Contents
NI 6238/6239 User Manual vi ni.com
Chapter 4Analog Input
Analog Input Circuitry..................................................................................................4-1
Analog Input Range.......................................................................................................4-2
Connecting Analog Current Input Signals....................................................................4-3
Method 1.........................................................................................................4-3
Method 2.........................................................................................................4-4
Analog Input Ground-Reference Settings.....................................................................4-5
Configuring AI Ground-Reference Settings in Software................. 4-7
Multichannel Scanning Considerations.........................................................................4-8
Use Short High-Quality Cabling.....................................................................4-8
Minimize Current Step between Adjacent Channels......................................4-8
Avoid Scanning Faster Than Necessary.........................................................4-9
Example 1.........................................................................................4-9
Example 2.........................................................................................4-9
Analog Input Data Acquisition Methods.......................................................................4-10
Software-Timed Acquisitions.........................................................................4-10
Hardware-Timed Acquisitions........................................................................4-10
Buffered............................................................................................4-10
Non-Buffered....................................................................................4-11
Analog Input Triggering................................................................................................4-11
Field Wiring Considerations..........................................................................................4-11
Analog Input Timing Signals........................................................................................4-12
AI Sample Clock Signal..................................................................................4-15
Using an Internal Source..................................................................4-16
Using an External Source.................................................................4-16
Routing AI Sample Clock Signal to an Output Terminal.................4-16
Other Timing Requirements.............................................................4-17
AI Sample Clock Timebase Signal.................................................................4-17
AI Convert Clock Signal.................................................................................4-18
Using an Internal Source..................................................................4-18
Using an External Source.................................................................4-19
Routing AI Convert Clock Signal to an Output Terminal................4-19
Using a Delay from Sample Clock to Convert Clock...................... 4-19
Other Timing Requirements.............................................................4-20
AI Convert Clock Timebase Signal................................................................4-21
AI Hold Complete Event Signal.....................................................................4-21
AI Start Trigger Signal....................................................................................4-22
Using a Digital Source......................................................................4-22
Routing AI Start Trigger to an Output Terminal..............................4-22
AI Reference Trigger Signal...........................................................................4-23
Using a Digital Source......................................................................4-24
Routing AI Reference Trigger Signal to an Output Terminal..........4-24