Campbell-scientific CR9000X Measurement and Control System Manual do Utilizador descarregar pdf (Página 114)

100

101

Section 3. CR9000X Measurement Details

This results in the following maximum integration times for the given Filter

orders (Filter order 1 has no limit as it does not require storing multiple

values):

Filter Order 2: 32,640 uSec Filter Order 4: 16,320 uSec

Filter Order 3: 21,792 uSec Filter Order 5: 13,056 uSec

The equations used to plot the frequency responses for Charts 3.2.2-1 & 3.2.2-2:

Eq. 3.2.4 Sinc Filter Order N:

()

Freq

FreqSin

sponselative

⎟

⎠

⎞

⎜

⎝

⎛

ReRe

CHART 3.2.2-1

FREQUENCY RESPONSE OF SYNC FILTER ORDERS 1 - 5

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0123456

FREQUENCY

NO RM ALIZE D TO (1/IN TE G R ATIO N TIM E )

REL

RESPONSE

Sync Order 1

Sync Order 5

Chart 3.2.2-1 shows the frequency responses times for the Sinc filters available

for the CR9058E. As can be seen, the 1

order Sinc filter does not filter out

the higher frequency components of the input signal. This could result in

higher frequency signals being aliased back to lower frequencies. While the

5th order Sinc filter does a fairly good job filtering out higher order

frequencies, the trade off is that it also attenuates the signal at lower

frequencies as can be seen in Chart 3.2.2-2.

These plots assume equal integration times for all filter orders,

so the 5

order Sinc filter would require 5 times the measurement

time as the 1

order Sinc filter.

NOTE

3-26

1 2 ... 109 110 111 112 113 114 115 116 117 118 119 ... 441 442

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