Campbell Scientific CR9000X Measurement and Control System - Manual (Page 113)

Section 3. CR9000X Measurement Details
The integration and Sinc filter order that a given CR9058E is
using can be seen through RTDaq's terminal mode window
(DataLogger/ Terminal Emulator) or any other terminal
emulator. Click on "Open Terminal", then hit "Enter" several
times until the CR9000> prompt is returned. Type in "4" and
enter. The CR9058Es' slot numbers, integration times, and Sinc
filters will be returned. TIP
FIGURE 3.2.2-1. Depiction of a 5th order Sinc filter
As shown, the number of samples required to feed a fifth order Sinc filter with
an integration of 288 uSec is 11. The number of samples required for filter
orders of 2 and above can be calculated using equation 3.2.2.
Eq. 3.2.2
( )
1 ) 1
96
( + − =
IntegTime
r FilterOrde mples NumberofSa
The CR9058 firmware limits the number of samples to 680 in order to reduce
the amount of time required to compute the weighting coefficients. If the
calculated NumberofSamples is greater than 680, then the Filter order is
incrementally reduced until either the Number of Samples is less than 680, or
the Filter Order is 1. A filter order of 1, simple averaging, does not require
storing multiple values.
Solving equation 3.2.2 for the maximum integration time based on the filter
order results in:
Eq. 3.2.3 96 )
1
( ∗
+
=
r FilterOrde
fSamples MaxNumbero
Integer me MaxIntegTi
Or 96 )
1 680
( ∗
+
=
r FilterOrde
Integer me MaxIntegTi
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