National Instruments 9201, 9221 operating instructions - page 9

© National Instruments Corp. 9 NI 9201/9221
The NI 9201/9221 with screw terminal has a 10-terminal,
detachable screw-terminal connector. The NI 9201/9221 with
DSUB has a 25-pin DSUB connector. Each channel has an AI
terminal or pin to which you can connect a voltage signal. COM,
the common terminal or pin, is internally connected to the isolated
ground reference of the module.
The NI 9201/9221 channels are isolated from other modules in the
system. The module protects each channel from overvoltages.
Refer to the Specifications section for more information about
overvoltage protection. The input signals are scanned, buffered,
conditioned, and then sampled by a single 12-bit ADC. Refer to
Figure3 for an illustration of the input circuitry on the
NI9201/9221.
Figure 3. Input Circuitry on the NI 9201/9221
NI 9201/9221
Buffer Isolated
ADC
Overvoltage
Protection Mux
COM
AI7
AI0