Analog Input Modes And Signal Sources - National Instruments USB-6008 User Manual

+2.5 V
REF
30.9 kΩ
127 kΩ
AI
39.2 kΩ
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.

Analog Input Modes and Signal Sources

You can configure the AI channels on the NI USB-6008/6009 to take differential or referenced
single-ended (RSE) measurements. The following table summarizes the recommended analog
input mode(s) for floating signal sources and ground-references signal sources. Refer to the
table in the Pinout and Signal Descriptions
configurations for single-ended or differential measurements.
12 | ni.com | NI USB-6008/6009 User Guide
Figure 7. NI USB-6008/6009 Analog Input Circuitry
MUX PGA
Input Range
Selection
section for more information about I/O
ADC AI FIFO