National Instruments 6008 - Manual (Page 13)

© National Instruments Corporation 13 NI USB-6008/6009 User Guide and Specifications
PGA
The progammable-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.
A/D Converter
The analog-to-digital converter (ADC) digitizes the AI signal by
converting the analog voltage into a digital code.
AI FIFO
The NI USB-6008/6009 can perform both single and multiple A/D
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
You can configure the AI channels on the NI USB-6008/6009 to take
single-ended or differential measurements. Refer to Table 5 for more
information about I/O connections for single-ended or differential
measurements.
Connecting Differential Voltage Signals
For differential signals, connect the positive lead of the signal to the AI
+
terminal, and the negative lead to the AI– terminal.
Figure 7. Connecting a Differential Voltage Signal
AI+
Voltage
Source
NI USB-6008/6009
AI–