B&K 2250 Light Uživatelský manuál stáhnout pdf (Strana 156)

Hand-held Analyzer 2250 Light – User Manual148

Automatic Gain

Control

†

Off

To ease identification of sound sources by listening, the gain

can be automatically adjusted to keep the average level within

a 40 dB range. When playing back the recorded signal, you

will then hear clearly the whole signal content, whether the

level has been 20 dB or 140 dB.

Set Automatic Gain Control to On to convert the recorded

signal. The recorded signal is stored as a 16 bit wav-file.

Set Automatic Gain Control to Off for recording the signal with

a fixed gain – then set Resolution = 24 bit (recommended) to

cover the full 120 dB dynamic range (from max. input level

and down) or select Resolution = 16 bit and specify the Peak

Recording Level to fit the signal.

Note: If the sound contains very high levels at low frequency,

then a fixed gain is recommended

Resolution 24 bit/16 bit Set Resolution to 24 bit to cover the full dynamic range. Set

Resolution to 16 bit to cover up to 96 dB from Peak Recording

Level and down.

Note: You will only be warned about overload in the recorded

signal if Automatic Gain Control is On or if Resolution is 24 bit

or if Peak Recording Level is set to its maximum value.

Peak Recording

Level

145 dB

135 dB

125 dB

115 dB

105 dB

95 dB

85 dB

75 dB

For Automatic Gain Control = Off and Resolution = 16 bit the

recorded wave file has a dynamic range of up to 96 dB. When

playing back on the analyzer, the dynamic range of the output

is approx. 75 dB. When playing back on a PC it might be even

lower. Set Peak Recording Level to fit the signal.

The values for Peak Recording Level take the sensitivity of the

attached transducer into account. The values shown in the list

here are nominal values for a Type 4189 or 4190 microphone.

Hint: Monitor the L

peak

value during a trial measurement

before selecting the Peak Recording Level

Pre-recording

Time

†

0 to 470 s Recording is started the Pre-recording Time before the trigger

conditions are fulfilled (for example, 5 s means the recording

will be started 5 s before you hit the Manual Event

pushbutton). This is possible because the recording is done

continuously in an internal buffer, ready to be saved as a wave

file. The Pre-recording Time is limited by this buffer size and

the Recording Quality and Resolution:

Quality

Pre-recording Pre-recording

Time limit 16-bit Time Limit 24-bit

HW 1–3 HW 4 HW 1–3 HW 4

Low 110s 470s 70s 310s

Fair 50 s 230 s 30 s 150 s

Medium 30 s 150 s 16 s 96 s

High 10 s 70 s 3 s 43 s

Table A.10 (Cont.) Signal Recording parameters

Parameter Values Comment

1 2 ... 151 152 153 154 155 156 157 158 159 160 161 ... 211 212

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