National Instruments USB-621 Series User Manual

Contents
© National Instruments Corporation ix NI USB-621x User Manual
Chapter 8
Counters
Counter Input Applications............................................................................................8-2
Counting Edges ...............................................................................................8-2
Single Point (On-Demand) Edge Counting ......................................8-2
Buffered (Sample Clock) Edge Counting .........................................8-3
Controlling the Direction of Counting ..............................................8-4
Pulse-Width Measurement ..............................................................................8-4
Single Pulse-Width Measurement.....................................................8-4
Buffered Pulse-Width Measurement.................................................8-5
Period Measurement........................................................................................8-6
Single Period Measurement ..............................................................8-6
Buffered Period Measurement ..........................................................8-7
Semi-Period Measurement ..............................................................................8-8
Single Semi-Period Measurement.....................................................8-8
Buffered Semi-Period Measurement.................................................8-9
Frequency Measurement .................................................................................8-10
Choosing a Method for Measuring Frequency .................................8-14
Position Measurement .....................................................................................8-15
Measurements Using Quadrature Encoders ......................................8-16
Measurements Using Two Pulse Encoders .......................................8-18
Buffered (Sample Clock) Position Measurement .............................8-18
Two-Signal Edge-Separation Measurement....................................................8-19
Single Two-Signal Edge-Separation Measurement ..........................8-20
Buffered Two-Signal Edge-Separation Measurement ......................8-20
Counter Output Applications
...
......................................................................................8-21
Simple Pulse Generation .................................................................................8-21
Single Pulse Generation ....................................................................8-21
Single Pulse Generation with Start Trigger ......................................8-22
Retriggerable Single Pulse Generation .............................................8-22
Pulse Train Generation ....................................................................................8-23
Continuous Pulse Train Generation ..................................................8-23
Finite Pulse Train Generation ...........................................................8-24
Frequency Generation .....................................................................................8-25
Using the Frequency Generator ........................................................8-25
Frequency Division .........................................................................................8-26
Pulse Generation for ETS................................................................................8-26
Counter Timing Signals .................................................................................................8-27
Counter n Source Signal..................................................................................8-28
Routing a Signal to Counter n Source...............................................8-28
Routing Counter n Source to an Output Terminal ............................8-28

National Instruments USB-621 Series Specifications

General

Brand	National Instruments
Model	USB-621 Series
Category	Measuring Instruments
Language	English