National Instruments NI USB-621x - Page 9

Contents
© National Instruments Corporation ix NI USB-621x User Manual
Pulse-Width Measurement ..............................................................................9-5
Single Pulse-Width Measurement.....................................................9-5
Buffered Pulse-Width Measurement.................................................9-5
Period Measurement........................................................................................9-6
Single Period Measurement ..............................................................9-7
Buffered Period Measurement ..........................................................9-7
Semi-Period Measurement ..............................................................................9-9
Single Semi-Period Measurement.....................................................9-9
Buffered Semi-Period Measurement.................................................9-9
Frequency Measurement .................................................................................9-10
Method 1—Measure Low Frequency with One Counter..................9-10
Method 1b—Measure Low Frequency with One Counter
(Averaged)......................................................................................9-11
Method 2—Measure High Frequency with Two Counters...............9-11
Method 3—Measure Large Range of Frequencies Using
Two Counters .................................................................................9-12
Choosing a Method for Measuring Frequency .................................9-13
Position Measurement .....................................................................................9-15
Measurements Using Quadrature Encoders......................................9-15
Measurements Using Two Pulse Encoders.......................................9-17
Two-Signal Edge-Separation Measurement....................................................9-18
Single Two-Signal Edge-Separation Measurement ..........................9-18
Buffered Two-Signal Edge-Separation Measurement ......................9-19
Counter Output Applications .........................................................................................9-20
Simple Pulse Generation .................................................................................9-20
Single Pulse Generation ....................................................................9-20
Single Pulse Generation with Start Trigger ......................................9-20
Retriggerable Single Pulse Generation .............................................9-21
Pulse Train Generation ....................................................................................9-22
Continuous Pulse Train Generation ..................................................9-22
Frequency Generation .....................................................................................9-23
Using the Frequency Generator ........................................................9-23
Frequency Division .........................................................................................9-24
Pulse Generation for ETS................................................................................9-24
Counter Timing Signals .................................................................................................9-25
Counter n Source Signal..................................................................................9-26
Routing a Signal to Counter n Source...............................................9-26
Routing Counter n Source to an Output Terminal ............................9-26
Counter n Gate Signal .....................................................................................9-27
Routing a Signal to Counter n Gate ..................................................9-27
Routing Counter n Gate to an Output Terminal................................9-27
Counter n Aux Signal ......................................................................................9-27
Routing a Signal to Counter n Aux...................................................9-27