Time

•

∆t is the measuring period, indicated as Elapsed Time

Under-Range

No under-range indication is given because the instrument only has one range, which extends upwards

from the inherent noise level.

Maximum Time-weighted Sound Level

The maximum time-weighted sound level, L

xymax

(T), is defined as the greatest time-weighted sound

level, L

(t), within a time interval starting at t = T and ending at t = T + ∆t where:

• x is A for A-weighted, C for C-weighted or Z for Z-weighted

• y is F for Fast-weighted, S for Slow-weighted or I for Impulse-weighted

• T is the start time of the measurement, indicated as Start Time

•

∆t is the measuring period, indicated as Elapsed Time

The maximum time-weighted sound level is expressed in decibels (dB).

The symbols used on the screen of Type 2250 for maximum time-weighted sound levels are (for A, C

and Z frequency-weighting and F, S and I time-weighting):

AFmax

, L

ASmax

, L

AImax

, L

CFmax

, L

CSmax

, L

CImax

, L

ZFmax

, L

ZSmax

, L

ZImax

Minimum Time-weighted Sound Level

The minimum time-weighted sound level, L

xymin

(T), is defined as the smallest time-weighted sound

level, L

(t), within a time interval starting at t = T and ending at t = T + ∆t where:

• x is A for A-weighted, C for C-weighted or Z for Z-weighted

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B&K 2250 Light Manuel d'utilisateur Page 16

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