National Instruments 9225E Operating Instructions And Specifications page 8

The NI 9225E analog input channels are floating with respect to
earth ground and each other. The incoming analog signal on each
channel is conditioned, buffered, and then sampled by a 24-bit
Delta-Sigma ADC.
Each channel provides an independent signal path and ADC,
enabling you to sample all three channels simultaneously. Refer to
Figure 5 for an illustration of the circuitry for one channel of
the NI 9225E.
AI+
Overvoltage
AI–
Figure 5. Input Circuitry for One Channel of the NI 9225E
© National Instruments Corp.
Protection
Amplifier Prefilter
7 NI 9225E Operating Instructions and Specifications
ADC
NI 9225E