The NI USB-6008/6009 has eight analog input channels that you can use for four differential analog input measurements or eight single-ended analog input measurements.

The following figure shows the analog input circuitry of the NI USB-6008/6009.

The main blocks featured in the NI USB-6008/6009 analog input circuitry are as follows:

• MUX—The NI USB-6008/6009 has one analog-to-digital converter (ADC). The multiplexer (MUX) routes one AI channel at a time to the PGA.
• PGA—The programmable-gain amplifier provides input gains of 1, 2, 4, 5, 8, 10, 16, or 20 when configured for differential measurements and gain of 1 when configured for single-ended measurements. The PGA gain is automatically calculated based on the voltage range selected in the measurement application.
• ADC—The analog-to-digital converter (ADC) digitizes the AI signal by converting the analog voltage into digital code.
• AI FIFO—The NI USB-6008/6009 can perform both single and multiple analog-to-digital conversions of a fixed or infinite number of samples. A first-in-first-out (FIFO) buffer holds data during AI acquisitions to ensure that no data is lost.