DI-4108 and DI-4208 Hardware Manual
Controls, Indicators, and Connections
13
Low-pass Filter
Each analog channel employs a low-pass filter with automatic corner frequency selection. The filter is a CIC (cas-
caded integrator comb) type that uses as many as 512 samples per channel to calculate in real time as data is acquired.
Filter response is optimized when sampling frequency is set to ten times the highest frequency of interest.
The DI-4108 and DI-4208 calculate its own Last Point, Maximum, Minimum, and Filter data making it available at
the programming level. Acquisition methods “RMS” and “Frequency” are permanently disabled for the DI-4108 and
DI-4208, as are Input Types “Nonlinear” and “Thermocouple” and selections for “Unipolar” and “Fahrenheit.”
Resolution as a Function of Sample Rate
The resolution of the DI-4108 and DI-4208 is a function of sample rate. The lower the sample rate the higher the res-
olution. ADC resolution (R) is a function of selected sample rate per channel (F), and the number of enabled analog
channels (C):
C
Enabled Channels
1
1
2
2
4
3-4
8
5-8
