National Instruments NI USB-9234 Understanding NI USB-9234 Data Rates

The filter significantly attenuates all signals above the stopband frequency.

The primary goal of the filter is to prevent aliasing. Therefore, the stopband

frequency scales precisely with the data rate. The stopband rejection is the

minimum amount of attenuation applied by the filter to all signals with

frequencies within the stopband.

Any signal that appears in the alias-free bandwidth of the NI USB-9234 is

not an aliased artifact of signals at a higher frequency. The alias-free

bandwidth is defined by the ability of the filter to reject frequencies above

the stopband frequency, and it is equal to the data rate minus the stopband

frequency.

Understanding NI USB-9234 Data Rates

The frequency of a master timebase (fM) controls the data rate (fs) of the

NIU SB-9234. The NI USB-9234 includes an internal master timebase

with a frequency of 13.1072 MHz, but the module also can accept an

external master timebase or export its own master timebase. Refer to the

software help for information about configuring the master timebase source

for the NI USB-9234.

The following equation provides the available data rates of the

NIU SB-9234:

fs =

where n is any integer from 1 to 31.

The data rate must remain within the data range. Refer to the Specifications

section for more information about the data rate range. When using the

internal master timebase of 13.1072 MHz, the result is data rates of

51.2 kS/s, 25.6 kS/s, 17.067 kS/s, and so on down to 1.652 kS/s, depending

on the value of n. When using an external timebase with a frequency other

than 13.1072 MHz, the NI USB-9234 has a different set of data rates.

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