Guralp-systems Scream Manuel d'utilisateur télécharger pdf (Page 84)

Scream! 4.5

Since it is not generally advisable to trigger from broadband data, the

digitiser provides a set of standard bandpass filters to apply to the data

streams before they are tested for the trigger condition. This filtering

serves to maximise sensitivity within the frequency band of interest,

and filter out noise outside this band. You can select which bandpass

filter to use from the Bandpass filter drop-down menu. The corner

frequencies of the pass band of the filter are determined by the Nyquist

frequency, which is given by the sampling rate of the triggering data.

The three filter options have pass bands between 10% and 90%,

between 20% and 90% and between 50% and 90% of the data’s

Nyquist frequency, respectively.

The possible filter configurations are:

Tap #.

Rate

(samples/

Bandwidth 1

(Hz)

Bandwidth 2

(Hz)

Bandwidth 5

(Hz)

0 200 10 – 90 20 – 90 50 – 90

100 5 – 45 10 – 45 25 – 45

50 2.5 – 22.5 5 – 22.5 12.5 – 22.5

40 2 – 18 4 – 18 10 – 18

25 1.25 – 11.25 2.5 – 11.25 6.25 – 11.25

20 1 – 9 2 – 9 5 – 9

50 2.5 – 22.5 5 – 22.5 12.5 – 22.5

25 1.25 – 11.25 2.5 – 11.25 6.25 – 11.25

20 1 – 9 2 – 9 5 – 9

10 0.5 – 4.5 1 – 4.5 2.5 – 4.5

8 0.4 – 3.6 0.8 – 3.6 2 – 3.6

5 0.25 – 2.25 0.5 – 2.25 1.25 – 2.25

4 0.2 – 1.8 0.4 – 1.8 1 – 1.8

2 0.1 – 0.9 0.2 – 0.9 0.5 – 0.9

25 1.25 – 11.25 12.5 – 11.25 6.25 – 11.25

10 0.5 – 4.5 1 – 4.5 2.5 – 4.5

5 0.25 – 2.25 0.5 – 2.25 1.25 – 2.25

4 0.2 – 1.8 0.4 – 1.8 1 – 1.8

2 0.1 – 0.9 0.2 – 0.9 0.5 – 0.9

1 0.05 – 0.45 0.1 – 0.45 0.25 – 0.45

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Guralp-systems Scream Manuel d'utilisateur Page 84