Extech Instruments 420 Specifikace stáhnout pdf (Strana 70)

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70

V5.1‐March2010

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Hamming

This is a good window for resolving frequencies

that are very close to the same value with

somewhat improved amplitude accuracy over the

rectangle window. It has a slightly better frequency

resolution than the Hanning selection.

Use Hamming for measuring sine, periodic, and

narrow band random noise. This window works on

transients or surges where the signal levels before

and after the event are significantly different.

Hanning

This is a good window for amplitude accuracy but

less so for resolving frequencies.

Use Hanning for measuring sine, periodic, and

narrow band random noise. This window works on

transients or surges where the signal levels before

and after the event are significantly different.

Blackman

This is the best window for measuring the

amplitude of frequencies but least useful for

resolving frequencies.

Use Blackman-Harris for measuring predominantly

single frequency waveforms to examine higher

order harmonics.

Fig 42, 43, 44, 45 show four types of window functions referring to a sine wave of

1KHz.

1 2 ... 65 66 67 68 69 70 71 72 73 74 75 ... 108 109

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Extech Instruments 420 Specifikace Strana 70