National Instruments Data Acquisition Device E Series - Manual (Page 6)

Contents
E Series User Manual viii ni.com
Chapter 2
Analog Input
Analog Input Circuitry .................................................................................................. 2-1
Mux ................................................................................................................. 2-1
Instrumentation Amplifier (NI-PGIA) ............................................................ 2-2
A/D Converter................................................................................................. 2-2
AI FIFO........................................................................................................... 2-2
Analog Trigger ................................................................................................ 2-2
AI Timing Signals ........................................................................................... 2-2
Input Polarity and Range ............................................................................................... 2-2
Analog Input Terminal Configuration........................................................................... 2-5
Dither ............................................................................................................................. 2-8
Multichannel Scanning Considerations ......................................................................... 2-9
Use Low Impedance Sources .......................................................................... 2-10
Use Short High-Quality Cabling..................................................................... 2-11
Carefully Choose the Channel Scanning Order .............................................. 2-11
Avoid Switching from a Large to a Small Input Range ................... 2-11
Insert Grounded Channel between Signal Channels ........................ 2-11
Minimize Voltage Step between Adjacent Channels ....................... 2-12
Avoid Scanning Faster than Necessary........................................................... 2-12
Example 1 ......................................................................................... 2-12
Example 2 ......................................................................................... 2-13
AI Data Acquisition Methods ......................................................................... 2-13
Software-Timed Acquisitions........................................................... 2-13
Hardware-Timed Acquisitions ......................................................... 2-13
Analog Input Triggering................................................................................................ 2-14
AI Start Trigger Signal.................................................................................... 2-15
Using a Digital Source...................................................................... 2-15
Using an Analog Source ................................................................... 2-15
Outputting the AI Start Trigger Signal ........................................................... 2-16
AI Reference Trigger Signal ........................................................................... 2-16
Using a Digital Source...................................................................... 2-18
Using an Analog Source ................................................................... 2-18
Outputting the AI Reference Trigger Signal .................................... 2-18
AI Pause Trigger Signal .................................................................................. 2-19
Using a Digital Source...................................................................... 2-19
Using an Analog Source ................................................................... 2-19
Connecting Analog Input Signals.................................................................................. 2-20
Types of Signal Sources.................................................................................. 2-22
Floating Signal Sources .................................................................... 2-22
Ground-Referenced Signal Sources.................................................. 2-22