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National Instruments NI USB-621x User Manual

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NI USB-621x User Manual
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NI USB-621x User Manual
August 2006
371931A-01

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Summary of Contents for National Instruments NI USB-621x

  • Page 1 DAQ M Series NI USB-621x User Manual Bus-Powered M Series USB Devices NI USB-621x User Manual August 2006 371931A-01...
  • Page 2 Thailand 662 278 6777, United Kingdom 44 0 1635 523545 For further support information, refer to the Technical Support and Professional Services appendix. To comment on National Instruments documentation, refer to the National Instruments Web site at and enter ni.com/info the info code feedback ©...

  • Page 3: Important Information

    Instruments Corporation. National Instruments respects the intellectual property of others, and we ask our users to do the same. NI software is protected by copyright and other intellectual property laws. Where NI software may be used to reproduce software or other materials belonging to others, you may use NI software only to reproduce materials that you may reproduce in accordance with the terms of any applicable license or other legal restriction.
  • Page 4 NATIONAL INSTRUMENTS PRODUCTS ARE INCORPORATED IN A SYSTEM OR APPLICATION, INCLUDING, WITHOUT LIMITATION, THE APPROPRIATE DESIGN, PROCESS AND SAFETY LEVEL OF SUCH SYSTEM OR APPLICATION.

  • Page 5: Table Of Contents

    Programming Devices in Software ...2-4 Chapter 3 Connector Information I/O Connector Signal Descriptions ...3-1 +5 V Power ...3-2 +5 V Power as an Output ...3-2 +5 V Power as an Input ...3-3 © National Instruments Corporation NI USB-621x User Manual...
  • Page 6 Using a Digital Source... 4-21 Routing AI Start Trigger to an Output Terminal ... 4-21 AI Reference Trigger Signal ... 4-22 Using a Digital Source... 4-23 Routing AI Reference Trigger Signal to an Output Terminal ... 4-23 NI USB-621x User Manual ni.com...
  • Page 7 Using Non-Referenced Single-Ended (NRSE) Connections for Ground-Referenced Signal Sources...5-13 Chapter 6 Connecting AI Signals on the USB-6215/6218 Devices Differential Measurements ...6-1 Differential Pairs...6-1 Referenced Single-Ended (RSE) Measurements ...6-3 Non-Referenced Single-Ended (NRSE) Measurements ...6-4 © National Instruments Corporation Contents NI USB-621x User Manual...
  • Page 8 Counter Input Applications ... 9-2 Counting Edges ... 9-2 Single Point (On-Demand) Edge Counting ... 9-2 Buffered (Sample Clock) Edge Counting... 9-3 Non-Cumulative Buffered Edge Counting ... 9-4 Controlling the Direction of Counting... 9-4 NI USB-621x User Manual viii ni.com...
  • Page 9 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 © National Instruments Corporation Contents NI USB-621x User Manual...
  • Page 10 Using PFI Terminals as Timing Input Signals ... 10-2 Exporting Timing Output Signals Using PFI Terminals... 10-3 Using PFI Terminals as Static Digital I/Os ... 10-3 Connecting PFI Input Signals... 10-3 PFI Filters ... 10-4 I/O Protection ... 10-6 Programmable Power-Up States... 10-6 NI USB-621x User Manual ni.com...
  • Page 11 Data Transfer Methods ...13-1 USB Signal Stream...13-1 Programmed I/O ...13-2 Changing Data Transfer Methods ...13-2 Chapter 14 Triggering Triggering with a Digital Source ...14-1 Appendix A Device-Specific Information USB-6210 ...A-1 USB-6211/6215 ...A-4 USB 6218...A-7 © National Instruments Corporation Contents NI USB-621x User Manual...
  • Page 12 Contents Appendix B Troubleshooting Appendix C Technical Support and Professional Services Glossary Index Device Pinouts Figure A-1. USB-6210 Pinout ... A-2 Figure A-2. USB-6211/6215 Pinout ... A-5 Figure A-3. USB 6218 Pinout ... A-8 NI USB-621x User Manual ni.com...

  • Page 13: About This Manual

    This font is also used for the proper names of disk drives, paths, directories, programs, subprograms, subroutines, device names, functions, operations, variables, filenames, and extensions. © National Instruments Corporation ni.com/manuals xiii , for NI USB-621x User Manual...

  • Page 14: Related Documentation

    NI-DAQmx for Windows software, your NI-DAQmx-supported DAQ device, and how to confirm that your device is operating properly. Select Start»All Programs»National Instruments» NI-DAQ»NI-DAQmx for USB Devices Getting Started. The NI-DAQ Readme lists which devices are supported by this version of NI-DAQ.

  • Page 15: Labwindows™/Cvi

    Functions—Describes the LabVIEW NI-DAQmx VIs and properties. Taking Measurements—Contains the conceptual and how-to information you need to acquire and analyze measurement data in LabVIEW, including common measurements, measurement fundamentals, NI-DAQmx key concepts, and device considerations. About This Manual NI USB-621x User Manual...

  • Page 16: Net Languages Without Ni Application Software

    Adobe Acrobat Reader with Search and Accessibility 5.0.5 or later installed to view the PDFs. Refer to the Adobe Systems Incorporated Web site at National Instruments Product Manuals Library at updated documentation resources. NI USB-621x User Manual ni.com/training ni.com/support...

  • Page 17: Getting Started

    Getting Started Figure 1-1. USB-6210/6211 © National Instruments Corporation NI USB-621x User Manual...

  • Page 18: Installing Ni-Daqmx

    Installing Other Software If you are using other software, refer to the installation instructions that accompany your software. NI USB-621x User Manual Figure 1-2. USB-6215/6218 , offers NI-DAQmx users step-by-step ni.com/manuals ni.com...

  • Page 19: Installing The Hardware

    NI offers a variety of accessories to use with your DAQ device. Refer to Appendix A, information. © National Instruments Corporation Device-Specific Information, for NI 621x device , for more detailed information ni.com/manuals Device-Specific Information, or Chapter 1 Getting Started for more ni.com NI USB-621x User Manual...

  • Page 20: Daq System Overview

    I/O signals. Figure 2-2 features components common to all USB M Series devices. © National Instruments Corporation Hardware Software Figure 2-1. Components of a Typical DAQ System Personal Computer or Laptop NI USB-621x User Manual...

  • Page 21: Daq-Stc2

    You can calibrate the device to minimize AI and AO errors caused by time and temperature drift at run time. No external circuitry is necessary; an internal reference ensures high accuracy and stability over time and temperature changes. NI USB-621x User Manual Isolation Barrier (USB-6215...

  • Page 22: Signal Conditioning

    Help»Search the LabVIEW Help in LabVIEW and then navigate to the Taking Measurements book on the Contents tab. If you are using other application software, refer to Common Sensors in the NI-DAQmx Help or the LabVIEW 8.x Help. Chapter 2 DAQ System Overview ni.com/sensors NI USB-621x User Manual...

  • Page 23: Programming Devices In Software

    Chapter 2 DAQ System Overview Programming Devices in Software National Instruments measurement devices are packaged with NI-DAQ driver software, an extensive library of functions and VIs you can call from your application software, such as LabVIEW or LabWindows/CVI, to program all the features of your NI measurement devices. Driver software...

  • Page 24: Connector Information

    Analog Input Sense—In NRSE mode, the reference for each AI <0..31> signal is AI SENSE. Output Analog Output Channels 0 to 1—These terminals supply the voltage output of AO channels 0 to 1. +5 V Power sections contain Description NI USB-621x User Manual...

  • Page 25: +5 V Power

    PFI <4..7> and PFI <12..15>/P1.<0..7>. The USB-621x monitors the total current and will drop the voltage on all of the digital outputs and the +5 V terminals if the 50 mA limit is exceeded. NI USB-621x User Manual Table 3-1. I/O Connector Signals (Continued) Direction —...

  • Page 26: +5 V Power As An Input

    If your USB-621x device has more than one +5 V terminal, you can connect the external power supply to one terminal and use the other as a power source. © National Instruments Corporation Chapter 3 Connector Information NI USB-621x User Manual...

  • Page 27: Analog Input

    AI FIFO Input Range Selection Figure 4-1. M Series Analog Input Circuitry section. Also refer to Appendix A, Information, for device I/O connector pinouts. Isolation Barrier (USB-6215 and USB-6218 devices only) Digital AI Data Isolators Analog Input NI USB-621x User Manual...

  • Page 28: Analog Input Range

    M Series devices use a calibration method that requires some codes (typically about 5% of the codes) to lie outside of the specified range. This NI USB-621x User Manual ) codes—that is, one of 65,536 possible digital values. So, for (10 V –...

  • Page 29: Analog Input Ground-Reference Settings

    AI signal relative to the AI SENSE input. © National Instruments Corporation Table 4-1. Input Ranges for NI 621x Nominal Resolution Assuming Input Range 320 μV 160 μV 32 μV 6.4 μV Description Chapter 4 Analog Input 5% Over Range NI USB-621x User Manual...

  • Page 30: Figure

    AI <0..7> AI <16..23> For differential measurements, AI 0 and AI 8 are the positive and negative inputs of differential analog input channel 0. For a complete list of signal NI USB-621x User Manual Devices, section for more information. PGIA in–...

  • Page 31: Configuring Ai Ground-Reference Settings In Software

    © National Instruments Corporation section of Chapter 3, Connector of the NI-DAQmx API. You must use a new VI for Figure 4-3. Enabling Multimode Scanning in LabVIEW Chapter 4 Analog Input I/O Connector Signal Information. NI-DAQmx Create NI USB-621x User Manual...

  • Page 32: Multichannel Scanning Considerations

    1 is high enough, the resulting reading of channel 1 can be partially affected by the voltage on channel 0. This effect is referred to as ghosting. NI USB-621x User Manual Use low impedance sources Use short high-quality cabling...

  • Page 33: Carefully Choose The Channel Scanning Order

    0 is –10 V to 10 V and the input range of channel 1 is –200 mV to 200 mV. © National Instruments Corporation and entering the info code ni.com/info Chapter 4 Analog Input rdbbis NI USB-621x User Manual...

  • Page 34: Minimize Voltage Step Between Adjacent Channels

    However, doubling the number of samples (in this example) decreases the time the NI-PGIA has to settle from 8 µs to 4 µs. In some cases, the slower scan rate system returns more accurate results. NI USB-621x User Manual ni.com...

  • Page 35: Example 2

    • Hardware-timed operations can be buffered or non-buffered. © National Instruments Corporation The time between samples can be much shorter. The timing between samples is deterministic. Hardware-timed acquisitions can use hardware triggering. Chapter 4 Analog Input NI USB-621x User Manual...

  • Page 36: Buffered

    Analog Input Digital Triggering Analog input supports three different triggering actions: • • • Refer to the Pause Trigger Signal NI USB-621x User Manual Start trigger Reference trigger Pause trigger AI Start Trigger Signal, sections for information about these triggers.

  • Page 37: Field Wiring Considerations

    You then connect this shield only at one point to the signal source ground. This kind of connection is required for signals traveling through areas with large magnetic fields or high electromagnetic interference. and enter the info code ni.com/info 4-11 Chapter 4 Analog Input rdfwn3 NI USB-621x User Manual...
  • Page 38 As Figure 4-5 shows, ai/SampleClock controls the sample period, which is determined by the following equation: ai/ConvertClock controls the Convert Period, which is determined by the following equation: NI USB-621x User Manual Analog Comparison Event Ctr n Internal Output Timebase...
  • Page 39 The sample counter is then loaded with the number of posttriggered samples, in this example, three. © National Instruments Corporation ai/StartTrigger Figure 4-6. Posttriggered Data Acquisition Example 4-13 Chapter 4 NI USB-621x User Manual Analog Input...

  • Page 40: Ai Sample Clock Signal

    You can specify an internal or external source for ai/SampleClock. You also can specify whether the measurement sample begins on the rising edge or falling edge of ai/SampleClock. NI USB-621x User Manual ai/StartTrigger ai/SampleClock ai/ConvertClock Scan Counter Figure 4-7.

  • Page 41: Using An Internal Source

    Failure to do so may result in ai/SampleClock pulses that are masked off and acquisitions with erratic sampling intervals. Refer © National Instruments Corporation Counter n Internal Output AI Sample Clock Timebase (divided down) A software pulse 4-15 Chapter 4 Analog Input NI USB-621x User Manual...

  • Page 42: Ai Sample Clock Timebase Signal

    By default, NI-DAQmx chooses the fastest conversion rate possible based on the speed of the A/D converter and adds 10 µs of padding between each NI USB-621x User Manual ai/SampleClockTimebase ai/StartTrigger ai/SampleClock Figure 4-8.

  • Page 43: Using An Internal Source

    By default, this delay is three ticks of ai/ConvertClockTimebase. © National Instruments Corporation AI Convert Clock Timebase (divided down) Counter n Internal Output 4-17 Chapter 4 Analog Input NI USB-621x User Manual...

  • Page 44: Other Timing Requirements

    Figures 4-10, 4-11, 4-12, and 4-13 show timing sequences for a four-channel acquisition (using AI channels 0, 1, 2, and 3) and demonstrate proper and improper sequencing of ai/SampleClock and ai/ConvertClock. NI USB-621x User Manual Delay Convert From...
  • Page 45 Figure 4-12. ai/SampleClock and ai/ConvertClock Improperly Matched 4-19 Chapter 4 Analog Input 1 2 3 1 2 3 Sample #2 Sample #3 1 2 3 1 2 3 Sample #2 Sample #3 Sample #2 Sample #3 NI USB-621x User Manual...

  • Page 46: Ai Convert Clock Timebase Signal

    Use one of the following signals as the source of ai/ConvertClockTimebase: • • ai/ConvertClockTimebase is not available as an output on the I/O connector. NI USB-621x User Manual ai/SampleClock ai/ConvertClock 1 2 3 Sample #1 • Properly Matched Sample Clock and Convert Clock Figure 4-13.

  • Page 47: Ai Hold Complete Event Signal

    When a certain number of points are sampled (in finite mode) After a hardware reference trigger (in finite mode) With a software command (in continuous mode) PFI <0..3>, PFI <8..11> Counter n Internal Output 4-21 Chapter 4 Analog Input NI USB-621x User Manual...

  • Page 48: Ai Reference Trigger Signal

    When the reference trigger occurs, the DAQ device continues to write samples to the buffer until the buffer contains the number of posttrigger samples desired. Figure 4-15 shows the final buffer. NI USB-621x User Manual and enter the info code Reference Trigger...

  • Page 49: Using A Digital Source

    The source also can be one of several other internal signals on your DAQ device. Refer to Device Routing in MAX in the NI-DAQmx Help or the LabVIEW 8.x Help for more information. © National Instruments Corporation 4-23 Chapter 4 Analog Input NI USB-621x User Manual...

  • Page 50: Getting Started With Ai Applications In Software

    Note For more information about programming analog input applications and triggers in software, refer to the NI-DAQmx Help or the LabVIEW 8.x Help. NI USB-621x User Manual Single-point analog input Finite analog input Continuous analog input 4-24 ni.com...

  • Page 51: Connecting Ai Signals On The Usb-6210/6211 Devices

    Connecting AI Signals on the USB-6210/6211 Devices Table 5-1 summarizes the recommended input configuration for both types of signal sources on NI 6210/6211 devices. © National Instruments Corporation NI USB-621x User Manual...
  • Page 52 Signal Source Referenced (RSE) Refer to the Analog Input Ground-Reference Settings NRSE, and DIFF modes and software considerations. Refer to the Connecting Ground-Referenced Signal Sources NI USB-621x User Manual Table 5-1. Analog Input Configuration DAQ Device AI– – – AI GND DAQ Device –...

  • Page 53: Connecting Floating Signal Sources

    The input signal can share a common reference point, AI GND, with other signals that use RSE. The input signal is high-level (greater than 1 V). The leads connecting the signal to the device are less than 3 m (10 ft). NI USB-621x User Manual...

  • Page 54: When To Use Non-Referenced Single-Ended (Nrse) Connections With Floating Signal Sources

    Refer to the Floating Signal Sources connections. NI USB-621x User Manual Using Referenced Single-Ended (RSE) Connections for section for more information about RSE The input signal is high-level (greater than 1 V). The leads connecting the signal to the device are less than 3 m (10 ft).

  • Page 55: Using Differential Connections For Floating Signal Sources

    (other than the very high input impedance of the NI-PGIA). © National Instruments Corporation Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices Floating Signal Source – Inpedance <100 Ω AI– AI SENSE AI GND NI USB-621x User Manual...
  • Page 56 (sum) of the two resistors. If, for example, the source impedance is 2 kΩ and each of the two resistors is 100 kΩ, the resistors load down the source with 200 kΩ and produce a –1% gain error. NI USB-621x User Manual Floating Signal Source –...
  • Page 57 © National Instruments Corporation Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices AI– Input Multiplexers AI SENSE AI GND M Series Device Configured in DIFF Mode Resistors Instrumentation Amplifier PGIA Measured – Voltage – NI USB-621x User Manual...

  • Page 58: Using Non-Referenced Single-Ended (Nrse) Connections For Floating Signal Sources

    NRSE mode is better than RSE mode because the AI SENSE connection is made remotely near the source. However, the noise rejection of NRSE mode is worse than DIFF mode because the AI SENSE NI USB-621x User Manual AC Coupling AC Coupled...

  • Page 59: Using Referenced Single-Ended (Rse) Connections For Floating Signal Sources

    Figure 5-6. RSE Connections for Floating Signal Sources Configuring AI Ground-Reference Settings in section of Chapter 4, Analog Input, for more information about Programmable Gain Instrumentation Amplifier PGIA Measured – Voltage – Input, for more information about NI USB-621x User Manual...

  • Page 60: When To Use Differential Connections With Ground-Referenced Signal Sources

    DIFF input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions. NI USB-621x User Manual The input signal is low level (less than 1 V). The leads connecting the signal to the device are greater than 3 m (10 ft).

  • Page 61: When To Use Referenced Single-Ended (Rse) Connections With Ground-Referenced Signal Sources

    AI GND and the ground of the sensor. In RSE mode, this ground loop causes measurement errors. © National Instruments Corporation Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices Using Non-Referenced Single-Ended (NRSE) Connections for section for more information about 5-11 NI USB-621x User Manual...

  • Page 62: Using Differential Connections For Ground-Referenced Signal Sources

    With this type of connection, the NI-PGIA rejects both the common-mode noise in the signal and the ground potential difference between the signal source and the device ground, shown as V AI+ and AI– must both remain within ±11 V of AI GND. NI USB-621x User Manual Ground- Signal –...

  • Page 63: Using Non-Referenced Single-Ended (Nrse) Connections For Ground-Referenced Signal Sources

    AI SENSE AI GND M Series Device Configured in NRSE Mode (NRSE Configuration) Configuring AI Ground-Reference Settings in section of Chapter 4, Analog Input, for more information about 5-13 Instrumentation Amplifier PGIA Measured – Voltage – NI USB-621x User Manual...

  • Page 64: Connecting Ai Signals On The Usb-6215/6218 Devices

    Table 6-1 the signal pairs that are valid for differential connection configurations with the USB-6215/6218. © National Instruments Corporation Table 6-1. I/O Connector Signals Channel Signal + AI 0 AI 1 AI 2 Signal – AI 8 AI 9 AI 10 NI USB-621x User Manual...
  • Page 65 * USB-6218 devices only. Refer to Figure 6-1 for an illustration of a differential connection configuration. Figure 6-1. Connecting a Device to a USB-6215/6218 Using Differential Connections NI USB-621x User Manual Table 6-1. I/O Connector Signals (Continued) Channel Signal +...

  • Page 66: Referenced Single-Ended (Rse) Measurements

    In an RSE connection configuration, each input channel is measured with respect to AI GND. © National Instruments Corporation Chapter 6 Connecting AI Signals on the USB-6215/6218 Devices , to be rejected during the measurement of V AI GND PGIA USB-6215/6218 NI USB-621x User Manual...

  • Page 67: Non-Referenced Single-Ended (Nrse) Measurements

    Refer to Figure 6-3 for an illustration of an NRSE connection configuration. Figure 6-3. Connecting a Device to a USB-6215/6218 Using NRSE Connections In the NRSE connection configuration, each input channel is measured with respect to AI SENSE. NI USB-621x User Manual PGIA AISENSE AI GND USB-6215/6218...

  • Page 68: Analog Output

    (FIFO) memory buffer between the computer and the © National Instruments Corporation Information, for information about the capabilities of your Isolation Barrier (USB-6215 and USB-6218 devices only) Digital AO FIFO Isolators AO Sample Clock Figure 7-1. M Series Analog Output Circuitry AO Data NI USB-621x User Manual...

  • Page 69: Ao Range

    DC voltage. Hardware-Timed Generations With a hardware-timed generation, a digital hardware signal controls the rate of the generation. This signal can be generated internally on your device or provided externally. NI USB-621x User Manual for more information about minimizing glitches. ni.com...
  • Page 70 If the program does not write new data to © National Instruments Corporation The time between samples can be much shorter. The timing between samples can be deterministic. Hardware-timed acquisitions can use hardware triggering. Chapter 7 Analog Output NI USB-621x User Manual...

  • Page 71: Analog Output Digital Triggering

    AO <0..1> are the voltage output signals for AO channels 0 and 1. AO GND is the ground reference for AO <0..1>. Figure 7-2 shows how to make AO connections to the device. Load Load NI USB-621x User Manual Start trigger Pause trigger AO Start Trigger Signal Analog Output Channels...

  • Page 72: Analog Output Timing Signals

    Figure 7-3. Analog Output Timing Options AO Start Trigger Signal AO Pause Trigger Signal AO Sample Clock Signal AO Sample Clock Timebase Signal A software pulse PFI <0..3>, PFI <8..11> ai/StartTrigger Chapter 7 Analog Output ao/SampleClock NI USB-621x User Manual...

  • Page 73: Routing Ao Start Trigger Signal To An Output Terminal

    Figure 7-4. Using a Digital Source To use ao/PauseTrigger, specify a source and a polarity. The source can be the PFI <0..3> or PFI <8..11> signals. NI USB-621x User Manual Pause Trigger Sample Clock Figure 7-4. ao/PauseTrigger with Other Signal Source...

  • Page 74: Ao Sample Clock Signal

    By default, this delay is two ticks of ao/SampleClockTimebase. © National Instruments Corporation AO Sample Clock Timebase (divided down) Counter n Internal Output Chapter 7 Analog Output NI USB-621x User Manual...

  • Page 75: Ao Sample Clock Timebase Signal

    If you want to use an external sample clock signal, but do not need to divide the signal, then you should use ao/SampleClock rather than ao/SampleClockTimebase. NI USB-621x User Manual ao/SampleClockTimebase ao/StartTrigger ao/SampleClock Figure 7-5.

  • Page 76: Getting Started With Ao Applications In Software

    Note For more information about programming analog output applications and triggers in software, refer to the NI-DAQmx Help or the LabVIEW 8.x Help. © National Instruments Corporation Single-point (on-demand) generation Finite generation Continuous generation Waveform generation Chapter 7 Analog Output NI USB-621x User Manual...

  • Page 77: Digital I/O

    Export a timing output signal to a line as a PFI pin Static DI Static DO Figure 8-1. M Series Digital I/O Circuitry P0. x I/O Protection 47kΩ Pull-Down P1. x I/O Protection 47 kΩ Pull-Down NI USB-621x User Manual...

  • Page 78: Static Dio

    +5 V terminals is 50 mA. You can increase this internal current limit by supplying an external +5 V supply. Refer to the section of Chapter 3, NI USB-621x User Manual Do not connect a DO or PFI output lines to any external signal source, ground signal, or power supply.

  • Page 79: Connecting Digital I/O Signals

    © National Instruments Corporation P1.<0..3> P0.<0..3> D GND M Series Device and/or AI GND to the local ground on your system. Figure 8-2. Digital I/O Connections Chapter 8 Digital I/O Isolation Barrier (USB-6215 and USB-6218 devices only) Digital Isolators NI USB-621x User Manual...

  • Page 80: Getting Started With Dio Applications In Software

    • • Note For more information about programming digital I/O applications and triggers in software, refer to the NI-DAQmx Help or the LabVIEW 8.x Help. NI USB-621x User Manual Static digital input Static digital output Digital waveform generation Digital waveform acquisition DI change detection ni.com...

  • Page 81: Counters

    Counter 1 Aux Counter 1 HW Arm Counter 1 A Counter 1 B (Counter 1 Up_Down) Counter 1 Z Frequency Generator Frequency Output Timebase Figure 9-1. M Series Counters Counter 0 TC Counter 0 TC Freq Out NI USB-621x User Manual...

  • Page 82: Counter Input Applications

    You can route the pause trigger to the Gate input of the counter. You can configure the counter to pause counting when the pause trigger is high or when it is low. Figure 9-3 shows an example of on-demand edge counting with a pause trigger. NI USB-621x User Manual section. Counter Armed SOURCE Counter Value Figure 9-2.

  • Page 83: Buffered (Sample Clock) Edge Counting

    (Pause When Low) SOURCE Counter Value Figure 9-3. Single Point (On-Demand) Edge Counting with Pause Trigger Counter Armed Sample Clock (Sample on Rising Edge) SOURCE Counter Value Buffer Figure 9-4. Buffered (Sample Clock) Edge Counting Chapter 9 NI USB-621x User Manual Counters...

  • Page 84: Non-Cumulative Buffered Edge Counting

    In edge counting applications, the counter can count up or down. You can configure the counter to do the following: • • • For information about connecting counter signals, refer to the Counter/Timer Pinouts NI USB-621x User Manual Counter Armed Sample Clock (Sample on Rising Edge) SOURCE...

  • Page 85: Pulse-Width Measurement

    Buffered Pulse-Width Measurement Buffered pulse-width measurement is similar to single pulse-width measurement, but buffered pulse-width measurement takes measurements over multiple pulses. © National Instruments Corporation GATE SOURCE Counter Value Figure 9-6. Single Pulse-Width Measurement Chapter 9 Counters NI USB-621x User Manual...

  • Page 86: Period Measurement

    Gate signal. You can calculate the period of the Gate input by multiplying the period of the Source signal by the number of edges returned by the counter. NI USB-621x User Manual Figure 9-7. Buffered Pulse-Width Measurement Duplicate Count Prevention section.

  • Page 87: Single Period Measurement

    Gate input. The counter does not store a measurement for this incomplete period. Figure 9-9 shows an example of a buffered period measurement. In this example, a period is defined by two consecutive rising edges. © National Instruments Corporation NI USB-621x User Manual...
  • Page 88 Refer to the Count Prevention For information about connecting counter signals, refer to the Counter/Timer Pinouts NI USB-621x User Manual Counter Armed Figure 9-9. Buffered Period Measurement Table 9-1. Time N Descriptions At t , the counter is armed.

  • Page 89: Semi-Period Measurement

    Note that if you are using an external signal as the Source, at least one Source pulse should occur between each active edge of the Gate signal. © National Instruments Corporation Counter Armed GATE SOURCE Counter Value Buffer Figure 9-10. Buffered Semi-Period Measurement Chapter 9 Counters NI USB-621x User Manual...

  • Page 90: Frequency Measurement

    0.02 Hz, use a slower known timebase. You can configure the counter to measure one period of the gate signal. The frequency of F1 is the inverse of the period. Figure 9-11 illustrates this method. NI USB-621x User Manual section for more information. section. Gate...

  • Page 91: Method 1B-Measure Low Frequency With One Counter (Averaged)

    Average Period of F1 = Frequency of F1 = Figure 9-12. Method 1b 9-11 Chapter 9 Counters Intervals Measured … 1..N … 1..N + … N × K × Ft + … N NI USB-621x User Manual...

  • Page 92: Method 3-Measure Large Range Of Frequencies Using Two Counters

    Figure 9-14. Assume this signal to measure has frequency F1. Configure Counter 0 to generate a single pulse that is the width of N periods of the source input signal. NI USB-621x User Manual Width of Pulse (T) Pulse …...

  • Page 93: Choosing A Method For Measuring Frequency

    Consider a frequency measurement on a 50 kHz signal using an 80 MHz Timebase. This frequency corresponds to 1600 cycles of the 9-13 Chapter 9 COUNTER 0 SOURCE COUNTER 1 GATE 3 … N Interval to Measure NI USB-621x User Manual Counters...
  • Page 94 • • • NI USB-621x User Manual 80 MHz Timebase. Your measurement may return 1600 ± 1 cycles depending on the phase of the signal with respect to the timebase. As your frequency becomes larger, this error of ±1 cycle becomes more significant;...

  • Page 95: Position Measurement

    X2, or X4. © National Instruments Corporation Measures High Number of Frequency Measurements Signals Returned Accurately Poor Many Fair Good Good section. 9-15 Chapter 9 Counters Measures Low Frequency Signals Accurately Good Good Poor Good Default NI USB-621x User Manual...
  • Page 96 Each cycle results in four increments or decrements, as shown in Figure 9-17. Ch A Ch B Counter Value NI USB-621x User Manual Ch A Ch B Counter Value Figure 9-15. X1 Encoding...

  • Page 97: Measurements Using Two Pulse Encoders

    A and B. © National Instruments Corporation Ch A Ch B Ch Z Max Timebase Counter Value A = 0 B = 0 Z = 1 Figure 9-18. Channel Z Reload with X4 Decoding 9-17 Chapter 9 NI USB-621x User Manual Counters...

  • Page 98: Two-Signal Edge-Separation Measurement

    Gate signal and an active edge of the Aux signal. The counter then stores the count in a hardware save register and ignores other edges on its inputs. Software then reads the stored count. NI USB-621x User Manual Ch A Ch B Figure 9-19.

  • Page 99: Buffered Two-Signal Edge-Separation Measurement

    Counter/Timer Pinouts © National Instruments Corporation Counter Armed GATE SOURCE Counter Value Figure 9-20. Single Two-Signal Edge-Separation Measurement GATE SOURCE Counter Value Buffer Figure 9-21. Buffered Two-Signal Edge-Separation Measurement section. 9-19 Chapter 9 Measured Interval Default NI USB-621x User Manual Counters...

  • Page 100: Counter Output Applications

    The delay and pulse width are measured in terms of a number of active edges of the Source input. After the Start Trigger signal pulses once, the counter ignores the Gate input. NI USB-621x User Manual Counter Armed SOURCE Figure 9-22. Single Pulse Generation 9-20 ni.com...

  • Page 101: Retriggerable Single Pulse Generation

    (using the rising edge of Source). GATE (Start Trigger) SOURCE Figure 9-24. Retriggerable Single Pulse Generation For information about connecting counter signals, refer to the Default Counter/Timer Pinouts section. © National Instruments Corporation 9-21 NI USB-621x User Manual...

  • Page 102: Pulse Train Generation

    Counter n Internal Output signal is equal to the frequency of the Source input divided by M + N. For information about connecting counter signals, refer to the Counter/Timer Pinouts NI USB-621x User Manual SOURCE Counter Armed Figure 9-25. Continuous Pulse Train Generation section.

  • Page 103: Frequency Generation

    Output Timebase FREQ OUT (Divisor = 5) © National Instruments Corporation Frequency Output Timebase Frequency Generator Divisor (1–16) Figure 9-26. Frequency Generator Block Diagram Figure 9-27. Frequency Generator Output Waveform 9-23 Chapter 9 Counters FREQ OUT NI USB-621x User Manual...

  • Page 104: Frequency Division

    The waveform thus produced at the counter’s output can be used to provide timing for undersampling applications where a digitizing system can sample repetitive waveforms that are higher in frequency than the Nyquist NI USB-621x User Manual section. section. 9-24...

  • Page 105: Counter Timing Signals

    Counter n Aux Counter n A Counter n B Counter n Z Counter n Up_Down Counter n HW Arm Counter n Internal Output Counter n TC Frequency Output 9-25 Chapter 9 Counters D3 = D1 + 2ΔD Default NI USB-621x User Manual...

  • Page 106: Counter N Source Signal

    Some of these options may not be available in some driver software. Routing Counter n Source to an Output Terminal You can route Counter n Source out to any PFI <4..7> or PFII <12..15> terminal. NI USB-621x User Manual Table 9-4. Counter Applications and Counter n Source Application 80 MHz Timebase...

  • Page 107: Counter N Gate Signal

    Counter 0 Gate can be routed to Counter 0 Aux. Counter 0 Internal © National Instruments Corporation PFI <0..3>, PFI <8..11> ai/ReferenceTrigger ai/StartTrigger ai/SampleClock ai/ConvertClock ao/SampleClock PFI <0..3>, PFI <8..11> ai/ReferenceTrigger ai/StartTrigger 9-27 Chapter 9 Counters NI USB-621x User Manual...

  • Page 108: Counter N A, Counter N B, And Counter N Z Signals

    Any of the following signals can be routed to the Counter n HW Arm input. • • • Counter 1 Internal Output can be routed to Counter 0 HW Arm. Counter 0 Internal Output can be routed to Counter 1 HW Arm. NI USB-621x User Manual PFI <0..3>, PFI <8..11> ai/ReferenceTrigger ai/StartTrigger 9-28 ni.com...

  • Page 109: Counter N Internal Output And Counter N Tc Signals

    CTR 0 A CTR 0 Z © National Instruments Corporation Default Terminal Number (Name) 1 (PFI 0) 2 (PFI 1) 1 (PFI 0) 6 (PFI 4) 1 (PFI 0) 3 (PFI 2) 9-29 Chapter 9 Counters NI USB-621x User Manual...
  • Page 110 CTR 1 AUX CTR 1 OUT CTR 1 A CTR 1 Z CTR 1 B FREQ OUT NI USB-621x User Manual Default Terminal Number (Name) 2 (PFI 1) 4 (PFI 3) 3 (PFI 2) 4 (PFI 3) 7 (PFI 5)

  • Page 111: Counter Triggering

    You can use pause triggers in edge counting and continuous pulse generation applications. For edge counting acquisitions, the counter stops counting edges while the external trigger signal is low and resumes when © National Instruments Corporation 9-31 Chapter 9 Counters NI USB-621x User Manual...

  • Page 112: Other Counter Features

    In this example, a period is defined by two consecutive rising edges of the Gate. Counter Armed GATE SOURCE COUNTER VALUE SAMPLE CLOCK BUFFER TIME N NI USB-621x User Manual Figure 9-29. Sample Clock Example 9-32 ni.com...

  • Page 113: Cascading Counters

    The value of N depends on the filter setting; refer to Table 9-8. © National Instruments Corporation Table 9-7. Time N Descriptions Method 3—Measure Large Range of section. 9-33 Chapter 9 Counters NI USB-621x User Manual...

  • Page 114: Prescaling

    Thus, the prescaler acts as a frequency divider on the Source and puts out a frequency that is one-eighth (or one-half) of what it is accepting. NI USB-621x User Manual Table 9-8. Filters Pulse Width...

  • Page 115: Duplicate Count Prevention

    Source pulses between rising edges on the Gate signal. © National Instruments Corporation External Signal Prescaler Rollover (Used as Source by Counter) Counter Value Figure 9-31. Prescaling 9-35 Chapter 9 Counters NI USB-621x User Manual...

  • Page 116: Example Application That Works Correctly (No Duplicate Counting)

    Source pulse. In this example, the counter stores the values in the buffer on the first rising Source edge after the rising edge of Gate. The details of when exactly the counter synchronizes the Gate signal vary depending on the synchronization mode. NI USB-621x User Manual Gate Source Buffer Figure 9-32.

  • Page 117: Example Application That Works Incorrectly (Duplicate Counting)

    Figure 9-33. Duplicate Count Example Counter detects rising Gate edge. Figure 9-34. Duplicate Count Prevention Example 9-37 Chapter 9 Counters No Source edge, so no value written to buffer. Counter value increments only one time for each Source pulse. NI USB-621x User Manual...

  • Page 118: Enabling Duplicate Count Prevention In Ni-Daqmx

    Counter n Internal Output signals change synchronously to the 80 MHz Timebase. Enabling Duplicate Count Prevention in NI-DAQmx Duplicate count prevention is automatically used with the USB-621x devices. Disabling duplicate count prevention is not supported. NI USB-621x User Manual 9-38 ni.com...

  • Page 119: Pfi

    A static digital output A timing output signal from AI, AO, or counter/timer functions Static DI Filters Figure 10-1. NI 621x PFI Input Circuitry 10-1 Isolation Barrier (USB-6215 and USB-6218 devices only) Digital To Input Timing Isolators Signal Selectors NI USB-621x User Manual...

  • Page 120: Using Pfi Terminals As Timing Input Signals

    • • • • • • • • • NI USB-621x User Manual Static DO Buffer Direction Control Figure 10-2. NI 621x PFI Output Circuitry AI Convert Clock AI Sample Clock AI Start Trigger AI Reference Trigger AI Pause Trigger...

  • Page 121: Exporting Timing Output Signals Using Pfi Terminals

    AI Convert Clock* AI Hold Complete Event AI Reference Trigger AI Sample Clock AI Start Trigger AO Sample Clock* AO Start Trigger Counter n Source Counter n Gate Counter n Internal Output Frequency Output 10-3 Chapter 10 NI USB-621x User Manual...

  • Page 122: Pfi Filters

    N consecutive edges, the low to high transition is propagated to the rest of the circuit. The value of N depends on the filter setting; refer to Table 10-1. NI USB-621x User Manual PFI 0 PFI 2...
  • Page 123 Guaranteed to Not Filter Pass Filter 125 ns 100 ns 6.400 µs 2.54 ms — — Filtered input goes high when terminal is sampled high on five consecutive filter clocks. and enter the info code rddfms NI USB-621x User Manual...

  • Page 124: I/O Protection

    Refer to the NI-DAQmx Help or the LabVIEW 8.x Help for more information about setting power-up states in NI-DAQmx or MAX. NI USB-621x User Manual Do not connect a DO or PFI output lines to any external signal source, ground signal, or power supply.

  • Page 125: Isolation And Digital Isolators

    © National Instruments Corporation Table 11-1. Ground Symbols Non-Isolated Ground Isolation Barrier (USB-6215 and USB-6218 devices only) Digital Routing Digital and Clock Isolators Generation Figure 11-1. General NI 621x Block Diagram 11-1 Interface NI USB-621x User Manual...

  • Page 126: Digital Isolation

    Isolated products require an isolated power supply to deliver power to the isolated side from the non-isolated side. Isolated power supplies work by switching voltages through a transformer with high-speed transistors. NI USB-621x User Manual Connecting AI Signals on the Devices, Chapter 6,...

  • Page 127: Creating An Ac Return Path

    Reduce source impedances if possible. The parasitic currents react with these impedances. 11-3 Chapter 11 Isolation and Digital Isolators NI USB-621x User Manual...
  • Page 128 Add an AC return path from the device isolated ground to earth ground. For non-isolated systems, an AC return path is only needed for high or source impedances. An AC return path can be created by connecting a capacitor between the device’s isolated ground and earth ground. NI USB-621x User Manual 11-4 ni.com...

  • Page 129: Digital Routing And Clock Generation

    These signals can come from the following sources. – Your M Series device – User input through the PFI terminals Routes and generates the main clock signals for the M Series device. 12-1 NI USB-621x User Manual...

  • Page 130: 100 Khz Timebase

    The 100 kHz Timebase also can be used as the Source input to the 32-bit general-purpose counter/timers. The 100 kHz Timebase is generated by dividing down the 20 MHz Timebase by 200. NI USB-621x User Manual 12-2 ni.com...

  • Page 131: Bus Interface

    NI device. NI uses USB Signal Stream hardware and software technology to achieve high throughput rates and increase system utilization in USB devices. © National Instruments Corporation Analog input Analog output Counter 0 Counter 1 13-1 NI USB-621x User Manual...

  • Page 132: Programmed I/O

    USB M Series devices have four dedicated USB Signal Stream channels. To change your data transfer mechanism between USB Signal Streams and programmed I/O, use the Data Transfer Mechanism property node function in NI-DAQmx. NI USB-621x User Manual section of Chapter 7, Analog Output, for more information.

  • Page 133: Triggering

    Analog Input Digital Triggering Input Analog Output Digital Triggering Output Counter Triggering section of Chapter 9, Digital Trigger Falling Edge Initiates Acquisition Figure 14-1. Falling-Edge Trigger 14-1 section of Chapter 4, Analog section of Chapter 7, Analog Counters NI USB-621x User Manual...
  • Page 134 You also can program your DAQ device to perform an action in response to a trigger from a digital source. The action can affect the following: • • • NI USB-621x User Manual Analog input acquisition Analog output generation Counter behavior 14-2...

  • Page 135: Device-Specific Information

    Figure A-1 shows the pinout of the NI 6210. For a detailed description of each signal, refer to the Descriptions © National Instruments Corporation USB-6210 USB-6211/6215 USB 6218 section of Chapter 3, Connector ni.com/ I/O Connector Signal Information. NI USB-621x User Manual...
  • Page 136 Appendix A Device-Specific Information NI USB-621x User Manual PFI 0/P0.0 (In) PFI 1/P0.1 (In) PFI 2/P0.2 (In) PFI 3/P0.3 (In) D GND PFI 4/P1.0 (Out) PFI 5/P1.1 (Out) PFI 6/P1.2 (Out) PFI 7/P1.3 (Out) +5 V D GND RESERVED AI 0...
  • Page 137 Default Terminal Number (Name) 2 (PFI 1) 1 (PFI 0) 4 (PFI 3) 3 (PFI 2) 4 (PFI 3) 7 (PFI 5) 4 (PFI 3) 3 (PFI 2) 4 (PFI 3) 8 (PFI 6) Device Status ni.com/support NI USB-621x User Manual...

  • Page 138: Usb-6211/6215

    USB-6211/6215 USB-6211/6215 Pinout Figure A-2 shows the pinout of the NI 6211/6215. For a detailed description of each signal, refer to the Descriptions NI USB-621x User Manual Table A-2. PWR/ACT LED Status (Continued) LED State Single-blink Operating normally. Connected to USB Hi-Speed port.
  • Page 139 CTR 0 AUX CTR 0 OUT CTR 0 A CTR 0 Z Appendix A Device-Specific Information Default Terminal Number (Name) 1 (PFI 0) 2 (PFI 1) 1 (PFI 0) 6 (PFI 4) 1 (PFI 0) 2 (PFI 1) NI USB-621x User Manual...
  • Page 140 Refer to the NI 621x Specifications for more detailed information about the USB-6211/6215 device. USB-6211/6215 PWR/ACT LED Indicator The PWR/ACT LED indicator indicates device status. NI USB-621x User Manual Table A-3. Default NI-DAQmx Counter/Timer Pins (Continued) Counter/Timer Signal CTR 0 B...

  • Page 141: Usb 6218

    NI 621x Specifications for more information. Double-blink Connected to USB full speed port. Device performance might be affected. Refer to the NI 621x Specifications for more information. section of Chapter 3, Connector Device-Specific Information Device Status I/O Connector Signal Information. NI USB-621x User Manual...
  • Page 142 Appendix A Device-Specific Information NI USB-621x User Manual PFI 0/P0.0 (In) PFI 1/P0.1 (In) PFI 2/P0.2 (In) PFI 3/P0.3 (In) D GND PFI 4/P1.0 (Out) PFI 5/P1.1 (Out) PFI 6/P1.2 (Out) PFI 7/P1.3 (Out) +5 V D GND AO 0...
  • Page 143 Device-Specific Information Default Terminal Number (Name) 34 (PFI 9) 4 (PFI 3) 3 (PFI 2) 35 (PFI 10) 7 (PFI 5) 4 (PFI 3) 3 (PFI 2) 35 (PFI 10) 8 (PFI 6) Device Status ni.com/support NI USB-621x User Manual...
  • Page 144 Appendix A Device-Specific Information NI USB-621x User Manual Table A-6. PWR/ACT LED Status (Continued) LED State Single-blink Operating normally. Connected to USB Hi-Speed port. Refer to the NI 621x Specifications for more information. Double-blink Connected to USB full speed port.

  • Page 145: Troubleshooting

    Troubleshooting This section contains common questions about M Series devices. If your questions are not answered here, refer to the National Instruments KnowledgeBase at Analog Input I am seeing crosstalk or ghost voltages when sampling multiple channels. What does this mean?
  • Page 146 This method allows multiple channels to be sampled relatively quickly in relationship to the overall sample rate, providing a nearly simultaneous effect with a fixed delay between channels. NI USB-621x User Manual Connecting AI Signals on the USB-6210/6211 Devices Connecting AI Signals on the USB-6215/6218...

  • Page 147: Analog Output

    You can build a lowpass deglitching filter to remove some of these glitches, depending on the frequency and nature of the output signal. Visit ni.com/support © National Instruments Corporation Appendix B for more information about minimizing glitches. Troubleshooting NI USB-621x User Manual...

  • Page 148: Technical Support And Professional Services

    Technical Support and Professional Services Visit the following sections of the National Instruments Web site at ni.com • • • • © National Instruments Corporation for technical support and professional services: Support—Online technical support resources at include the following: –...
  • Page 149 Worldwide Offices section of office Web sites, which provide up-to-date contact information, support phone numbers, email addresses, and current events. NI USB-621x User Manual Calibration Certificate—If your product supports calibration, you can obtain the calibration certificate for your product at...
  • Page 150 A measure of the capability of an instrument or sensor to faithfully indicate the value of the measured signal. This term is not related to resolution; however, the accuracy level can never be better than the resolution of the instrument. Application development environment. © National Instruments Corporation NI USB-621x User Manual...
  • Page 151 The process of getting an instrument ready to perform a function. For example, the trigger circuitry of a digitizer is armed, meaning that it is ready to start acquiring data when an appropriate trigger condition is met. NI USB-621x User Manual ni.com...
  • Page 152 When that relationship is known, the instrument may then be adjusted (calibrated) for best accuracy. calibrator A precise, traceable signal source used to calibrate instruments. © National Instruments Corporation Glossary NI USB-621x User Manual...
  • Page 153 The number of events, such as zero crossings, pulses, or cycles. counter 1. Software. A memory location used to store a count of certain occurrences. 2. Hardware. A circuit that counts events. When it refers to an instrument, it refers to a frequency counter. NI USB-621x User Manual ni.com...
  • Page 154 Data acquisition system timing controller chip. data acquisition The general concept of acquiring data, as in begin data acquisition or data acquisition and control. See also DAQ. © National Instruments Corporation ® ) port. SCXI modules are considered DAQ devices. Glossary NI USB-621x User Manual...
  • Page 155 Dynamic digital I/O refers to digital systems where the signals are continuously changing, often at multi-MHz clock rates. digital signal A representation of information by a set of discrete values according to a prescribed law. These values are represented by numbers. NI USB-621x User Manual ni.com...
  • Page 156 EXTCLK External clock signal. external trigger A voltage pulse from an external source that causes a DAQ operation to begin. EXTREF External reference signal. © National Instruments Corporation Glossary NI USB-621x User Manual...
  • Page 157 Also called non-referenced signal sources. Some common examples of floating signal sources are batteries, transformers, and thermocouples. FREQ OUT Frequency Output signal. frequency The number of alternating signals that occur per unit time. Feet. NI USB-621x User Manual ni.com...
  • Page 158 Lag between making a change and the effect of the change. Input/Output—The transfer of data to/from a computer system involving communications channels, operator interface devices, and/or data acquisition and control interfaces. © National Instruments Corporation Glossary NI USB-621x User Manual...
  • Page 159 2. A computer signal indicating that the CPU should suspend its current task to service a designated activity. Current, output high. Current, output low. See interrupt, interrupt request line. Kilohertz—A unit of frequency; 1 kHz = 10 1,000 samples. NI USB-621x User Manual = 1,000 Hz. G-10 ni.com...
  • Page 160 A board assembly and its associated mechanical parts, front panel, optional shields, and so on. A module contains everything required to occupy one or more slots in a mainframe. SCXI and PXI devices are modules. © National Instruments Corporation Hz = 1,000,000 Hz. –6 G-11 Glossary NI USB-621x User Manual...
  • Page 161 National Instruments. NI-DAQ The driver software needed to use National Instruments DAQ devices and SCXI components. Some devices use Traditional NI-DAQ (Legacy); others use NI-DAQmx. NI-DAQmx The latest NI-DAQ driver with new VIs, functions, and development tools for controlling measurement devices.
  • Page 162 (in Hz). Period is designated by the symbol T. periods The number of periods of a signal. Programmable Function Interface. PGIA Programmable Gain Instrumentation Amplifier. physical channel See channel. © National Instruments Corporation G-13 Glossary NI USB-621x User Manual...
  • Page 163 The time from the rising to the falling slope of a pulse (at 50% amplitude). A rugged, open system for modular instrumentation based on CompactPCI, with special mechanical, electrical, and software features. The PXIbus standard was originally developed by National Instruments in 1997, and is now managed by the PXIbus Systems Alliance. PXI Express PCI Express eXtensions for Instrumentation—The PXI implementation of...
  • Page 164 RTSI Real-Time System Integration. RTSI bus Real-Time System Integration bus—The National Instruments timing bus that connects DAQ devices directly, by means of connectors on top of the devices, for precise synchronization of functions. Seconds. Samples.
  • Page 165 Describes a device that acquires a specified number of samples from one or more channels and returns the data when the acquisition is complete. single-ended input A circuit that responds to the voltage on one input terminal and ground. See also NI USB-621x User Manual differential input. G-16 ni.com...
  • Page 166 See terminal count. terminal An object or region on a node through which data passes. terminal count The highest value of a counter. Gate hold time. Gate setup time. Gate pulse width. © National Instruments Corporation G-17 Glossary NI USB-621x User Manual...
  • Page 167 Universal Serial Bus—A 480 Mbit/s serial bus with up to 12-Mbps bandwidth for connecting computers to keyboards, printers, and other peripheral devices. USB 2.0 retains compatibility with the original USB specification. Volts. Common-mode voltage. NI USB-621x User Manual G-18 ni.com...
  • Page 168 See channel. waveform 1. The plot of the instantaneous amplitude of a signal as a function of time. 2. Multiple voltage readings taken at a specific sampling rate. © National Instruments Corporation G-19 Glossary NI USB-621x User Manual...
  • Page 169 B-1 analog input data acquisitions, 4-9 analog input signals, 4-11 AI Convert Clock, 4-16 AI Convert Clock Timebase, 4-20 AI Hold Complete Event, 4-21 AI Pause Trigger, 4-23 AI Reference Trigger, 4-22 AI Sample Clock, 4-14 NI USB-621x User Manual...
  • Page 170 9-2 counter output, 9-20 edge counting, 9-2 arm start trigger, 9-31 avoiding scanning faster than necessary, 4-8 NI USB-621x User Manual buffered edge counting, 9-3 non-cumulative, 9-4 buffered hardware-timed acquisitions, 4-10 buffered hardware-timed generations, 7-3 buffered period measurement, 9-7...
  • Page 171 B-1 DACs, 7-1 DAQ hardware, 2-1 DAQ system, 2-1 DAQ-STC2, 2-2 data acquisition methods, 4-9 generation methods, 7-2 transfer methods, 13-1 changing, 13-2 programmed I/O, 13-2 USB signal stream, 13-1 Index NI USB-621x User Manual...
  • Page 172 I/O, 8-1 block diagram, 8-1 circuitry, 8-1 connecting signals, 8-3 getting started with applications in software, 8-4 I/O protection, 8-2 NI USB-621x User Manual static DIO, 8-2 triggering, 14-1 digital routing, 12-1 digital signals connecting, 8-3 digital source, triggering, 14-1...
  • Page 173 USB-6218 pinout, A-7 I/O protection, 8-2, 10-6 input signals using PFI terminals as, 10-2 insertion of grounded channels between signal channels, 4-7 installation hardware, 1-3 NI-DAQ, 1-2 other software, 1-2 instrument drivers (NI resources), C-1 Index NI USB-621x User Manual...
  • Page 174 9-10 period, 9-6 position, 9-15 pulse-width, 9-5 semi-period, 9-9 single period, 9-7 single pulse-width, 9-5 NI USB-621x User Manual single semi-period, 9-9 single two-signal edge-separation, 9-18 two-signal edge-separation, 9-18 using quadrature encoders, 9-15 using two pulse encoders, 9-17 measuring...
  • Page 175 9-22 continuous, 9-22 pulse-width measurement, 9-5 buffered, 9-5 single, 9-5 quadrature encoders, 9-15 reciprocal frequency measurement, 9-12 referenced single-ended connections using with floating signal sources, 5-9 when to use with floating signal sources, 5-3 Index NI USB-621x User Manual...
  • Page 176 AI Reference Trigger, 4-22 AI Sample Clock, 4-14 AI Sample Clock Timebase, 4-16 AI Start Trigger, 4-21 analog input, 4-11 NI USB-621x User Manual analog output, 7-5 AO Pause Trigger, 7-6 AO Sample Clock, 7-7 AO Sample Clock Timebase, 7-8...
  • Page 177 USB-6210, A-1 analog input signals, 5-1 LED, A-3 pinout, A-1 specifications, A-3 USB-6211, A-4 analog input signals, 5-1 LED, A-6 pinout, A-4 specifications, A-6 USB-6215, A-4 analog input signals, 6-1 LED, A-6 pinout, A-4 specifications, A-6 Index NI USB-621x User Manual...
  • Page 178 4-6 using PFI terminals as static digital I/Os, 10-3 as timing input signals, 10-2 to export timing output signals, 10-3 NI USB-621x User Manual waveform generation signals, 7-5 Web resources, C-1 X1 encoding, 9-15 X2 encoding, 9-16...

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