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National Instruments NI 6238 User Manual

National Instruments NI 6238 User Manual

Daq m series isolated current input/c urrent output devices
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DAQ M Series
NI 6238/6239 User Manual
Isolated Current Input/Current Output Devices
NI 6238/6239 User Manual
July 2006
371913A-01

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  • Page 1 DAQ M Series NI 6238/6239 User Manual Isolated Current Input/Current Output Devices NI 6238/6239 User Manual July 2006 371913A-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

    Warranty The NI 6238/6239 is warranted against defects in materials and workmanship for a period of three years from the date of shipment, as evidenced by receipts or other documentation. National Instruments will, at its option, repair or replace equipment that proves to be defective during the warranty period.
  • 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

    DAQ Hardware ...2-1 DAQ-STC2...2-2 Calibration Circuitry...2-3 Sensors and Transducers...2-3 Cables and Accessories...2-4 Custom Cabling ...2-4 Programming Devices in Software ...2-5 Chapter 3 Connector Information I/O Connector Signal Descriptions ...3-1 RTSI Connector Pinout...3-3 © National Instruments Corporation NI 6238/6239 User Manual...
  • Page 6 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 NI 6238/6239 User Manual ni.com...
  • Page 7 Getting Started with AO Applications in Software ...5-10 Chapter 6 Digital Input and Output I/O Protection...6-1 Programmable Power-Up States ...6-1 Connecting Digital I/O Signals...6-2 Logic Conventions ...6-3 Getting Started with DIO Applications in Software ...6-4 © National Instruments Corporation Contents NI 6238/6239 User Manual...
  • Page 8 Retriggerable Single Pulse Generation... 7-22 Pulse Train Generation... 7-23 Continuous Pulse Train Generation... 7-23 Frequency Generation ... 7-24 Using the Frequency Generator ... 7-24 Frequency Division ... 7-25 Pulse Generation for ETS ... 7-25 NI 6238/6239 User Manual viii ni.com...
  • Page 9 Example Application That Prevents Duplicate Count ...7-37 When To Use Duplicate Count Prevention...7-38 Enabling Duplicate Count Prevention in NI-DAQmx ...7-38 Synchronization Modes ...7-38 80 MHz Source Mode ...7-39 Other Internal Source Mode...7-39 External Source Mode...7-40 © National Instruments Corporation Contents NI 6238/6239 User Manual...
  • Page 10 Using RTSI as Outputs ... 10-5 Using RTSI Terminals as Timing Input Signals ... 10-6 RTSI Filters... 10-6 PXI Clock and Trigger Signals... 10-7 PXI_CLK10 ... 10-8 PXI Triggers... 10-8 PXI_STAR Trigger ... 10-8 PXI_STAR Filters... 10-8 NI 6238/6239 User Manual ni.com...
  • Page 11 Appendix B Troubleshooting Analog Input ...B-1 Analog Output...B-2 Counters ...B-3 Appendix C Technical Support and Professional Services Glossary Index Figures Figure A-1. NI 6238 Pinout ...A-2 Figure A-2. NI 6239 Pinout ...A-5 © National Instruments Corporation Contents NI 6238/6239 User Manual...

  • Page 12: About This Manual

    About This Manual The NI 6238/6239 User Manual contains information about using the NI 6238 and NI 6239 M Series data acquisition (DAQ) devices with NI-DAQmx 8.1 and later. National Instruments 6238/6239 devices feature up to eight differential analog input (AI) channels, two analog output (AO) channels, two counters, six lines of digital input (DI), and four lines of digital output (DO).

  • Page 13: Related Documentation

    Programs»National Instruments»NI-DAQ»DAQ Getting Started Guide. The NI-DAQ Readme lists which devices are supported by this version of NI-DAQ. Select Start»All Programs»National Instruments»NI-DAQ» NI-DAQ Readme. The NI-DAQmx Help contains general information about measurement concepts, key NI-DAQmx concepts, and common applications that are applicable to all programming environments.

  • Page 14: Ni-Daqmx Base

    Use the LabVIEW Help, available by selecting Help»Search the LabVIEW Help in LabVIEW, to access information about LabVIEW programming concepts, step-by-step instructions for using LabVIEW, and reference information about LabVIEW VIs, functions, palettes, menus, and © National Instruments Corporation and opening About This Manual NI 6238/6239 User Manual...

  • Page 15: Labwindows™/Cvi

    The NI-DAQmx Help contains API overviews and general information about measurement concepts. Select Start»All Programs»National Instruments»NI-DAQmx Help. NI 6238/6239 User Manual Getting Started»Getting Started with DAQ—Includes overview information and a tutorial to learn how to take an NI-DAQmx measurement in LabVIEW using the DAQ Assistant.

  • Page 16: Net Languages Without Ni Application Software

    Note You must have Visual Studio .NET installed to view the NI Measurement Studio Help. Device Documentation and Specifications The NI 6238/6239 Specifications contains all specifications for NI 6238 and NI 6239 M Series devices. NI-DAQ 7.0 and later includes the Device Document Browser, which...

  • Page 17: Getting Started

    (DI), and four lines of digital output (DO). If you have not already installed your device, refer to the DAQ Getting Started Guide. For NI 6238 and NI 6239 device specifications, refer to the NI 6238/6239 Specifications on Before installing your DAQ device, you must install the software you plan to use with the device.

  • Page 18: Device Specifications

    Chapter 1 Getting Started Device Specifications Refer to the NI 6238/6239 Specifications, available on the NI-DAQ Device Document Browser or on NI 6238/6239 devices. Device Accessories and Cables NI offers a variety of accessories and cables to use with your DAQ device.

  • Page 19: Daq System Overview

    Accessories DAQ Hardware DAQ hardware digitizes input signals, performs D/A conversions to generate analog output signals, and measures and controls digital I/O signals. Figure 2-2 features the components of the NI 6238/6239 devices. © National Instruments Corporation Hardware Software Figure 2-1. Components of a Typical DAQ System...

  • Page 20: Daq-Stc2

    DAQ System Overview Analog Input Analog Output Counters PFI/Static DI PFI/Static DO DAQ-STC2 The DAQ-STC2 implements a high-performance digital engine for NI 6238/6239 data acquisition hardware. Some key features of this engine include the following: • • • • • •...

  • Page 21: Calibration Circuitry

    Taking Measurements book on the Contents tab. If you are using other application software, refer to Common Sensors in the NI-DAQmx Help, which can be accessed from Start»All Programs»National Instruments»NI-DAQ»NI-DAQmx Help. Chapter 2 DAQ System Overview ni.com/sensors NI 6238/6239 User Manual...

  • Page 22: Cables And Accessories

    Chapter 2 DAQ System Overview Cables and Accessories NI offers a variety of products to use with NI 6238/6239 devices, including cables, connector blocks, and other accessories, as follows: • • • For more specific information about these products, refer to...

  • Page 23: Programming Devices In Software

    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

    Output Analog Output Channels 0 to 1—These terminals supply the current output of AO channels 0 to 1. Note: AO <0..1> are isolated from earth ground and chassis ground. RTSI Connector Pinout Description Analog Input. NI 6238/6239 User Manual...
  • Page 25 P1.GND — P1.VCC — AO POWER SUPPLY — NI 6238/6239 User Manual Table 3-1. I/O Connector Signals (Continued) Direction — Analog Output Ground—AO GND is the reference for AO <0..1>. AI GND and AO GND are connected on the device.

  • Page 26: Rtsi Connector Pinout

    External Calibration Negative Reference—CAL– supplies the negative reference during external calibration of the NI 6238/6239. RTSI Connector Pinout Generation, for information on the RTSI connector. Chapter 3 Connector Information Description section of Chapter 10, Digital Routing NI 6238/6239 User Manual...

  • Page 27: Analog Input

    Analog Input Figure 4-1 shows the analog input circuitry of NI 6238 and NI 6239 devices. AI <0..7>+ AI Terminal Configuration AI <0..7>– Selection AI GND Analog Input Circuitry I/O Connector You can connect analog input signals to the M Series device through the I/O connector.

  • Page 28: Analog Input Range

    So, for an input range of ±20 mA, the current of each code of a 16-bit ADC is: NI 6238/6239 User Manual ) codes—that is, one of 65,536 possible digital values. These...

  • Page 29: Connecting Analog Current Input Signals

    For more information on programming these settings, refer to the NI-DAQmx Help or the LabVIEW 8.x Help. Table 4-1 shows the input ranges and resolutions supported by the NI 6238 and NI 6239 devices. Connecting Analog Current Input Signals When making signal connections, caution must be taken with the voltage level of the signal going into the device.

  • Page 30: Method 2

    Method 2, shown in Figure 4-3, ties the AI – input to AI GND. When measuring current up to 20 mA, this type of connection ensures that the voltage level on both the positive and negative side are within the common-mode input range for NI 6238/6239 devices. AI + AI –...

  • Page 31: Analog Input Ground-Reference Settings

    Note that AI GND must always be connected to some voltage level. AI GND is the reference that NI 6238/6239 devices measure against. The NI 6238 and NI 6239 are isolated devices with isolation ratings up to 60 VDC/30 Vrms. This allows for current measurement at high voltage levels provided that the common-mode input range requirement is satisfied.
  • Page 32 NI 6238/6239 User Manual Current Sense PGIA Resistor in– AI GND Figure 4-5. NI 6238/6239 PGIA Connecting Analog Current Input Signals Table 4-2. Signals Routed to the NI-PGIA Signals Routed to the Positive Input of the NI-PGIA (V AI <0..7>+ Internal Channels...

  • Page 33: Configuring Ai Ground-Reference Settings In Software

    Caution The maximum input voltages rating of AI signals with respect to AI GND (and for differential signals with respect to each other) and earth/chassis ground are listed in the Maximum Working Voltage section of the NI 6238/6239 Specifications. Exceeding the maximum input voltage or maximum working voltage of AI signals distorts the measurement results.

  • Page 34: Multichannel Scanning Considerations

    Settling time refers to the time it takes the NI-PGIA to amplify the input signal to the desired accuracy before it is sampled by the ADC. The NI 6238/6239 Specifications shows the device settling time. M Series devices are designed to have fast settling times. However, several factors can increase the settling time which decreases the accuracy of your measurements.

  • Page 35: Avoid Scanning Faster Than Necessary

    1, and so on. You also could read all 100 points from channel 0 then read 100 points from channel 1. The second method switches between channels much less often and is affected much less by settling time. © National Instruments Corporation Chapter 4 Analog Input NI 6238/6239 User Manual...

  • Page 36: Analog Input Data Acquisition Methods

    Finite sample mode acquisition refers to the acquisition of a specific, predetermined number of data samples. After the specified number of NI 6238/6239 User Manual The time between samples can be much shorter. The timing between samples is deterministic.

  • Page 37: Non-Buffered

    • • Refer to the Pause Trigger Signal A digital trigger can initiate these actions. NI 6238/6239 devices support digital triggering, but do not support analog triggering. Field Wiring Considerations Environmental noise can seriously affect the measurement accuracy of the device if you do not take proper care when running signal wires between signal sources and the device.

  • Page 38: Analog Input Timing Signals

    Analog Input Timing Signals In order to provide all of the timing functionality described throughout this section, NI 6238/6239 devices have a flexible timing engine. Figure 4-7 summarizes all of the timing options provided by the analog input timing engine. Also refer to the...
  • Page 39 10 μs, 4 μs (1/250000) + 10 μs, which results in 14 μs or 71428.6 Hz. © National Instruments Corporation Channel 0 Channel 1 Convert Period Sample Period Figure 4-8. Interval Sampling 4-13 Chapter 4 Analog Input NI 6238/6239 User Manual...
  • Page 40 When the ai/StartTrigger pulse occurs, the sample counter is loaded with the number of pretriggered samples, in this NI 6238/6239 User Manual ai/StartTrigger Figure 4-9. Posttriggered Data Acquisition Example 4-14 ni.com...

  • Page 41: Ai Sample Clock Signal

    Otherwise, when the ai/ReferenceTrigger pulse occurs, the sample counter value decrements until the specified number of posttrigger samples have been acquired. NI 6238/6239 devices feature the following analog input timing signals. • • •...

  • Page 42: Using An Internal Source

    Use one of the following external signals as the source of ai/SampleClock: • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. Routing AI Sample Clock Signal to an Output Terminal You can route ai/SampleClock out to any output PFI <6..9>...

  • Page 43: Other Timing Requirements

    © National Instruments Corporation AI Convert Clock Signal section for more information on the timing ai/SampleClockTimebase ai/StartTrigger ai/SampleClock Figure 4-11. ai/SampleClock and ai/StartTrigger 20 MHz Timebase 100 kHz Timebase PXI_CLK10 4-17 Chapter 4 Analog Input Delay From Start Trigger NI 6238/6239 User Manual...

  • Page 44: Ai Convert Clock Signal

    Timebase to generate ai/ConvertClock. The counter is started by ai/SampleClock and continues to count down to zero, produces an ai/ConvertClock, reloads itself, and repeats the process until the sample is NI 6238/6239 User Manual RTSI <0..7> Input PFI <0..5> PXI_STAR...

  • Page 45: Using An External Source

    Use one of the following external signals as the source of ai/ConvertClock: • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. Routing AI Convert Clock Signal to an Output Terminal You can route ai/ConvertClock (as an active low signal) out to any output PFI <6..9>...

  • Page 46: Other Timing Requirements

    It is also possible to use a single external signal to drive both ai/SampleClock and ai/ConvertClock at the same time. In this mode, each tick of the external clock will cause a conversion on the ADC. Figure 4-13 shows this timing relationship. NI 6238/6239 User Manual Delay Convert From...

  • Page 47: Ai Convert Clock Timebase Signal

    © National Instruments Corporation ai/SampleClock ai/ConvertClock Channel Measured Sample #1 Sample #2 Sample #3 • One External Signal Driving Both Clocks Simultaneously ai/SampleClockTimebase 20 MHz Timebase 4-21 Chapter 4 Analog Input 1 2 3 1 … 1 2 3 NI 6238/6239 User Manual...

  • Page 48: Ai Start Trigger Signal

    • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. 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.

  • Page 49: Ai Reference Trigger Signal

    Figure 4-14 shows the final buffer. © National Instruments Corporation and enter the info code Reference Trigger Pretrigger Samples Complete Buffer Figure 4-14. Reference Trigger Final Buffer 4-23 Chapter 4 Analog Input rdcanq Posttrigger Samples NI 6238/6239 User Manual...

  • Page 50: Using A Digital Source

    • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. 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.

  • Page 51: Routing Ai Pause Trigger Signal To An Output Terminal

    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. © National Instruments Corporation Single-point analog input Finite analog input Continuous analog input 4-25 Chapter 4 Analog Input NI 6238/6239 User Manual...

  • Page 52: Analog Output

    Analog Output NI 6238/6239 devices have two AO channels controlled by a single clock and capable of waveform generation. Figure 5-1 shows the analog current output circuitry of NI 6238 and NI 6239 devices. AO POWER SUPPLY AO 0 AO 1...

  • Page 53: Analog Output Data Generation Methods

    • Hardware-timed operations can be buffered or non-buffered. A buffer is a temporary storage in computer memory for to-be-generated samples. NI 6238/6239 User Manual The time between samples can be much shorter. The timing between samples can be deterministic. Hardware-timed acquisitions can use hardware triggering.

  • Page 54: Non-Buffered

    With non-regeneration, old data will not be repeated. New data must be continually written to the buffer. If the program does not write new data to © National Instruments Corporation NI 6238/6239 User Manual...

  • Page 55: Analog Output Triggering

    Figure 5-2 shows how to make analog current output connections to the device. Tip Internal voltage drop for the NI 6238/6239 devices is a maximum of 3 V relative to the externally supplied voltage. Caution The maximum output voltages rating of AO signals and input voltage ratings for...

  • Page 56: Analog Output Timing Signals

    Maximum Working Voltage section of the NI 6238/6239 Specifications. Exceeding the maximum input supply voltage or maximum working voltage of AO signals distorts the measurement results. Exceeding the maximum input supply voltage or maximum working voltage rating also can damage the device and the computer. Exceeding the maximum output voltage can cause injury and harm the user.

  • Page 57: Using A Digital Source

    • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. The source also can be one of several 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.

  • Page 58: Using A Digital Source

    • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. 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.

  • Page 59: Routing Ao Pause Trigger Signal To An Output Terminal

    Use one of the following external signals as the source of ao/SampleClock: • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. Routing AO Sample Clock Signal to an Output Terminal You can route ao/SampleClock (as an active low signal) out to any output PFI <6..9>...

  • Page 60: Other Timing Requirements

    Timebase (ao/SampleClockTimebase) signal: • • • • • • Note Refer to the NI 6238/6239 Specifications for the minimum allowable pulse width and the propagation delay of PFI <0..5>. © National Instruments Corporation ao/SampleClockTimebase ao/StartTrigger ao/SampleClock Figure 5-6. ao/SampleClock and ao/StartTrigger...

  • Page 61: Getting Started With Ao Applications In Software

    DMA data transfer mechanisms. Some of the applications also use start triggers and pause triggers. 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. NI 6238/6239 User Manual Single-point (on-demand) generation Finite generation Continuous generation...

  • Page 62: Digital Input And Output

    P1.<0..3>. These lines also can be used as PFI output. The voltage input and output levels and the current drive level of the DI and DO lines are listed in the NI 6238/6239 Specifications. Refer to Chapter 8, PFI, for more information on PFI inputs and outputs.

  • Page 63: Connecting Digital I/O Signals

    The DI signals P0.<0..5> are referenced to P0.GND and DO signals P1.<0..3> are referenced to P1.GND. Figures 6-1 and 6-2 show P0.<0..5> and P1.<0..3> on the NI 6238 and the NI 6239 device, respectively. Digital input and output signals can range from 0 to 30 V.

  • Page 64: Logic Conventions

    P0.GND Caution Exceeding the maximum input voltage or maximum working voltage ratings, which are listed in the NI 6238/6239 Specifications, can damage the DAQ device and the computer. NI is not liable for any damage resulting from such signal connections.

  • Page 65: Getting Started With Dio Applications In Software

    Digital Input and Output NI 6238 (Source) NI 6239 (Sink) Getting Started with DIO Applications in Software You can use NI 6238/6239 devices in the following digital I/O applications: • • 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.
  • Page 66 Caution When making measurements, take into account the minimum pulse width and time delay of the digital input and output lines. Refer to the NI 6238/6239 Specifications for more information. © National Instruments Corporation...
  • Page 67 The counters have seven input signals, although in most applications only a few inputs are used. For information on connecting counter signals, refer to the Terminals NI 6238/6239 User Manual Counter 0 Counter 0 Source (Counter 0 Timebase) Counter 0 Gate...

  • Page 68: Counters

    Figure 7-3 shows an example of on-demand edge counting with a pause trigger. © National Instruments Corporation Counter Armed SOURCE Counter Value Figure 7-2. Single Point (On-Demand) Edge Counting Chapter 7 Counters NI 6238/6239 User Manual...

  • Page 69: Buffered (Sample Clock) Edge Counting

    Figure 7-4 shows an example of buffered edge counting. Notice that counting begins when the counter is armed, which occurs before the first active edge on Gate. NI 6238/6239 User Manual Counter Armed Pause Trigger (Pause When Low)

  • Page 70: Non-Cumulative Buffered Edge Counting

    Counter Armed Buffer Figure 7-5. Non-Cumulative Buffered Edge Counting Always count up Always count down Count up when the Counter n B input is high; count down when it is section. Chapter 7 Counters Default Counter NI 6238/6239 User Manual...

  • Page 71: Pulse-Width Measurement

    Figure 7-6 shows an example of a single pulse-width measurement. HW Save Register 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. NI 6238/6239 User Manual GATE SOURCE Counter Value Figure 7-6. Single Pulse-Width Measurement ni.com...

  • Page 72: Period Measurement

    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. © National Instruments Corporation Figure 7-7. Buffered Pulse-Width Measurement section. Chapter 7 Counters Default Counter NI 6238/6239 User Manual...

  • Page 73: Single Period Measurement

    Gate input. So the first value stored in the hardware save register does not reflect a full period of the Gate input. In most applications, this first point should be discarded. Figure 7-9 shows an example of a buffered period measurement. NI 6238/6239 User Manual GATE SOURCE Counter Value Figure 7-8.

  • Page 74: Semi-Period Measurement

    Source signal by the number of edges returned by the counter. Single Semi-Period Measurement Single semi-period measurement is equivalent to single pulse-width measurement. © National Instruments Corporation (Discard) Figure 7-9. Buffered Period Measurement section. Chapter 7 Counters (Discard) (Discard) Default Counter NI 6238/6239 User Manual...

  • Page 75: Buffered Semi-Period Measurement

    Method 1—Measure Low Frequency with One Counter In this method, you measure one period of your signal using a known timebase. This method is good for low frequency signals. NI 6238/6239 User Manual Counter Armed GATE SOURCE Counter Value Buffer Figure 7-10.

  • Page 76: Method 1B-Measure Low Frequency With One Counter (Averaged)

    F1. The frequency of F1 is the inverse of the average period. Figure 7-12 illustrates this method. © National Instruments Corporation Interval Measured … Period of F1 = Frequency of F1 = Figure 7-11. Method 1 7-11 Chapter 7 Counters … NI 6238/6239 User Manual...

  • Page 77: Method 2-Measure High Frequency With Two Counters

    T to be N periods of F1. Then the frequency of F1 is N/T. Figure 7-13 illustrates this method. Another option would be to measure the width of a known period instead of a known pulse. NI 6238/6239 User Manual Gate 1 2 ... N...

  • Page 78: Method 3-Measure Large Range Of Frequencies Using Two Counters

    Configure Counter 0 to generate a single pulse that is the width of N periods of the source input signal. © National Instruments Corporation Width of Pulse (T) Pulse … Width of Pulse Frequency of F1 = Figure 7-13. Method 2 7-13 Chapter 7 Counters NI 6238/6239 User Manual...

  • Page 79: Choosing A Method For Measuring Frequency

    The best method to measure frequency depends on several factors including the expected frequency of the signal to measure, the desired accuracy, how many counters are available, and how long the measurement can take. • NI 6238/6239 User Manual Signal to SOURCE Measure (F1)
  • Page 80 Method 3 measures high and low frequency signals accurately. However, it requires two counters. 7-15 Chapter 7 Counters Example 1 Example 2 50 kHz 5 MHz 80 MHz 80 MHz 1600 1599 50.125 kHz 5.33 MHz 125 kHz 333 kHz 0.06% 6.67% NI 6238/6239 User Manual...

  • Page 81: Position Measurement

    X1 encoding. When channel A leads channel B, the increment occurs on the rising edge of channel A. When channel B leads channel A, the decrement occurs on the falling edge of channel A. NI 6238/6239 User Manual Measures High Number of...

  • Page 82: Channel Z Behavior

    © National Instruments Corporation Ch A Ch B Counter Value Figure 7-15. X1 Encoding Ch A Ch B Counter Value 5 Figure 7-16. X2 Encoding Figure 7-17. X4 Encoding 7-17 Chapter 7 NI 6238/6239 User Manual Counters...

  • Page 83: Measurements Using Two Pulse Encoders

    A and B. The counter increments on each rising edge of channel A. The counter decrements on each rising edge of channel B, as shown in Figure 7-19. Counter Value 2 NI 6238/6239 User Manual Ch A Ch B Ch Z...

  • Page 84: Two-Signal Edge-Separation Measurement

    The counter then stores the count in a hardware save register and ignores other edges on its inputs. Software then can read the stored count. Figure 7-20 shows an example of a single two-signal edge-separation measurement. © National Instruments Corporation section. 7-19 Chapter 7 Counters Default Counter NI 6238/6239 User Manual...

  • Page 85: Buffered Two-Signal Edge-Separation Measurement

    A DMA controller transfers the stored values to host memory. Figure 7-21 shows an example of a buffered two-signal edge-separation measurement. For information on connecting counter signals, refer to the Terminals NI 6238/6239 User Manual Counter Armed GATE SOURCE Counter Value Figure 7-20.

  • Page 86: Counter Output Applications

    Figure 7-23 shows a generation of a pulse with a pulse delay of four and a pulse width of three (using the rising edge of Source). © National Instruments Corporation Counter Armed SOURCE Figure 7-22. Single Pulse Generation 7-21 Chapter 7 Counters NI 6238/6239 User Manual...

  • Page 87: Retriggerable Single Pulse Generation

    Figure 7-24 shows a generation of two pulses with a pulse delay of five and a pulse width of three (using the rising edge of Source). For information on connecting counter signals, refer to the Terminals NI 6238/6239 User Manual GATE (Start Trigger) SOURCE Figure 7-23.

  • Page 88: Pulse Train Generation

    Source input divided by M + N. For information on connecting counter signals, refer to the Terminals © National Instruments Corporation SOURCE Counter Armed Figure 7-25. Continuous Pulse Train Generation section. 7-23 Chapter 7 Counters Default Counter NI 6238/6239 User Manual...

  • Page 89: Frequency Generation

    Figure 7-27 shows the output waveform of the frequency generator when the divider is set to 5. Frequency Output Timebase Freq Out (Divisor = 5) NI 6238/6239 User Manual Frequency Output Timebase Figure 7-26. Frequency Generator Block Diagram Figure 7-27. Frequency Generator Output Waveform 7-24...

  • Page 90: 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 © National Instruments Corporation section. section. 7-25 Chapter 7 Counters Default Counter Default Counter NI 6238/6239 User Manual...

  • Page 91: Counter Timing Signals

    Counter n Source Signal The selected edge of the Counter n Source signal increments and decrements the counter value depending on the application the counter is NI 6238/6239 User Manual GATE D2 = D1 + ΔD Figure 7-28. Pulse Generation for ETS section.

  • Page 92: Routing A Signal To Counter N Source

    80 MHz Timebase 20 MHz Timebase 100 kHz Timebase RTSI <0..7> Input PFI <0..5> PXI_CLK10 PXI_STAR 7-27 Chapter 7 Counters Purpose of Source Terminal Counter Timebase Counter Timebase Input Terminal Input Terminal Input Terminal Counter Timebase NI 6238/6239 User Manual...

  • Page 93: Counter N Gate Signal

    Each counter has independent input selectors for the Counter n Aux signal. Any of the following signals can be routed to the Counter n Aux input. • • • NI 6238/6239 User Manual RTSI <0..7> Input PFI <0..5> ai/ReferenceTrigger ai/StartTrigger...

  • Page 94: Counter N A, Counter N B, And Counter N Z Signals

    In other applications, such as single pulse-width measurement, the counter begins © National Instruments Corporation ai/StartTrigger PXI_STAR RTSI <0..7> Input PFI <0..5> PXI_STAR 7-29 Chapter 7 Counters NI 6238/6239 User Manual...

  • Page 95: Routing Signals To Counter N Hw Arm Input

    RTSI <0..7> terminal. All output PFIs are set to high-impedance at startup. Frequency Output Signal The Frequency Output (FREQ OUT) signal is the output of the frequency output generator. NI 6238/6239 User Manual RTSI <0..7> Input PFI <0..5> ai/ReferenceTrigger ai/StartTrigger...

  • Page 96: Routing Frequency Output To A Terminal

    M Series default PFI lines for counter functions are listed in Physical Channels in the NI-DAQmx Help or the LabVIEW 8.x Help. © National Instruments Corporation Table 7-4. NI 6238/6239 Device Default NI-DAQmx Counter/Timer Pins Counter/Timer Signal Default Pin Number (Name)

  • Page 97: Counter Triggering

    When using a pause trigger, the pause trigger source is routed to the Counter n Gate signal input of the counter. NI 6238/6239 User Manual 7-32 ni.com...

  • Page 98: Other Counter Features

    2.55 ms ~101,800 Disabled — 7-33 Chapter 7 Counters Pulse Width Pulse Width Guaranteed to Guaranteed to Pass Filter Not Pass Filter 125 ns 100 ns 6.425 µs 6.400 µs 2.55 ms 2.54 ms — — NI 6238/6239 User Manual...

  • Page 99: 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 6238/6239 User Manual Figure 7-29. Filter Example ni.com/info...

  • Page 100: Duplicate Count Prevention

    Duplicate Counting) Figure 7-31 shows an external buffered signal as the period measurement Source. © National Instruments Corporation External Signal Prescaler Rollover (Used as Source by Counter) Counter Value Figure 7-30. Prescaling 7-35 Chapter 7 Counters NI 6238/6239 User Manual...

  • Page 101: Example Application That Works Incorrectly (Duplicate Counting)

    (Duplicate Counting) In Figure 7-32, after the first rising edge of Gate, no Source pulses occur. So the counter does not write the correct data to the buffer. NI 6238/6239 User Manual Rising Edge of Gate Figure 7-31. Duplicate Count Prevention Example section.

  • Page 102: Example Application That Prevents Duplicate Count

    Figure 7-32. Duplicate Count Example Counter detects rising Gate edge. Figure 7-33. Duplicate Count Prevention Example 7-37 Chapter 7 Counters No Source edge, so no value written to buffer. Counter value increments only one time for each Source pulse. NI 6238/6239 User Manual...

  • Page 103: When To Use Duplicate Count Prevention

    In DAQmx, the device uses 80 MHz source mode if the user performs the following: • • NI 6238/6239 User Manual You are making a counter measurement You are using an external signal (such as PFI <0..5>) as the counter Source...

  • Page 104: 80 Mhz Source Mode

    Mode 80 MHz Source 80 MHz Source 80 MHz 80 MHz Source Timebase 20 MHz Other Internal Timebase, 100 Source kHz Timebase, or PXI_CLK10 Any Other External Source Signal (such as PFI or RTSI) Count NI 6238/6239 User Manual Counters...

  • Page 105: External Source Mode

    Source signal by several nanoseconds. The device synchronizes signals on the rising edge of the delayed Source signal, and counts on the following rising edge of the source, as shown in Figure 7-36. NI 6238/6239 User Manual Source Figure 7-35. Other Internal Source Mode...

  • Page 106: Pfi

    NI 6238/6239 devices have 10 Programmable Function Interface (PFI) signals—six input signals and four output signals. Each PFI <0..5>/P0.<0..5> can be configured as a timing input signal for AI or counter/timer functions or a static digital input. Each PFI input also has a programmable debouncing filter.

  • Page 107: Using Pfi Terminals As Timing Input Signals

    P0.x or P1.x. The voltage input and output levels and the current drive levels of the PFI signals are listed in the NI 6238/6239 Specifications. Using PFI Terminals as Timing Input Signals Use PFI <0..5> terminals to route external timing signals to many different M Series functions.

  • Page 108: Exporting Timing Output Signals Using Pfi Terminals

    • Note Short pulses on the signal might not be observable by the user or another instrument. Refer to the Digital Output (Port 1) section of the NI 6238/6239 Specifications for more information. Using PFI Terminals as Static Digital Inputs and Outputs When a terminal is used as a static digital input or output, it is called P0.x...

  • Page 109: 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 8-1. NI 6238/6239 User Manual I/O Connector PFI 2...

  • Page 110: I/O Protection

    To access this KnowledgeBase, go to code I/O Protection Each DI, DO, and PFI signal is protected against overvoltage and undervoltage conditions as well as ESD events on NI 6238/6239 devices. © National Instruments Corporation Table 8-1. Filters N (Filter...

  • Page 111: Programmable Power-Up States

    The DI signals P0.<0..5> are referenced to P0.GND and DO signals P1.<0..3> are referenced to P1.GND. Figures 8-5 and 8-6 show P0.<0..5> and P1.<0..3> on the NI 6238 and the NI 6239 device, respectively. Digital input and output signals can range from 0 to 30 V.
  • Page 112 P1.VCC P1.0 P1.1 P1.GND P0.0 P0.GND © National Instruments Corporation P1.<0..3> Digital Isolators P1.GND P0.GND Figure 8-5. NI 6238 Digital I/O Connections (DO Source) Chapter 8 NI 6238/6239 User Manual...
  • Page 113 P0.GND Caution Exceeding the maximum input voltage or maximum working voltage ratings, which are listed in the NI 6238/6239 Specifications, can damage the DAQ device and the computer. NI is not liable for any damage resulting from such signal connections.

  • Page 114: Isolation And Digital Isolators

    © National Instruments Corporation Table 9-1. Ground Symbols Isolated Ground Isolation Barrier AI GND Digital Routing and Clock AO GND Generation Digital Isolators RTSI P0.GND P1.GND Figure 9-1. General NI 6238/6239 Block Diagram Non-Isolated Ground Interface NI 6238/6239 User Manual...

  • Page 115: Digital Isolation

    All analog measurements are made relative to its isolated ground signal. Each isolated ground is an input to the NI 6238/6239 device. The user must connect this ground to the ground of system being measured or controlled.

  • Page 116: Reducing Common-Mode Noise

    Switching voltages through the transformer causes charging and discharging of the parasitic capacitances and inductances in the switching power supplies that occur on every switch cycle, resulting in high-speed currents flowing through the isolated side and returning to the non-isolated side, which is earth ground.

  • Page 117: Digital Routing And Clock Generation

    Routes and generates the main clock signals for the M Series device. 10 MHz RefClk ÷ 8 ÷ Figure 10-1. M Series Clock Routing Circuitry 10-1 (To RTSI <0..7> Output Selectors) 80 MHz Timebase 20 MHz Timebase ÷ 100 kHz Timebase NI 6238/6239 User Manual...

  • Page 118: 80 Mhz Timebase

    The following signals can be routed to drive the external reference clock. • • • The external reference clock is an input to a Phase-Lock Loop (PLL). The PLL generates the internal timebases. NI 6238/6239 User Manual Onboard oscillator External signal (by using the external reference clock) RTSI <0..7> PXI_CLK10 PXI_STAR 10-2 ni.com...

  • Page 119: 10 Mhz Reference Clock

    Real-Time System Integration (RTSI) is set of bused signals among devices that allow you to do the following. • © National Instruments Corporation Chapter 10 Use a common clock (or timebase) to drive the timing engine on multiple devices 10-3 Digital Routing and Clock Generation NI 6238/6239 User Manual...

  • Page 120: Rtsi Connector Pinout

    Chapter 10 Digital Routing and Clock Generation • Many National Instruments DAQ, motion, vision, and CAN devices support RTSI. In a PCI system, the RTSI bus consists of the RTSI bus interface and a ribbon cable. The bus can route timing and trigger signals between several functions on as many as five DAQ, vision, motion, or CAN devices in the computer.

  • Page 121: Using Rtsi As Outputs

    10 MHz Reference Clock Counter n Source, Gate, Z, Internal Output FREQ OUT Input PFI <0..5> 10-5 Digital Routing and Clock Generation Terminal 1–18 19, 21, 23, 25, 27, 29, 31, 33 NI 6238/6239 User Manual...

  • Page 122: Using Rtsi Terminals As Timing Input Signals

    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 10-2. NI 6238/6239 User Manual AI Convert Clock AI Sample Clock...

  • Page 123: Pxi Clock And Trigger Signals

    Not Pass Filter 125 ns 100 ns 6.425 µs 6.400 µs 2.55 ms 2.54 ms — — Filtered input goes high when terminal is sampled high on five consecutive filter clocks. and enter the info ni.com/info NI 6238/6239 User Manual...

  • Page 124: Pxi_Star Trigger

    Star Trigger feature. PXI_STAR Filters You can enable a programmable debouncing filter on each PFI, RTSI, or PXI_STAR signal. When the filters are enabled, your device samples the NI 6238/6239 User Manual 10-8 ni.com...
  • Page 125 Guaranteed to Guaranteed to Pass Filter Not Pass Filter 125 ns 100 ns 6.425 µs 6.400 µs 2.55 ms 2.54 ms — — Filtered input goes high when terminal is sampled high on five consecutive filter clocks. NI 6238/6239 User Manual...
  • Page 126 Refer to the KnowledgeBase document, Digital Filtering with M Series and CompactDAQ, for more information about digital filters and counters. To access this KnowledgeBase, go to code NI 6238/6239 User Manual rddfms 10-10 and enter the info ni.com/info...

  • Page 127: Dma Controllers

    Bus Interface The bus interface circuitry of NI 6238/6239 devices efficiently moves data between host memory and the measurement and acquisition circuits. NI 6238/6239 devices are available for the following platforms. • • NI 6238/6239 devices are jumperless for complete plug-and-play operation.

  • Page 128: Pxi_Star Filters

    PXI-1 devices use PCI signaling to communicate to the host controller (as opposed to PCI Express signaling). Peripheral devices are installed in peripheral slots and are not system controllers. NI 6238/6239 User Manual Triggers, sections of Chapter 10, ). Using the terminology of the PXI specifications, PXI chassis—PXI-6238/6239 devices can be installed in any...

  • Page 129: Using Pxi With Compactpci

    DMA is a method to transfer data between the device and computer memory without the involvement of the CPU. This method makes DMA the fastest available data transfer method. National Instruments uses DMA hardware and software technology to achieve high throughput rates and to increase system utilization.

  • Page 130: Interrupt Request (Irq)

    However, NI-DAQmx allows you to disable DMA and use interrupts. To change your data transfer mechanism between DMA and interrupts in NI-DAQmx, use the Data Transfer Mechanism property node. NI 6238/6239 User Manual section of Chapter 5, Analog Output, for more information.

  • Page 131: Triggering

    When you configure a trigger, you must decide how you want to produce the trigger and the action you want the trigger to cause. NI 6238/6239 devices support internal software triggering, as well as external digital triggering. For information about the different actions...
  • Page 132 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 6238/6239 User Manual Analog input acquisition Analog output generation Counter behavior 12-2...

  • Page 133: Device-Specific Information

    Device-Specific Information This appendix contains device pinouts, specifications, cable and accessory choices, and other information for the NI 6238 and isolated devices. To obtain documentation for devices not listed here, refer to ni.com/manuals NI 6238 NI 6238 Pinout Figure A-1 shows the pinout of the NI 6238.
  • Page 134 P1.VCC PFI 7/P1.1 (Output) PFI 9/P1.3 (Output) NC = No Connect Figure A-1. NI 6238 Pinout Table A-1. NI 6238 Device Default NI-DAQmx Counter/Timer Pins Counter/Timer Signal Default Pin Number (Name) 13 (PFI 0) 32 (PFI 1) 33 (PFI 2)

  • Page 135: Screw Terminal

    This section describes some cable and accessory options for the NI 6238 device. Refer to Screw Terminal National Instruments offers several styles of screw terminal connector blocks. Use an SH37F-37M cable to connect an NI 6238 device to a connector block, such as the following: • •...

  • Page 136: Ni 6239 Pinout

    Figure A-2 shows the pinout of the NI 6239. For a detailed description of each signal, refer to the Descriptions NI 6238/6239 User Manual SH37F-37M-x—37-pin female-to-male shielded I/O cable, UL Listed derated to 30 Vrms, 42.4 V , or 60 VDC R37F-37M-1—37-pin female-to-male ribbon I/O cable...
  • Page 137 AI 5– CAL– AI 6– AI 7– AO 1 PFI 0/P0.0 (Input) P0.GND PFI 3/P0.3 (Input) PFI 5/P0.5 (Input) PFI 6/P1.0 (Output) PFI 8/P1.2 (Output) P1.VCC Port P0.0 P0.1 P0.2 P1.0 P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 NI 6238/6239 User Manual...
  • Page 138 This section describes some cable and accessory options for the NI 6239 device. Refer to Screw Terminal National Instruments offers several styles of screw terminal connector blocks. Use an SH37F-37M cable to connect an NI 6239 device to a connector block, such as the following: •...
  • Page 139 SH37F-37M-x—37-pin female-to-male shielded I/O cable, UL Listed derated to 30 Vrms, 42.4 V , or 60 VDC R37F-37M-1—37-pin female-to-male ribbon I/O cable SH37F-P-4—37-pin female-to-pigtails shielded I/O cable Custom Cabling section of Chapter 2, Appendix A Device-Specific Information DAQ System Overview, NI 6238/6239 User Manual...

  • Page 140: Troubleshooting

    Check to make sure that the AI GND terminal is tied to a certain voltage level and verify that your input current signals are at voltage levels within the common-mode input range for this device. Refer to the NI 6238/6239 Specifications for more information about common-mode input range.

  • Page 141: Analog Output

    DAC code changes. 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 NI 6238/6239 User Manual Channel 0 Channel 1 Convert Period Sample Period Figure B-1.
  • Page 142 How do I connect counter signals to my M Series device? information on counter signal connections. © National Instruments Corporation Duplicate Count Prevention Default Counter Terminals section of Chapter 7, Counters, has Appendix B Troubleshooting section of Chapter 7, Counters, NI 6238/6239 User Manual...

  • Page 143: 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 144 Worldwide Offices section of office Web sites, which provide up-to-date contact information, support phone numbers, email addresses, and current events. NI 6238/6239 User Manual Calibration Certificate—If your product supports calibration, you can obtain the calibration certificate for your product at ni.com/calibration...
  • Page 145 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 6238/6239 User Manual...
  • Page 146 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 6238/6239 User Manual ni.com...
  • Page 147 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 6238/6239 User Manual...
  • Page 148 A symbol that connects points on a flowchart. convert rate Reciprocal of the interchannel delay. count The number of events, such as zero crossings, pulses, or cycles. NI 6238/6239 User Manual ni.com...
  • Page 149 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 6238/6239 User Manual...
  • Page 150 Static digital I/O refers to signals where the values are set and held, or rarely change. Dynamic digital I/O refers to digital systems where the signals are continuously changing, often at multi-MHz clock rates. digital isolator Provides voltage isolation between its input and output. NI 6238/6239 User Manual ni.com...
  • Page 151 A voltage pulse from an external source that causes a DAQ operation to begin. EXTREF External reference signal. © National Instruments Corporation Glossary NI 6238/6239 User Manual...
  • Page 152 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. NI 6238/6239 User Manual ni.com...
  • Page 153 2. The number of scans read or updates written per second. 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 6238/6239 User Manual...
  • Page 154 An electrical break between any two signals or planes up to a given voltage. isolation barrier An electrical break between two electrical planes providing a given or set amount of electrical isolation. Current does not flow or transfer between the two sides of the isolation barrier. NI 6238/6239 User Manual G-10 ni.com...
  • Page 155 An MIO product can be considered a miniature mixed signal tester, due to its broad range of signal types and flexibility. Also known as multifunction DAQ. © National Instruments Corporation = 1,000 Hz. Hz = 1,000,000 Hz. –6 G-11 Glossary NI 6238/6239 User Manual...
  • Page 156 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 157 2. A digital port, consisting of four or eight lines of digital input and/or output. posttriggering The technique used on a DAQ device to acquire a programmed number of samples after trigger conditions are met. © National Instruments Corporation instrumentation amplifier. G-13 Glossary NI 6238/6239 User Manual...
  • Page 158 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 159 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 160 (file system), handling of multiple programs at the same time (multi-tasking), network interconnection, printing, and keyboard/user interface interaction. software triggering A method of triggering in which you simulate an analog trigger using software. Also called conditional retrieval. NI 6238/6239 User Manual differential input. G-16 ni.com...
  • Page 161 Output delay time. transducer A device that responds to a physical stimulus (heat, light, sound, pressure, motion, flow, and so on), and produces a corresponding electrical signal. See also sensor. © National Instruments Corporation G-17 Glossary NI 6238/6239 User Manual...
  • Page 162 USB 2.0 retains compatibility with the original USB specification. Volts. Common-mode voltage. Ground loop voltage. Volts, input high. Volts, input low. Volts in. Measured voltage. Volts, output high. Volts, output low. Volts out. NI 6238/6239 User Manual G-18 ni.com...
  • Page 163 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 6238/6239 User Manual...
  • Page 164 4-12 timing signals, 4-12 triggering, 4-11 troubleshooting, B-1 analog output circuitry, 5-1 connecting current signals, 5-4 data generation methods, 5-2 getting started with applications in software, 5-10 signals, 5-5 timing signals, 5-5 trigger signals, 5-4 NI 6238/6239 User Manual...
  • Page 165 7-6 semi-period measurement, 7-10 two-signal edge-separation measurement, 7-20 interface, 11-1 RTSI, 10-3 NI 6238/6239 User Manual cables, 2-4, A-3, A-6 choosing for your device, 1-2 custom, 2-4 calibration certificate (NI resources), C-2 calibration circuitry, 2-3 cascading counters, 7-33...
  • Page 166 IRQ, 11-4 programmed I/O, 11-4 Declaration of Conformity (NI resources), C-1 default counter terminals, 7-31 device cabling, 2-4 information, A-1 multiple synchronization, 10-3 specifications, 1-2 diagnostic tools (NI resources), C-1 differential, analog input (troubleshooting), B-1 Index NI 6238/6239 User Manual...
  • Page 167 7-3 buffered, 7-4 non-cumulative buffered, 7-5 sample clock, 7-4 edge-separation measurement buffered two-signal, 7-20 single two-signal, 7-19 NI 6238/6239 User Manual enabling duplicate count prevention in NI-DAQmx, 7-38 encoders, quadrature, 7-16 encoding X1, 7-16 X2, 7-17 X4, 7-17...
  • Page 168 DAQ, 2-1 installing, 1-1 hardware-timed acquisitions, 4-10 generations, 5-2 help, technical support, C-1 I/O connector, 3-1 NI 6238 pinout, A-1 NI 6239 pinout, A-4 I/O protection, 6-1, 8-5 input signals using PFI terminals as, 8-2 using RTSI terminals as, 10-6 installation...
  • Page 169 NI-DAQmx, enabling duplicate count prevention, 7-38 non-buffered hardware-timed acquisitions, 4-11 generations, 5-3 non-cumulative buffered edge counting, 7-5 NI 6238/6239 User Manual other internal source mode, 7-39 other software, 1-1 output signals, glitches (troubleshooting), B-2 outputs, using RTSI as, 10-5 overview, 2-1...
  • Page 170 Counter n A, 7-29 Counter n Aux, 7-28 Counter n B, 7-29 Counter n Gate, 7-28 Counter n HW Arm, 7-29 Counter n Internal Output, 7-30 Counter n Source, 7-26 Counter n TC, 7-30 Counter n Up_Down, 7-29 Index NI 6238/6239 User Manual...
  • Page 171 C-1 synchronization modes, 7-38 80 MHz source, 7-39 external source, 7-40 other internal source, 7-39 NI 6238/6239 User Manual synchronizing multiple devices, 10-3 synchronous counting mode, 7-35 technical support, xviii, C-1 terminals, default counter, 7-31 Timebase 100 kHz, 10-2...
  • Page 172 10-6 using short high-quality cabling, 4-8 V-I Converter, 5-1 © National Instruments Corporation waveform generation signals, 5-5 Web resources, C-1 wiring, field, 4-11 X1 encoding, 7-16 X2 encoding, 7-17 X4 encoding, 7-17 Index NI 6238/6239 User Manual...

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