B&K 2250 Light Manual do Utilizador descarregar pdf (Página 50)

CHAPTER 4

Specifications

4.11 Spectrum Analysis

Note: Spectrum analysis requires Frequency Analysis Software BZ 7223.

Analytical filter design: Optimised Z-transformation of analogue Butterworth filters

Base: 2

Sampling rate: Octave-based down-sampling from 48 kHz

Reference attenuation: 0dB

4.11.1 1/1- Octave band Centre Frequencies

Nominal: 8Hz

, 16 Hz, 31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 16 kHz

Exact (5 digits): 7.8125 Hz, 15.625 Hz, 31.25 Hz, 62.5 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz,

4kHz, 8kHz, 16kHz

Real-time frequency range: 8 Hz to 16 kHz centre frequencies.

Fig.4.27

The shapes of the

1/1- Octave band

filters (from 0 to

–80 dB). The

innermost and

outermost curves

show IEC 61260

tolerances

Fig.4.28

The shapes of the

1/1- Octave band

filters (from 0 to

–3.5 dB). The

innermost and

outermost curves

show IEC 61260

tolerances

1 Only accessible when Extended Low Frequency set to On in the Setup menu.

2 These filters do not fulfil the requirements of paragraph 7.2.3 in the ANSI S1.11-1986 standard. The paragraph states, at which

frequency the anti-alias filter cut-off should be set. For the realisation of the filters in Type 2250, this has no influence on the

quality of the measurements.

Response

(dB)

– 20

– 40

– 60

– 80

980474e

0.01 0.1 1

Multiple of Center Frequency

10 100

Response

(dB)

0.5

– 0.5

– 1.5

– 2.5

– 3.5

980472e

0.5 1

Multiple of Center Frequency

2.0

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