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Chapter 9

Isolation and Digital Isolators on USB-6215/6216/6218 Devices

National Instruments Corporation

9-2

NI USB-621x User Manual

The non-isolated gro

nd is connected to the chassis gro

nd of the PC.

Each isolated gro

nd is

not

connected to the chassis gro

nd of the PC.

The isolated gro

nd can be at a higher or lower voltage relative to the

non-isolated gro

nd. All analog meas

rements are made relative to the

isolated gro

nd signal.

The isolated gro

nd is an inp

t to the USB-6215/6216/6218 device. The

ser

must

connect this gro

nd to the gro

nd of system being meas

red or

controlled. For more information, refer to the following:

•

The

Connecting Analog Input Signals on USB-6215/6216/6218

Devices

section of Chapter 4,

Analog Input

•

The

Connecting Analog Output Signals

section of Chapter 5,

Analog

Output

•

The

Connecting Digital I/O Signals on USB-6210/6211/6215/6218

Devices

Connecting Digital I/O Signals on USB-6212/6216 Devices

section of Chapter 6,

Digital I/O

•

The

Connecting PFI Input Signals

section of Chapter 7,

PFI

Digital Isolation

USB-6215/6216/6218 devices

se digital isolators. Unlike analog isolators,

digital isolators do not introd

ce any analog error in the meas

rements

taken by the device. The A/D converter,

sed for analog inp

t, is on the

isolated side of the device. The analog inp

ts are digitized before they are

sent across the isolation barrier. Similarly, the D/A converters,

sed for

analog o

t, are on the isolated side of the device.

Benefits of an Isolated DAQ Device

With isolation, engineers can safely meas

re a small signal in the presence

of a large common-mode voltage signal. Some advantages of isolation are
as follows:

•

Improved rejection

—Isolation increases the ability of the

meas

rement system to reject common-mode voltages.

Common-mode voltage is the signal that is present or “common”
to both the positive and negative inp

t of a meas

rement device, b

is not part of the signal to be meas

red.

•

Improved accuracy

—Isolation improves meas

rement acc

racy by

physically preventing gro

nd loops. Gro

nd loops, a common so

rce

Содержание Data Acquisition Device NI USB-621x

Страница 1: ...DAQ M Series NI USB 621x User Manual Bus Powered M Series USB Devices NI USB 621x User Manual ni com manuals Deutsch Français March 2008 371931E 01 ...

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Страница 3: ...orm electronic or mechanical including photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National 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 soft...

Страница 4: ...nt of Communications DOC Changes or modifications not expressly approved by NI could void the user s authority to operate the equipment under the FCC Rules Class A Federal Communications Commission This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC Rules These limits are designed to provide reasonable protection against ha...

Страница 5: ... Relief 1 3 Mounting the USB 621x 1 4 Desktop Use 1 4 DIN Rail Mounting 1 4 Panel Mounting 1 5 Chapter 2 DAQ System Overview DAQ Hardware 2 1 DAQ STC2 2 2 Calibration Circuitry 2 2 Signal Conditioning 2 3 Sensors and Transducers 2 3 Cables and Accessories 2 4 USB 621x Mass Termination Custom Cabling 2 4 Programming Devices in Software 2 5 Chapter 3 Connector and LED Information I O Connector Signa...

Страница 6: ... from Sample Clock to Convert Clock 4 17 Other Timing Requirements 4 17 AI Convert Clock Timebase Signal 4 19 AI Hold Complete Event Signal 4 19 AI Start Trigger Signal 4 20 Using a Digital Source 4 20 Routing AI Start Trigger to an Output Terminal 4 20 AI Reference Trigger Signal 4 21 Using a Digital Source 4 22 Routing AI Reference Trigger to an Output Terminal 4 22 AI Pause Trigger Signal 4 22 ...

Страница 7: ... Connections for Ground Referenced Signal Sources 4 34 Connecting Analog Input Signals on USB 6215 6216 6218 Devices 4 36 Taking Differential Measurements 4 36 Taking Referenced Single Ended RSE Measurements 4 37 Taking Non Referenced Single Ended NRSE Measurements 4 38 Chapter 5 Analog Output AO Range 5 2 Minimizing Glitches on the Output Signal 5 2 Analog Output Data Generation Methods 5 2 Analo...

Страница 8: ...reasing Current Drive on USB 6212 6216 Devices 6 6 Connecting Digital I O Signals on USB 6212 6216 Devices 6 6 Getting Started with DIO Applications in Software on USB 6212 6216 Devices 6 7 Chapter 7 PFI Using PFI Terminals as Timing Input Signals 7 2 Exporting Timing Output Signals Using PFI Terminals 7 3 Using PFI Terminals as Static Digital I Os 7 3 Connecting PFI Input Signals 7 4 PFI Filters ...

Страница 9: ...se Train Generation 8 22 Frequency Generation 8 23 Using the Frequency Generator 8 23 Frequency Division 8 24 Pulse Generation for ETS 8 24 Counter Timing Signals 8 25 Counter n Source Signal 8 26 Routing a Signal to Counter n Source 8 26 Routing Counter n Source to an Output Terminal 8 26 Counter n Gate Signal 8 27 Routing a Signal to Counter n Gate 8 27 Routing Counter n Gate to an Output Termin...

Страница 10: ...abling Duplicate Count Prevention in NI DAQmx 8 37 Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices Digital Isolation 9 2 Benefits of an Isolated DAQ Device 9 2 Reducing Common Mode Noise 9 3 Creating an AC Return Path 9 3 Isolated Systems 9 4 Non Isolated Systems 9 4 Chapter 10 Digital Routing and Clock Generation 80 MHz Timebase 10 1 20 MHz Timebase 10 1 100 kHz Timebase 1...

Страница 11: ... A 6 USB 6212 6216 Mass Termination A 8 USB 6218 A 13 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 4 Figure A 3 USB 6212 6216 Screw Terminal Pinout A 6 Figure A 4 USB 6212 6216 Mass Termination Pinout A 9 Figure A 5 USB 6218 Pinout A 13 ...

Страница 12: ...menu select the Page Setup item and select Options from the last dialog box This icon denotes a note which alerts you to important information This icon denotes a caution which advises you of precautions to take to avoid injury data loss or a system crash When this symbol is marked on a product refer to the Read Me First Safety and Radio Frequency Interference for information about precautions to ...

Страница 13: ...ersion 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 Select Start All Programs National Instruments NI DAQ NI DAQmx Help NI DAQmx Base Linux Mac OS X LabVIEW PDA 8 x The NI DAQmx Base Getting Star...

Страница 14: ...se to build data acquisition and instrument control applications Open the Getting Started with LabVIEW manual by selecting Start All Programs National Instruments LabVIEW LabVIEW Manuals or by navigating to the labview manuals directory and opening LV_Getting_Started pdf Use the LabVIEW Help available by selecting Help Search the LabVIEW Help in LabVIEW to access information about LabVIEW programm...

Страница 15: ... Studio NET You can generate the configuration code based on your task or channel in Measurement Studio Refer to the DAQ Assistant Help for additional information about generating code You also can create channels and tasks and write your own applications in your ADE using the NI DAQmx API For help with NI DAQmx methods and properties refer to the NI DAQmx NET Class Library or the NI DAQmx Visual ...

Страница 16: ...I overview measurement tasks and concepts and function reference This help is fully integrated into the Visual Studio NET documentation To view the NI DAQmx NET documentation go to Start Programs National Instruments NI DAQ NI DAQmx NET Reference Help Expand NI Measurement Studio Help NI Measurement Studio NET Class Library Reference to view the function reference Expand NI Measurement Studio Help...

Страница 17: ...tain a detailed course outline refer to ni com training Technical Support on the Web For additional support refer to ni com support or zone ni com Note You can download these documents at ni com manuals DAQ specifications and manuals are available as PDFs You must have Adobe Acrobat Reader with Search and Accessibility 5 0 5 or later installed to view the PDFs Refer to the Adobe Systems Incorporat...

Страница 18: ...ware you plan to use with the device Installing NI DAQmx The NI DAQmx for USB Devices Getting Started Guide which you can download from ni com manuals offers NI DAQmx users step by step instructions for installing software and hardware configuring channels and tasks and getting started developing an application Installing Other Software If you are using other software refer to the installation ins...

Страница 19: ... the combicon connectors on USB 621x Screw Terminal devices You can choose labels with pin numbers or signal names or blank labels Choose one of the labels align the correct label with the terminals printed on the top panel of your device or the 16 position combicon connector and apply the label as shown in Figure 1 1 Figure 1 1 USB 621x Signal Labels 1 Terminal Number Label 2 Single Ended Signal ...

Страница 20: ... two grooves on the underside of the USB 621x Choose the USB cable groove that matches your USB cable size as shown in Figure 1 2a Zip Tie Method Thread a zip tie through the zip tie bar on the underside of the USB 621x and tighten around the USB cable as shown in Figure 1 2b Figure 1 2 USB Cable Strain Relief Options 1 USB Cable Strain Relief Groove Large 2 USB Cable Strain Relief Groove Small 3 ...

Страница 21: ...pplied rubber non skid feet to the underside of the device as shown in Figure 1 3 Note Do not apply the rubber feet if you are panel mounting the USB 621x or stacking the device on another USB 621x device Figure 1 3 Applying Rubber Feet to the USB 621x DIN Rail Mounting The DIN rail mounting kit part number 779689 01 not included in your USB 621x kit is an accessory you can use to mount the USB 62...

Страница 22: ...rain relief as described in the USB Cable Strain Relief section before panel mounting the USB 621x 1 Download and print the panel mounting template PDF attached in the KnowledgeBase document USB 621x Panel Mounting Template Go to ni com info and enter the info code ex3x98 to locate the KnowledgeBase 2 Using the template mark the bottom point and top point on the panel USB 621x Screw Terminal Devic...

Страница 23: ...able from the connector on the USB 621x 4 Screw a 8 or M4 screw into the bottom point on the panel 5 Set the USB 621x on the screw by fitting it into the bottom screw notch on the underside of the USB 621x 6 Screw a 8 or M4 screw through the USB 621x top screw hole into the panel ...

Страница 24: ...nal conditioning devices and a cable for accessory connection The following sections contain more information about the components of a typical DAQ system Figure 2 1 Components of a Typical DAQ System DAQ Hardware DAQ hardware digitizes signals performs D A conversions to generate analog output signals and measures and controls digital I O signals Figure 2 2 features components common to all USB 6...

Страница 25: ... gating Static DI DO and DIO signals USB Hi Speed 2 0 interface Up to four USB Signal Streams for acquisition and generation functions Calibration Circuitry The USB 621x analog inputs and outputs have calibration circuitry to correct gain and offset errors 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 a...

Страница 26: ...and multiplexing In addition many transducers require excitation currents or voltages bridge completion linearization or high amplification for proper and accurate operation Therefore most computer based measurement systems include some form of signal conditioning in addition to plug in data acquisition DAQ devices Sensors and Transducers Sensors can generate electrical signals to measure physical...

Страница 27: ...mination Cables and Accessories section of Appendix A Device Specific Information for a list of cables and accessories for USB 621x Mass Termination devices USB 621x Mass Termination Custom Cabling NI offers cables and accessories for many applications However if you want to develop your own cable adhere to the following guidelines for best results For AI signals use shielded twisted pair wires fo...

Страница 28: ...es a collection of programming examples to help you get started developing an application You can modify example code and save it in an application You can use examples to develop a new application or add example code to an existing application To locate LabVIEW and LabWindows CVI examples open the National Instruments Example Finder In LabVIEW select Help Find Examples In LabWindows CVI select He...

Страница 29: ...put Ground These terminals are the reference point for single ended AI measurements in RSE mode and the bias current return point for DIFF measurements All three ground references AI GND AO GND and D GND are connected on the device AI 0 31 Varies Input Analog Input Channels 0 to 31 For single ended measurements each signal is an analog input voltage channel In RSE mode AI GND is the reference for ...

Страница 30: ...10 6211 6215 6218 Devices Programmable Function Interface or Static Digital Output Channels 0 to 7 You can route many different internal AI AO or counter timer outputs to each PFI terminal You also can use these terminals as static digital output lines P0 0 15 D GND Input or Output USB 6212 6216 Devices Port 0 Digital I O Channels 0 to 15 You can individually configure each signal as an input or o...

Страница 31: ...are protected against undervoltage and overvoltage and they have a fuse to protect them from short circuit conditions1 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 USB Device Fuse Replacement USB 621x Mass Termination Devices USB 621x Mass Termination devices have a replaceable 0 75A 125V fuse L...

Страница 32: ... Mass Termination Fuse Location 4 Replace the device top and reattach with the screws Note Unscrewing and reinstalling the thread forming screws over time will produce a compromised connection between the device top and bottom 1 0 75A 125V Fuse Socketed 1 N A T I O N A L I N S T R U M E N T S N I U S B 6 2 1 6 1 6 I n p u t s 1 6 b i t 4 0 0 k S s I s o l a t o e d M u l t i f u n c t i o n I O ...

Страница 33: ... State Device Status Not lit Device not powered or device error Refer to ni com support if device is powered On not blinking Device error Refer to ni com support Single blink Operating normally Connected to USB Hi Speed port Refer to the NI USB 621x Specifications for more information Double blink Connected to USB Full Speed port Device performance might be affected Refer to the NI USB 621x Specif...

Страница 34: ... Specific Information for device I O connector pinouts Mux Each USB 621x device has one analog to digital converter ADC The multiplexers mux route one AI channel at a time to the ADC through the NI PGIA AI Ground Reference Settings The analog input ground reference settings circuitry selects between differential DIFF referenced single ended RSE and non referenced single ended NRSE input modes Each...

Страница 35: ...operations with DMA interrupts or programmed I O Isolation Barrier and Digital Isolators Refer to Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices for more information Analog Input Range The input range affects the resolution of the USB 621x device for an AI channel For example a 16 bit ADC converts analog inputs into one of 65 536 216 codes that is one of 65 536 possible di...

Страница 36: ...SENSE input The AI ground reference setting determines how you should connect your AI signals to the USB 621x device For more information refer to one of the following sections depending on your device Connecting Analog Input Signals on USB 6210 6211 6212 Devices Connecting Analog Input Signals on USB 6215 6216 6218 Devices Ground reference settings are programmed on a per channel basis For exampl...

Страница 37: ...eferred to as AI terminal configuration Caution The maximum input voltages rating of AI signals with respect to AI GND and for differential signals with respect to each other are listed in the NI USB 621x Specifications Exceeding the maximum input voltage of AI signals distorts the measurement results Exceeding the maximum input voltage rating also can damage the device and the computer NI is not ...

Страница 38: ...urement using the NI DAQmx C API set the terminalConfig property Refer to the NI DAQmx C Reference Help for more information Multichannel Scanning Considerations USB 621x devices can scan multiple channels at high rates and digitize the signals accurately However you should consider several issues when designing your measurement system to ensure the high accuracy of your measurements In multichann...

Страница 39: ...wer circuit external to your DAQ device to decrease the impedance seen by the DAQ device Refer to the KnowledgeBase document How Do I Create a Buffer to Decrease the Source Impedance of My Analog Input Signal by going to ni com info and entering the info code rdbbis Use Short High Quality Cabling Using short high quality cables can minimize several effects that degrade accuracy including crosstalk...

Страница 40: ...gain the example above where a 4 V signal is connected to channel 0 and a 1 mV signal is connected to channel 1 Suppose the input range for channel 0 is 10 V to 10 V and the input range of channel 1 is 200 mV to 200 mV You can connect channel 2 to AI GND or you can use the internal ground signal refer to Internal Channels in the NI DAQmx Help Set the input range of channel 2 to 200 mV to 200 mV to...

Страница 41: ...settle from 8 μs to 4 μs In some cases the slower scan rate system returns more accurate results Example 2 If the time relationship between channels is not critical you can sample from the same channel multiple times and scan less frequently For example suppose an application requires averaging 100 points from channel 0 and averaging 100 points from channel 1 You could alternate reading between ch...

Страница 42: ...one point at a time One property of buffered I O operations is the sample mode The sample mode can be either finite or continuous Finite sample mode acquisition refers to the acquisition of a specific predetermined number of data samples After the specified number of samples has been read in the acquisition stops If you use a reference trigger you must use finite sample mode Continuous acquisition...

Страница 43: ...wing recommendations apply mainly to AI signal routing to the device although they also apply to signal routing in general Minimize noise pickup and maximize measurement accuracy by taking the following precautions Use DIFF AI connections to reject common mode noise Use individually shielded twisted pair wires to connect AI signals to the device With this type of wire the signals attached to the p...

Страница 44: ...igure 4 4 Analog Input Timing Options USB 621x devices use AI Sample Clock ai SampleClock and AI Convert Clock ai ConvertClock to perform interval sampling As Figure 4 5 shows AI Sample Clock controls the sample period which is determined by the following equation 1 Sample Period Sample Rate 20 MHz Timebase 100 kHz Timebase Programmable Clock Divider Programmable Clock Divider AI Sample Clock Time...

Страница 45: ...or two channels at 125 kS s per channel illustrates the relationship Posttriggered data acquisition allows you to view only data that is acquired after a trigger event is received A typical posttriggered DAQ sequence is shown in Figure 4 6 The sample counter is loaded with the specified number of posttrigger samples in this example five The value decrements with each pulse on AI Sample Clock until...

Страница 46: ...le Clock until the value reaches zero The sample counter is then loaded with the number of posttriggered samples in this example three Figure 4 7 Pretriggered Data Acquisition Example If an AI Reference Trigger ai ReferenceTrigger pulse occurs before the specified number of pretrigger samples are acquired the trigger pulse is ignored Otherwise when the AI Reference Trigger pulse occurs the sample ...

Страница 47: ...ample clock timebase Using an External Source Use any input PFI line as the source of AI Sample Clock Routing AI Sample Clock to an Output Terminal You can route AI Sample Clock out to any output PFI terminal This pulse is always active high You can specify the output to have one of two behaviors With the pulse behavior your DAQ device briefly pulses the PFI terminal once for every occurrence of A...

Страница 48: ...I Convert Clock Signal section for more information about the timing requirements between AI Convert Clock and AI Sample Clock Figure 4 8 shows the relationship of AI Sample Clock to AI Start Trigger Figure 4 8 AI Sample Clock and AI Start Trigger AI Sample Clock Timebase Signal You can route any of the following signals to be the AI Sample Clock Timebase ai SampleClockTimebase signal 20 MHz Timeb...

Страница 49: ...ding NI DAQmx chooses the conversion rate so that the AI Convert Clock pulses are evenly spaced throughout the sample To explicitly specify the conversion rate use AI Convert Clock Rate DAQmx Timing property node or function Caution Setting the conversion rate higher than the maximum rate specified for your device will result in errors Using an Internal Source One of the following internal signals...

Страница 50: ...ts are met For example the device ignores both AI Sample Clock and AI Convert Clock until it receives a valid AI Start Trigger signal Once the device recognizes an AI Sample Clock pulse it ignores subsequent AI Sample Clock pulses until it receives the correct number of AI Convert Clock pulses Similarly the device ignores all AI Convert Clock pulses until it recognizes an AI Sample Clock pulse Onc...

Страница 51: ...rt Clock Pulses Are Gated Off Figure 4 12 AI Sample Clock and AI Convert Clock Improperly Matched Leads To Aperiodic Sampling AI Sample Clock AI Convert Clock Sample 1 Sample 2 Sample 3 Channel Measured 1 2 3 0 1 2 3 0 1 2 3 0 AI Sample Clock AI Convert Clock Sample 1 Sample 2 Sample 3 1 2 3 0 1 2 3 0 1 2 3 0 Channel Measured AI Sample Clock AI Convert Clock Sample 1 Sample 2 Sample 3 1 2 3 0 0 Ch...

Страница 52: ...k Timebase ai ConvertClockTimebase signal is divided down to provide one of the possible sources for AI Convert Clock Use one of the following signals as the source of AI Convert Clock Timebase AI Sample Clock Timebase 20 MHz Timebase AI Convert Clock Timebase is not available as an output on the I O connector AI Hold Complete Event Signal The AI Hold Complete Event ai HoldCompleteEvent signal gen...

Страница 53: ...gger is sometimes referred to as a posttriggered acquisition Using a Digital Source To use AI Start Trigger with a digital source specify a source and an edge The source can be any of the following signals USB 6210 6211 6215 Devices PFI 0 3 USB 6212 6216 Devices PFI 0 15 USB 6218 Devices PFI 0 3 PFI 8 11 Counter n Internal Output The source also can be one of several other internal signals on your...

Страница 54: ...ger samples the DAQ device begins to look for the reference trigger condition If the reference trigger condition occurs before the DAQ device captures the specified number of pretrigger samples the DAQ device ignores the condition If the buffer becomes full the DAQ device continuously discards the oldest samples in the buffer to make space for the next sample This data can be accessed with some li...

Страница 55: ...to pause and resume a measurement acquisition The internal sample clock pauses while the external trigger signal is active and resumes when the signal is inactive You can program the active level of the pause trigger to be high or low Using a Digital Source To use AI Sample Clock specify a source and a polarity The source can be any input PFI signal The source also can be one of several other inte...

Страница 56: ...t programming analog input applications and triggers in software refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later Connecting Analog Input Signals on USB 6210 6211 6212 Devices Table 4 2 summarizes the recommended input configuration for both types of signal sources on USB 6210 6211 6212 devices ...

Страница 57: ...ingle Ended NRSE Referenced Single Ended RSE Refer to the Analog Input Ground Reference Settings section for descriptions of the RSE NRSE and DIFF modes and software considerations Refer to the Connecting Ground Referenced Signal Sources section for more information AI AI AI GND Signal Source DAQ Device AI AI AI GND Signal Source DAQ Device Vcm AI AI SENSE AI GND Signal Source DAQ Device AI AI SEN...

Страница 58: ... to the device are greater than 3 m 10 ft The input signal requires a separate ground reference point or return signal The signal leads travel through noisy environments Two analog input channels AI and AI are available for the signal DIFF signal connections reduce noise pickup and increase common mode noise rejection DIFF signal connections also allow input signals to float within the common mode...

Страница 59: ...Referenced Single Ended NRSE Connections with Floating Signal Sources Only use NRSE input connections if the input signal meets the following conditions 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 DIFF input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditi...

Страница 60: ...Floating Signal Sources without Bias Resistors However for larger source impedances this connection leaves the DIFF signal path significantly off balance Noise that couples electrostatically onto the positive line does not couple onto the negative line because it is connected to ground This noise appears as a DIFF mode signal instead of a common mode signal and thus appears in your data In this ca...

Страница 61: ...USB 6210 6211 6212 device as shown in Figure 4 18 This fully balanced configuration offers slightly better noise rejection but has the disadvantage of loading the source down with the series combination 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 R is about 100...

Страница 62: ...ad the source but small enough not to produce significant input offset voltage as a result of input bias current typically 100 kΩ to 1 MΩ In this case connect the negative input directly to AI GND If the source has high output impedance balance the signal path as previously described using the same value resistor on both the positive and negative inputs be aware that there is some gain error from ...

Страница 63: ...ure 4 20 NRSE Connections for Floating Signal Sources All of the bias resistor configurations discussed in the Using Differential Connections for Floating Signal Sources section apply to the NRSE bias resistors as well Replace AI with AI SENSE in Figures 4 16 4 17 4 18 and 4 19 for configurations with zero to two bias resistors The noise rejection of NRSE mode is better than RSE mode because the A...

Страница 64: ...stant Connecting Ground Referenced Signal Sources What Are Ground Referenced Signal Sources A ground referenced signal source is a signal source connected to the building system ground It is already connected to a common ground point with respect to the device assuming that the computer is plugged into the same power system as the source Non isolated outputs of instruments and devices that plug in...

Страница 65: ...and AI are available DIFF signal connections reduce noise pickup and increase common mode noise rejection DIFF signal connections also allow input signals to float within the common mode limits of the NI PGIA Refer to the Using Differential Connections for Ground Referenced Signal Sources section for more information about differential connections When to Use Non Referenced Single Ended NRSE Conne...

Страница 66: ...rence between the signal source and the device ground Refer to the Using Non Referenced Single Ended NRSE Connections for Ground Referenced Signal Sources section for more information about NRSE connections When to Use Referenced Single Ended RSE Connections with Ground Referenced Signal Sources Do not use RSE connections with ground referenced signal sources Use NRSE or DIFF connections instead A...

Страница 67: ...und shown as Vcm in the figure AI and AI must both remain within 11 V of AI GND Using Non Referenced Single Ended NRSE Connections for Ground Referenced Signal Sources Figure 4 23 shows how to connect ground reference signal sources to the USB 6210 6211 6212 device in NRSE mode USB 6210 6211 6212 Configured in DIFF Mode PGIA Vcm Vs Ground Referenced Signal Source Common Mode Noise and Ground Poten...

Страница 68: ...een the device ground and the signal ground appears as a common mode signal at both the positive and negative inputs of the NI PGIA and this difference is rejected by the amplifier If the input circuitry of a device were referenced to ground as it is in the RSE ground reference setting this difference in ground potentials would appear as an error in the measured voltage Using the DAQ Assistant you...

Страница 69: ...GND unconnected you cannot ensure that AI 0 31 are within 10 V of AI GND and your measurement may be unreliable Taking Differential Measurements To attain more accurate measurements and less noise use a differential measurement configuration A differential measurement configuration requires two inputs for each measurement The AI 0 31 description in Table 3 1 I O Connector Signals lists the signal ...

Страница 70: ...ion allows the USB 6215 6216 6218 to take measurements on all AI channels when all channels share a common ground Figure 4 25 shows an RSE connection configuration Note If you leave the AI GND pin unconnected the signals float outside the working input range of the USB 6215 6216 6218 This can result in unreliable measurements because you cannot ensure that the input signal is within 10 V of AI GND...

Страница 71: ...ve input of the instrumentation amplifier PGIA that is shared among all channels configured for NRSE mode The behavior of this configuration is similar to that of RSE connections except it provides improved noise rejection Figure 4 26 shows an NRSE connection configuration Figure 4 26 Connecting to the USB 6215 6216 6218 in NRSE Mode In NRSE connection configuration each input channel is measured ...

Страница 72: ...SB 621x devices Figure 5 1 USB 621x Analog Output Circuitry The main blocks featured in the USB 621x analog output circuitry are as follows DAC0 and DAC1 Digital to analog converters DACs convert digital codes to analog voltages AO FIFO The AO FIFO enables analog output waveform generation It is a first in first out FIFO memory buffer between the computer and the DACs It allows you to download the...

Страница 73: ...tches depending on the frequency and nature of the output signal Visit ni com support for more information about minimizing glitches Analog Output Data Generation Methods When performing an analog output operation you can perform software timed or hardware timed generations Software timed generations Software controls the rate at which data is generated Software sends a separate command to the har...

Страница 74: ...nt methods of continuous generation that control what data is written These methods are regeneration FIFO regeneration and non regeneration modes Regeneration is the repetition of the data that is already in the buffer Standard regeneration is when data from the PC buffer is continually downloaded to the FIFO to be written out New data can be written to the PC buffer at any time without disrupting...

Страница 75: ...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 5 2 shows how to make AO connections to the device Figure 5 2 Analog Output Connections Analog Output Timing Signals Figure 5 3 summarizes all of the timing options provided by the analog output timing engine Load Load V OUT V OUT AO GND AO 1 Analog Output Channels USB 621x Device AO 0 Ch...

Страница 76: ...er signal to initiate a waveform generation If you do not use triggers you can begin a generation with a software command Using a Digital Source To use AO Start Trigger specify a source and an edge The source can be one of the following signals A pulse initiated by host software USB 6211 6215 Devices PFI 0 3 USB 6212 6216 Devices PFI 0 15 USB 6218 Devices PFI 0 3 PFI 8 11 AI Start Trigger ai Start...

Страница 77: ... Clock Timebase for example when you choose the onboard 20 MHz or 100 kHz Timebase the AO Sample Clock Timebase is divided down by a programmable clock divider circuit and then drives AO Sample Clock as shown in Figure 5 3 In this case AO Pause Trigger masks off AO Sample Clock Timebase pulses from the programmable clock divider For example an internal timebase is routed to AO Sample Clock Timebas...

Страница 78: ...AX in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information You also can specify whether the samples are paused when AO Pause Trigger is at a logic high or low level AO Sample Clock Signal Use the AO Sample Clock ao SampleClock signal to initiate AO samples Each sample updates the outputs of all of the DACs You can specify an internal or external source for AO Sample C...

Страница 79: ...es When using an internally generated AO Sample Clock you also can specify a configurable delay from AO Start Trigger to the first AO Sample Clock pulse By default this delay is two ticks of AO Sample Clock Timebase Figure 5 6 shows the relationship of AO Sample Clock to AO Start Trigger Figure 5 6 AO Sample Clock and AO Start Trigger AO Sample Clock Timebase Signal The AO Sample Clock Timebase ao...

Страница 80: ...signal then you should use AO Sample Clock rather than AO Sample Clock Timebase Getting Started with AO Applications in Software You can use a USB 621x device in the following analog output applications Single point on demand generation Finite generation Continuous generation Waveform generation You can perform these generations through programmed I O or USB Signal Stream data transfer mechanisms ...

Страница 81: ...s have up to eight static digital output lines P1 0 7 These lines also can be used as PFI output By default the digital output lines are disabled high impedance with a 47 kΩ pull down resistor on power up Software can enable or disable the entire port software cannot enable individual lines Once the port is enabled you can individually configure each line to the following Set a line to a static 0 ...

Страница 82: ...6210 6211 6215 6218 Devices Each DI DO and PFI signal is protected against overvoltage undervoltage and overcurrent conditions as well as ESD events However you should avoid these fault conditions by following these guidelines Do not connect a DO or PFI output lines to any external signal source ground signal or power supply Understand the current requirements of the load connected to DO or PFI ou...

Страница 83: ...ude receiving TTL signals and sensing external device states such as the state of the switch shown in the figure Digital output applications include sending TTL signals and driving external devices such as the LED shown in Figure 6 2 Figure 6 2 USB 6210 6211 6215 6218 Digital I O Connections Caution Exceeding the maximum input voltage ratings which are listed in the NI USB 621x Specifications can ...

Страница 84: ...B 6212 6216 Devices USB 6212 6216 devices contain Up to 16 DIO signals P0 0 15 Each signal can be individually configured as either Static digital input Static digital output 16 PFI DIO signals PFI 0 7 P1 0 7 and PFI 8 15 P2 0 7 Each signal can be individually configured as either Static digital input Static digital output PFI input PFI output Each pin is called PFI x when used as a PFI each pin i...

Страница 85: ... avoid these fault conditions by following these guidelines If you configure a PFI or DIO line as an output do not connect it to any external signal source ground signal or power supply If you configure a PFI or DIO line as an output understand the current requirements of the load connected to these signals Do not exceed the specified current output limits of the DAQ device NI has several signal c...

Страница 86: ... more information about setting power up states in NI DAQmx or MAX Increasing Current Drive on USB 6212 6216 Devices The total internal current limit for digital outputs and power drawn from the 5 V terminals is 50 mA You can increase this internal current limit by supplying an external 5 V supply Refer to the 5 V Power as an Input section of Chapter 3 Connector and LED Information Connecting Digi...

Страница 87: ... Applications in Software on USB 6212 6216 Devices You can use the USB 6212 6216 device in the following digital I O applications Static digital input Static digital output Note For more information about programming digital I O applications and triggers in software refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later 5 V LED TTL Signal 5 V Switch I O Connector D GND USB 6212 621...

Страница 88: ...onfigured as the following A static digital output A timing output signal from AI AO or counter timer functions Note USB 6212 6216 Devices PFI signals on USB 6212 6216 devices can be configured as input or output Each PFI input also has a programmable debouncing filter Figure 7 1 shows the circuitry of an input PFI line Figure 7 1 USB 621x PFI Input Circuitry Static DI I O Protection To Input Timi...

Страница 89: ...sing PFI Terminals as Timing Input Signals Use PFI terminals to route external timing signals to many different USB 621x functions Each input PFI terminal can be routed to any of the following signals AI Convert Clock ai ConvertClock AI Sample Clock ai SampleClock AI Start Trigger ai StartTrigger AI Reference Trigger ai ReferenceTrigger AI Pause Trigger ai PauseTrigger AI Sample Clock Timebase ai ...

Страница 90: ...i HoldCompleteEvent AI Reference Trigger ai ReferenceTrigger AI Sample Clock ai SampleClock AI Start Trigger ai StartTrigger AO Sample Clock ao SampleClock AO Start Trigger ao StartTrigger Counter n Source Counter n Gate Counter n Internal Output Frequency Output Note Signals with a are inverted before being driven to a terminal that is these signals are active low Using PFI Terminals as Static Di...

Страница 91: ...ers You can enable a programmable debouncing filter on each PFI signal When the filters are enabled your device samples the input on each rising edge of a filter clock USB 621x devices use an onboard oscillator to generate the filter clock with a 40 MHz frequency Note NI DAQmx only supports filters on counter inputs The following is an example of low to high transitions of the input signal High to...

Страница 92: ...5 ns N 5 Figure 7 4 Filter Example Enabling filters introduces jitter on the input signal For the 125 ns and 6 425 μs filter settings the jitter is up to 25 ns On the 2 56 ms setting the jitter is up to 10 025 μs Refer to the KnowledgeBase document Digital Filtering with M Series for more information about digital filters and counters To access this KnowledgeBase go to ni com info and enter the in...

Страница 93: ...s have a smaller operating range than the AI signals Treat the DAQ device as you would treat any static sensitive device Always properly ground yourself and the equipment when handling the DAQ device or connecting to it Programmable Power Up States At system startup and reset the hardware sets all output PFI and DO lines to high impedance by default The DAQ device does not drive the signal high or...

Страница 94: ... 621x Counters Counter 0 Counter 0 Source Counter 0 Timebase Counter 0 Aux Counter 0 HW Arm Counter 0 A Counter 0 B Counter 0 Up_Down Counter 0 Z Counter 0 Gate Counter 0 Internal Output Counter 0 TC Input Selection Muxes Frequency Generator Frequency Output Timebase Freq Out Input Selection Muxes Counter 1 Counter 1 Source Counter 1 Timebase Counter 1 Aux Counter 1 HW Arm Counter 1 A Counter 1 B ...

Страница 95: ...gle point on demand edge counting the counter counts the number of edges on the Source input after the counter is armed On demand refers to how the software can read the counter contents at any time without disturbing the counting process Figure 8 2 shows an example of single point edge counting Figure 8 2 Single Point On Demand Edge Counting You also can use a pause trigger to pause or gate the c...

Страница 96: ... count values returned are the cumulative counts since the counter armed event that is the sample clock does not reset the counter You can route the counter sample clock to the Gate input of the counter You can configure the counter to sample on the rising or falling edge of the sample clock Figure 8 4 shows an example of buffered edge counting Notice that counting begins when the counter is armed...

Страница 97: ...ith a known period to the Source input of the counter The counter counts the number of rising or falling edges on the Source signal while the pulse on the Gate signal is active You can calculate the pulse width by multiplying the period of the Source signal by the number of edges returned by the counter A pulse width measurement is accurate even if the counter is armed while a pulse train is in pr...

Страница 98: ...while the Gate input remains active On each trailing edge of the Gate signal the counter stores the count in a hardware save register A USB Signal Stream transfers the stored values to host memory Figure 8 6 shows an example of a buffered pulse width measurement Figure 8 6 Buffered Pulse Width Measurement Note that if you are using an external signal as the Source at least one Source pulse should ...

Страница 99: ... the counter The counter counts the number of rising or falling edges occurring on the Source input between the two active edges of the 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 Single Period Measurement With single period measurement the counter counts the number of rising or falling edg...

Страница 100: ...ure 8 8 shows an example of a buffered period measurement In this example a period is defined by two consecutive rising edges Figure 8 8 Buffered 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 This condition ensures that correct values are returned by the counter If this t0 At t0 the ...

Страница 101: ...The counter counts the number of rising or falling edges occurring on the Source input between two edges of the Gate signal You can calculate the semi period of the Gate input by multiplying the period of the 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 Buffered Semi Period...

Страница 102: ...n about connecting counter signals refer to the Default Counter Timer Pinouts section Frequency Measurement You can use the counters to measure frequency in several different ways You can choose one of the following methods depending on your application 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 fo...

Страница 103: ...ebase This method is good for low to medium frequency signals You can route the signal to measure F1 to the Gate of a counter You can route a known timebase Ft to the Source of the counter The known timebase can be 80MHzTimebase For signals that might be slower than 0 02 Hz use a slower known timebase You can configure the counter to make K 1 buffered period measurements Recall that the first peri...

Страница 104: ... for high frequency signals In this method you route a pulse of known duration T to the Gate of a counter You can generate the pulse using a second counter You also can generate the pulse externally and connect it to a PFI terminal You only need to use one counter if you generate the pulse externally Route the signal to measure F1 to the Source of the counter Configure the counter for a single pul...

Страница 105: ...quency measurement In this method you generate a long pulse using the signal to measure You then measure the long pulse with a known timebase The USB 621x device can measure this long pulse more accurately than the faster input signal You can route the signal to measure to the Source input of Counter 0 as shown in Figure 8 13 Assume this signal to measure has frequency F1 Configure Counter 0 to ge...

Страница 106: ...ulse is J F2 Therefore the frequency of F1 is given by F1 F2 N J 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 the measurement duration Method 1 uses only one counter It is a good method for many applications However the accu...

Страница 107: ... the frequency of the signal to measure decreases At very low frequencies Method 2 may be too inaccurate for your application Another disadvantage of Method 2 is that it requires two counters if you cannot provide an external signal of known width An advantage of Method 2 is that the measurement completes in a known amount of time Method 3 measures high and low frequency signals accurately However...

Страница 108: ...perform measurements of quadrature encoders that use X1 X2 or X4 encoding A quadrature encoder can have up to three channels channels A B and Z X1 Encoding When channel A leads channel B in a quadrature cycle the counter increments When channel B leads channel A in a quadrature cycle the counter decrements The amount of increments and decrements per cycle depends on the type of encoding X1 X2 or X...

Страница 109: ... as shown in Figure 8 16 Figure 8 16 X4 Encoding Channel Z Behavior Some quadrature encoders have a third channel channel Z which is also referred to as the index channel A high level on channel Z causes the counter to be reloaded with a specified value in a specified phase of the quadrature cycle You can program this reload to occur in any one of the four phases in a quadrature cycle Channel Z be...

Страница 110: ...rst The reload occurs within one maximum timebase period after the reload phase becomes true After the reload occurs the counter continues to count as before The figure illustrates channel Z reload with X4 decoding Figure 8 17 Channel Z Reload with X4 Decoding Measurements Using Two Pulse Encoders The counter supports two pulse encoders that have two channels channels A and B The counter increment...

Страница 111: ...ate input The counter stores the count in a hardware save register You can configure the rising or falling edge of the Aux input to be the active edge You can configure the rising or falling edge of the Gate input to be the active edge Use this type of measurement to count events or measure the time that occurs between edges on two signals This type of measurement is sometimes referred to as start...

Страница 112: ...active edge of the Gate signal and an active edge of the Aux signal The counter then stores the count in a hardware save register On the next active edge of the Gate signal the counter begins another measurement A USB Signal Stream transfers the stored values to host memory Figure 8 20 shows an example of a buffered two signal edge separation measurement Figure 8 20 Buffered Two Signal Edge Separa...

Страница 113: ...t rising or falling Figure 8 21 shows a generation of a pulse with a pulse delay of four and a pulse width of three using the rising edge of Source Figure 8 21 Single Pulse Generation Single Pulse Generation with Start Trigger The counter can output a single pulse in response to one pulse on a hardware Start Trigger signal The pulse appears on the Counter n Internal Output signal of the counter Yo...

Страница 114: ...ou can specify a delay from the Start Trigger to the beginning of each pulse You also can specify the pulse width The delay and pulse width are measured in terms of a number of active edges of the Source input The counter ignores the Gate input while a pulse generation is in progress After the pulse generation is finished the counter waits for another Start Trigger signal to begin another pulse ge...

Страница 115: ...unter can begin the pulse train generation as soon as the counter is armed or in response to a hardware start trigger You can route the Start Trigger to the Gate input of the counter You also can use the Gate input of the counter as a Pause Trigger if it is not used as a Start Trigger The counter pauses pulse generation when the Pause Trigger is active Figure 8 24 shows a continuous pulse train ge...

Страница 116: ...or generates the Frequency Output signal The Frequency Output signal is the Frequency Output Timebase divided by a number you select from 1 to 16 The Frequency Output Timebase can be either the 20 MHz Timebase divided by 2 or the 100 kHz Timebase The duty cycle of Frequency Output is 50 if the divider is either 1 or an even number For an odd divider suppose the divider is set to D In this case Fre...

Страница 117: ...ively increments the delay between the Gate and the pulse on the output by a specified amount Thus the delay between the Gate and the pulse produced successively increases The increase in the delay value can be between 0 and 255 For instance if you specify the increment to be 10 the delay between the active Gate edge and the pulse on the output increases by 10 every time a new pulse is generated S...

Страница 118: ...SB 621x devices feature the following counter timing signals Counter n Source Signal Counter n Gate Signal Counter n Aux Signal Counter n A Signal Counter n B Signal Counter n Z Signal Counter n Up_Down Signal Counter n HW Arm Signal Counter n Internal Output Signal Counter n TC Signal Frequency Output Signal In this section n refers to either Counter 0 or 1 For example Counter n Source refers to ...

Страница 119: ...211 6215 Devices PFI 0 3 USB 6212 6216 Devices PFI 0 15 USB 6218 Devices PFI 0 3 PFI 8 11 In addition Counter 1 TC or Counter 1 Gate can be routed to Counter 0 Source Counter 0 TC or Counter 0 Gate can be routed to Counter 1 Source 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 output PFI t...

Страница 120: ... AI Sample Clock ai SampleClock AI Convert Clock ai ConvertClock AO Sample Clock ao SampleClock In addition Counter 1 Internal Output or Counter 1 Source can be routed to Counter 0 Gate Counter 0 Internal Output or Counter 0 Source can be routed to Counter 1 Gate Some of these options may not be available in some driver software Routing Counter n Gate to an Output Terminal You can route Counter n ...

Страница 121: ...dent input selectors for each of the A B and Z inputs You can route any input PFI signal to each input Counter n Up_Down Signal Counter n Up_Down is another name for the Counter n B signal Counter n HW Arm Signal The Counter n HW Arm signal enables a counter to begin an input or output function To begin any counter input or output function you must first enable or arm the counter In some applicati...

Страница 122: ...he Counter n Internal Output signal changes in response to Counter n TC The two software selectable output options are pulse output on TC and toggle output on TC The output polarity is software selectable for both options With pulse or pulse train generation tasks the counter drives the pulse s on the Counter n Internal Output signal The Counter n Internal Output signal can be internally routed to...

Страница 123: ...gnals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information about how to connect your signals for common counter measurements and generations USB 621x default PFI lines for counter functions are listed in Physical Channels in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later Table 8 4 Default NI DAQmx Counter Timer Pins for USB 6210 6211 6215 Devices Cou...

Страница 124: ...rigger can be configured to begin a finite or continuous pulse generation Once a continuous generation has triggered the pulses continue to generate until you stop the operation in software For finite generations the specified number of pulses is generated and the generation stops unless you use the retriggerable attribute When you use this attribute subsequent start triggers cause the generation ...

Страница 125: ...riod to measure The counter begins counting rising edges of Source t2 The rising edge of Sample Clock indicates that the USB 621x device should store the result of the measurement of the current period when the period ends t3 The rising edge of Gate indicates the end of the first period The USB 621x device stores the counter value in the buffer t4 The rising edge of Gate indicates the end of the s...

Страница 126: ...lock with a 40 MHz frequency Note NI DAQmx only supports filters on counter inputs The following is an example of low to high transitions of the input signal High to low transitions work similarly Assume that an input terminal has been low for a long time The input terminal then changes from low to high but glitches several times When the filter clock has sampled the signal high on N consecutive e...

Страница 127: ... rolls over This counter can run faster than the larger counters which simply count the rollovers of this smaller counter 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 Figure 8 30 Prescaling Prescaling is intended to be used for frequency measurement where the measurement is made on a continuous repetiti...

Страница 128: ...ould store the number of times an external Source pulses between rising edges on the Gate signal Example Application That Works Correctly No Duplicate Counting Figure 8 31 shows an external buffered signal as the period measurement Source Figure 8 31 Duplicate Count Prevention Example On the first rising edge of Gate the current count of 7 is stored On the next rising edge of Gate the counter stor...

Страница 129: ...er does not write the correct data to the buffer Figure 8 32 Duplicate Count Example Example Application That Prevents Duplicate Count With duplicate count prevention the counter synchronizes both the Source and Gate signals to the 80 MHz Timebase By synchronizing to the timebase the counter detects edges on Gate even if the Source does not pulse This enables the correct current count to be stored...

Страница 130: ...nchronously to the Source signal With duplicate count prevention the counter value and 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 USB 621x devices Disabling duplicate count prevention is not supported Gate 0 7 7 6 7 0 1 Counter detects rising Gate edge Source Cou...

Страница 131: ...nd clock generation are referenced to an isolated ground as shown in Figure 9 1 Figure 9 1 USB 6215 6216 6218 Block Diagram The bus interface circuitry is referenced to a non isolated ground The following table lists the ground symbols 1 USB 6216 devices have PFI static DIO circuitry Ground Type Symbol Isolated Ground Non Isolated Ground Analog Output Digital I O Analog Input Counters PFI Digital ...

Страница 132: ...Devices section of Chapter 6 Digital I O The Connecting PFI Input Signals section of Chapter 7 PFI Digital Isolation USB 6215 6216 6218 devices use digital isolators Unlike analog isolators digital isolators do not introduce any analog error in the measurements taken by the device The A D converter used for analog input is on the isolated side of the device The analog inputs are digitized before t...

Страница 133: ...non parasitic resistances causing voltage spikes These voltage spikes are called common mode noise a noise source that travels in the ground and is therefore common to both the ground and any signal referenced to the ground such as AI AO and digital signals Common mode noise appears at the harmonics of the switching power supply frequency and can corrupt measurements depending on the system setup ...

Страница 134: ...apacitor between the isolated board ground and earth ground The voltage rating of the capacitor must be larger than the voltage drop between the isolated ground and earth ground Non Isolated Systems A non isolated measurement system is one where the device s isolated front end connects to earth ground Add an AC return path from the device isolated ground to earth ground For non isolated systems an...

Страница 135: ... User input through the PFI terminals Routes and generates the main clock signals for the USB 621x device 80 MHz Timebase The 80 MHz Timebase can be used as the Source input to the 32 bit general purpose counter timers The 80 MHz Timebase is generated from the onboard oscillator 20 MHz Timebase The 20 MHz Timebase normally generates many of the AI and AO timing signals The 20 MHz Timebase also can...

Страница 136: ... Signal Stream is available for each measurement and acquisition block Analog input Analog output Counter 0 Counter 1 Data Transfer Methods The two primary ways to transfer data across the USB bus are USB Signal Stream and programmed I O USB Signal Stream A method to transfer data between the device and computer memory using USB bulk transfers without intervention of the microcontroller on the NI ...

Страница 137: ...ion of Chapter 5 Analog Output for more information Changing Data Transfer Methods USB 621x 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 ...

Страница 138: ...ing sections The Analog Input Digital Triggering section of Chapter 4 Analog Input The Analog Output Digital Triggering section of Chapter 5 Analog Output The Counter Triggering section of Chapter 8 Counters Triggering with a Digital Source Your USB 621x device can generate a trigger on a digital signal You must specify a source and an edge The digital source can be any input PFI signal The edge c...

Страница 139: ...User Manual 12 2 ni com You also can program your USB 621x device to perform an action in response to a trigger from a digital source The action can affect the following Analog input acquisition Analog output generation Counter behavior ...

Страница 140: ...ollowing USB 621x devices USB 6210 USB 6211 6215 USB 6212 6216 Screw Terminal USB 6212 6216 Mass Termination USB 6218 Refer to the NI USB 621x Specifications available on the NI DAQ Device Documentation Browser or from ni com manuals for more detailed information about USB 621x devices To obtain documentation for devices not listed here refer to ni com manuals ...

Страница 141: ...ns section of Chapter 3 Connector and LED Information Figure A 1 USB 6210 Pinout 5 6 7 8 1 2 3 4 13 14 15 16 9 10 11 12 AI 1 AI 9 AI 2 AI 10 AI 3 AI 11 AI SENSE AI 4 AI 12 AI 5 AI 13 AI GND AI 6 AI 14 AI 7 AI 15 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 NC NC RESERVED AI 0 AI 8 21 22 23 24 17 18 19 20 29 30 3...

Страница 142: ... DAQmx Help or the LabVIEW Help in version 8 0 or later Table A 1 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 1 PFI 0 CTR 0 OUT 6 PFI 4 CTR 0 A 1 PFI 0 CTR 0 Z 3 PFI 2 CTR 0 B 2 PFI 1 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTR 1 A 4 PFI 3 CTR 1 Z 2 PFI 1 CTR 1 B 3 PFI 2 FREQ O...

Страница 143: ...gnal Descriptions section of Chapter 3 Connector and LED Information Figure A 2 USB 6211 6215 Pinout 5 6 7 8 1 2 3 4 13 14 15 16 9 10 11 12 AI 1 AI 9 AI 2 AI 10 AI 3 AI 11 AI SENSE AI 4 AI 12 AI 5 AI 13 AI GND AI 6 AI 14 AI 7 AI 15 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 AO 1 AO GND AI 0 AI 8 21 22 23 ...

Страница 144: ... DAQmx Help or the LabVIEW Help in version 8 0 or later Table A 2 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 1 PFI 0 CTR 0 OUT 6 PFI 4 CTR 0 A 1 PFI 0 CTR 0 Z 3 PFI 2 CTR 0 B 2 PFI 1 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTR 1 A 4 PFI 3 CTR 1 Z 2 PFI 1 CTR 1 B 3 PFI 2 FREQ O...

Страница 145: ...AI 5 AI 13 AI GND AI 6 AI 14 AI 7 AI 15 PFI 0 P1 0 PFI 1 P1 1 PFI 2 P1 2 PFI 3 P1 3 D GND PFI 4 P1 4 PFI 5 P1 5 PFI 6 P1 6 PFI 7 P1 7 5 V D GND AO 0 AO 1 AO GND AI 0 AI 8 5 6 7 8 1 2 3 4 13 14 15 16 9 10 11 12 21 22 23 24 17 18 19 20 29 30 31 32 25 26 27 28 D GND P0 4 P0 5 P0 6 P0 7 D GND P0 8 P0 9 P0 10 P0 11 D GND P0 12 P0 13 P0 14 P0 15 D GND PFI 8 P2 0 PFI 9 P2 1 PFI 10 P2 2 PFI 11 P2 3 D GND ...

Страница 146: ...lp or the LabVIEW Help in version 8 0 or later Table A 3 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 33 PFI 8 CTR 0 GATE 34 PFI 9 CTR 0 AUX 35 PFI 10 CTR 0 OUT 38 PFI 12 CTR 0 A 33 PFI 8 CTR 0 Z 34 PFI 9 CTR 0 B 35 PFI 10 CTR 1 SRC 4 PFI 3 CTR 1 GATE 6 PFI 4 CTR 1 AUX 36 PFI 11 CTR 1 OUT 39 PFI 13 CTR 1 A 4 PFI 3 CTR 1 Z 6 PFI 4 CTR 1 B 36 PFI 11...

Страница 147: ...6 Mass Termination USB 6212 6216 Mass Termination Pinout Figure A 4 shows the pinout of the USB 6212 Mass Termination and USB 6216 Mass Termination For a detailed description of each signal refer to the I O Connector Signal Descriptions section of Chapter 3 Connector and LED Information ...

Страница 148: ... AI GND AI 3 AI 10 AI GND AI 1 AI 8 D GND PFI 8 P2 0 PFI 7 P1 7 PFI 13 P2 5 PFI 4 P1 4 PFI 3 P1 3 PFI 2 P1 2 D GND PFI 15 P2 7 D GND PFI 10 P2 2 PFI 11 P2 3 P0 3 P0 7 P0 2 D GND P0 5 P0 0 D GND AO GND AO GND AI GND AI 7 AI 14 AI GND AI 5 AI 12 AI SENSE AI 11 AI GND AI 2 AI 9 AI GND AI 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 4...

Страница 149: ...connect your USB 6212 6216 Mass Termination device to an SCC module carrier such as the SC 2345 SC 2350 or SCC 68 use an SH68 68 EPM shielded cable The SCC carrier must be externally powered when used with a USB 6212 6216 Mass Termination device Refer to the 5 V Power section of Chapter 3 Connector and LED Information and the NI USB 621x Specifications for more information Table A 4 Default NI DAQ...

Страница 150: ...ocouple connector BNC 2090A Desktop rack mountable device with 22 BNCs for connecting analog digital and timing signals Screw Terminal Accessories National Instruments offers several styles of screw terminal connector blocks Use an SH68 68 EPM shielded cable to connect a USB 6212 6216 Mass Termination device to a connector block such as the following CB 68LP and CB 68LPR unshielded connector block...

Страница 151: ... 1000 is a configurable enclosure that gives user defined connectivity and flexibility through customized panelettes Visit ni com for more information about the CA 1000 Refer to the USB 621x Mass Termination Custom Cabling section of Chapter 2 DAQ System Overview for more information about custom cabling solutions ...

Страница 152: ... 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 AO 1 AO GND AI 0 AI 8 5 6 7 8 1 2 3 4 13 14 15 16 9 10 11 12 21 22 23 24 17 18 19 20 29 30 31 32 25 26 27 28 AI 17 AI 25 AI 18 AI 26 AI 19 AI 27 AI GND AI 20 AI 28 AI 21 AI 29 AI GND AI 22 AI 30 AI 23 AI 31 PFI 8 P0 4 In PFI 9 P0 5 In PFI 10 P0 6 In PFI 11 P0 7 In D GND PFI 12 P1 4 Out PFI 13 P1 5 ...

Страница 153: ...the LabVIEW Help in version 8 0 or later Table A 5 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 34 PFI 9 CTR 0 OUT 6 PFI 4 CTR 0 A 1 PFI 0 CTR 0 Z 2 PFI 1 CTR 0 B 34 PFI 9 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 35 PFI 10 CTR 1 OUT 7 PFI 5 CTR 1 A 4 PFI 3 CTR 1 Z 3 PFI 2 CTR 1 B 35 PFI 10 FREQ OUT 8 PFI ...

Страница 154: ...n AI 0 To circumvent this problem use a voltage follower that has operational amplifiers op amps with unity gain for each high impedance source before connecting to a USB 621x device Otherwise you must decrease the sample rate for each channel Another common cause of channel crosstalk is due to sampling among multiple channels at various gains In this situation the settling times can increase For ...

Страница 155: ...ferenced Signal Sources section of Chapter 4 Analog Input for more information How can I use the AI Sample Clock and AI Convert Clock signals on a USB 621x device to sample the AI channel s USB 621x devices use AI Sample Clock and AI Convert Clock to perform interval sampling As Figure B 1 shows AI Sample Clock controls the sample period which is determined by the following equation 1 sample perio...

Страница 156: ...tches on the output signal These glitches are normal when a DAC switches from one voltage to another it produces glitches due to released charges The largest glitches occur when the most significant bit of the 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 for more informat...

Страница 157: ...r Standard Service Program Membership This program entitles members to direct access to NI Applications Engineers via phone and email for one to one technical support as well as exclusive access to ondemand training modules via the Services Resource Center NI offers complementary membership for a full year after purchase after which you may renew to continue your benefits For information about oth...

Страница 158: ... by visiting ni com certification Calibration Certificate If your product supports calibration you can obtain the calibration certificate for your product at ni com calibration If you searched ni com and could not find the answers you need contact your local office or NI corporate headquarters Phone numbers for our worldwide offices are listed at the front of this manual You also can visit the Wor...

Страница 159: ... Glossary Symbol Prefix Value p pico 10 12 n nano 10 9 μ micro 10 6 m milli 10 3 k kilo 103 M mega 106 Symbols Percent Positive of or plus Negative of or minus Plus or minus Less than Greater than Less than or equal to Greater than or equal to Per º Degree Ω Ohm ...

Страница 160: ...that varies smoothly over a continuous range of values rather than in discrete steps analog output signal An output signal that varies smoothly over a continuous range of values rather than in discrete steps analog trigger A trigger that occurs at a user selected point on an incoming analog signal Triggering can be set to occur at a specific level on either an increasing or a decreasing signal pos...

Страница 161: ...ed bits of data an eight bit binary number Also used to denote the amount of memory required to store one byte of data block diagram A pictorial description or representation of a program or algorithm buffer 1 Temporary storage for acquired or generated data 2 A memory device that stores intermediate data between two devices bus buses The group of electrical conductors that interconnect individual...

Страница 162: ...eads to the instrument front end Common mode rejection is only a relevant specification for systems having a balanced or differential input common mode signal 1 Any voltage present at the instrumentation amplifier inputs with respect to amplifier ground 2 The signal relative to the instrument chassis or computer s ground of the signals from a differential input This is often a noise signal such as...

Страница 163: ...O For programmed I O transfers the CPU in the PC reads data from the DAQ device whenever the CPU receives a software signal to acquire a single data point Interrupt based data transfers occur when the DAQ device sends an interrupt to the CPU telling the CPU to read the acquired data from the DAQ device DMA transfers use a DMA controller instead of the CPU to move acquired data from the device into...

Страница 164: ...information by a set of discrete values according to a prescribed law These values are represented by numbers digital trigger A TTL level signal having two discrete levels A high and a low level DIO Digital input output DMA Direct Memory Access A method by which data can be transferred to from computer memory from to a device or memory on the bus while the processor does something else DMA is the ...

Страница 165: ... a process that requires the servicing of interrupts and often the programming of the DMA controller This process can take several milliseconds in some cases During this time data accumulates in the FIFO for future retrieval With a larger FIFO longer latencies can be tolerated In the case of analog output a FIFO permits faster update rates because the waveform data can be stored on the FIFO ahead ...

Страница 166: ...nd or output parameters and returns a value when executed G glitch An unwanted signal excursion of short duration that is usually unavoidable GND See ground ground 1 A pin 2 An electrically neutral wire that has the same potential as the surrounding earth Normally a noncurrent carrying circuit intended for safety 3 A common reference point for an electrical system H hardware The physical component...

Страница 167: ...oltages at its two inputs An instrumentation amplifier normally has high impedance differential inputs and high common mode rejection interchannel delay Amount of time that passes between sampling consecutive channels in an AI scan list The interchannel delay must be short enough to allow sampling of all the channels in the channel list within the sample interval The greater the interchannel delay...

Страница 168: ...uisition products that have multiple analog input channels digital I O channels timing and optionally analog output channels 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 module A board assembly and its associated mechanical parts front panel optional shields and so on A module contains everyt...

Страница 169: ... and Measurement Studio increased performance such as faster single point analog I O and a simpler API for creating DAQ applications using fewer functions and VIs than earlier versions of NI DAQ NI PGIA See instrumentation amplifier non referenced signal sources Signal sources with voltage signals that are not connected to an absolute reference or system ground Also called floating signal sources ...

Страница 170: ... width The time from the rising to the falling slope of a pulse at 50 amplitude Q quadrature encoder An encoding technique for a rotating device where two tracks of information are placed on the device with the signals on the tracks offset by 90 from each other This makes it possible to detect the direction of the motion R range The maximum and minimum parameters between which a sensor instrument ...

Страница 171: ...ntrols how often a scan is initialized is regulated by the AI Sample Clock signal scan rate Reciprocal of the scan interval sensor A device that responds to a physical stimulus heat light sound pressure motion flow and so on and produces a corresponding electrical signal Primary characteristics of sensors are sensitivity frequency range and linearity signal conditioning 1 Electronic equipment that...

Страница 172: ...ity of current sources higher is better synchronous 1 Hardware A property of an event that is synchronized to a reference clock 2 Software A property of a function that begins an operation and returns only when the operation is complete A synchronous process is therefore locked and no other processes can run during this time T task In NI DAQmx a collection of one or more channels timing and trigge...

Страница 173: ...mand The trigger may also be derived from attributes of the actual signal to be acquired such as the level and slope of the signal tsc Source clock period tsp Source pulse width TTL Transistor Transistor Logic A digital circuit composed of bipolar transistors wired in a certain manner A typical medium speed digital technology Nominal TTL logic levels are 0 and 5 V U USB Universal Serial Bus A 480 ...

Страница 174: ...age VOH Volts output high VOL Volts output low Vout Volts out Vs Signal source voltage virtual channel See channel W 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 ...

Страница 175: ...ock 4 16 ai ConvertClockTimebase 4 19 ai HoldCompleteEvent 4 19 ai PauseTrigger 4 22 ai ReferenceTrigger 4 21 ai SampleClock 4 14 ai SampleClockTimebase 4 15 ai StartTrigger 4 20 analog input 4 1 channels sampling with AI Sample Clock and AI Convert Clock B 2 charge injection B 1 circuitry 4 1 connecting signals on USB 6210 6211 6212 devices 4 23 connecting signals on USB 6215 6216 6218 devices 4 ...

Страница 176: ...plications counter input 8 2 counter output 8 20 edge counting 8 2 applying rubber feet 1 4 arm start trigger 8 31 B board mounting 1 5 buffered edge counting 8 3 hardware timed acquisitions 4 9 hardware timed generations 5 3 period measurement 8 7 pulse width measurement 8 5 semi period measurement 8 8 two signal edge separation measurement 8 19 bus interface 11 1 C cables 2 4 custom 2 4 USB 6212...

Страница 177: ... controlling counting direction 8 2 conventions used in the manual xiii counter input and output 8 30 Counter n A signal 8 28 Counter n Aux signal 8 27 Counter n B signal 8 28 Counter n Gate signal 8 27 Counter n HW Arm signal 8 28 Counter n Internal Output signal 8 29 Counter n Source signal 8 26 Counter n TC signal 8 29 Counter n Up_Down signal 8 28 Counter n Z signal 8 28 counter signals Counte...

Страница 178: ...alog input troubleshooting B 1 differential connections using with floating signal sources 4 27 using with ground referenced signal sources 4 33 when to use with floating signal sources 4 25 when to use with ground referenced signal sources 4 32 digital isolation 9 2 isolators 9 1 routing 10 1 signals connecting USB 6210 6211 6215 6218 6 3 source triggering 12 1 digital I O triggering 12 1 USB 621...

Страница 179: ...scription 4 25 using in differential mode 4 27 using in NRSE mode 4 30 using in RSE mode 4 31 when to use in differential mode 4 25 when to use in NRSE mode 4 26 when to use in RSE mode 4 25 FREQ OUT signal 8 29 frequency division 8 24 generation 8 23 generator 8 23 measurement 8 9 Frequency Output signal 8 29 fuse replacement USB devices 3 3 G generations analog output data 5 2 buffered hardware ...

Страница 180: ...ces C 1 instrumentation amplifier 4 1 interface bus 11 1 isolated DAQ devices 9 1 benefits 9 2 common mode noise 9 3 isolation barrier 4 2 5 2 isolators 9 1 K KnowledgeBase C 1 L LabVIEW documentation xv LabVIEW PDA 8 x xiv LabWindows CVI documentation xvi LED 3 5 Linux xiv low impedance sources 4 6 M Mac OS X xiv Measurement Studio documentation xvi measurements buffered period 8 7 buffered pulse...

Страница 181: ...round referenced signal sources 4 32 NRSE connections using with floating signal sources 4 30 using with ground referenced signal sources 4 34 when to use with floating signal sources 4 26 when to use with ground referenced signal sources 4 32 O on demand acquisitions 4 8 edge counting 8 2 timing 4 8 order of channels for scanning 4 6 other software 1 1 output signal glitches B 3 minimizing glitch...

Страница 182: ...h ground referenced signal sources 4 33 related documentation xiv retriggerable single pulse generation 8 21 routing digital 10 1 RSE configuration 4 31 RSE connections using with floating signal sources 4 31 when to use with floating signal sources 4 25 when to use with ground referenced signal sources 4 33 rubber feet 1 4 S sample clock 8 32 edge counting 8 3 scan speed 4 8 scanning speed 4 8 se...

Страница 183: ... 2 simple pulse generation 8 20 single period measurement 8 6 point edge counting 8 2 pulse generation 8 20 retriggerable 8 21 with start trigger 8 20 pulse width measurement 8 4 semi period measurement 8 8 two signal edge separation measurement 8 18 single ended connections for floating signal sources 4 31 RSE configuration 4 31 software configuring AI ground reference settings 4 5 NI resources C...

Страница 184: ...211 A 4 analog input signals 4 23 default counter timer pins A 5 digital I O 6 1 pinout A 4 USB 6212 Mass Termination A 8 accessories A 10 analog input signals 4 23 cables A 10 default counter timer pins A 10 digital I O 6 4 pinout A 8 USB 6212 Screw Terminal A 6 analog input signals 4 23 default counter timer pins A 7 digital I O 6 4 pinout A 6 USB 6215 A 4 analog input signals 4 36 default count...

Страница 185: ...cking 1 4 USB cable strain relief 1 3 USB 621x Screw Terminal signal labels 1 2 using low impedance sources 4 6 using PFI terminals as static digital I Os 7 3 as timing input signals 7 2 to export timing output signals 7 3 using short high quality cabling 4 6 W waveform generation signals 5 4 Web resources C 1 X X1 encoding 8 15 X2 encoding 8 16 X4 encoding 8 16 ...

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