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Chapter 3

Device Overview and Theory of Operation

National Instruments Corporation

3-13

In high-hysteresis triggering mode, shown in Figure 3-11, the trigger is
generated when the signal value is greater than

highValue

, with the

hysteresis specified by

lowValue

Figure 3-11.

High-Hysteresis Triggering Mode

In low-hysteresis triggering mode, shown in Figure 3-12, the trigger is
generated when the signal value is less than

lowValue

, with the hysteresis

specified by

highValue

Figure 3-12.

Low-Hysteresis Triggering Mode

You can use the

EXT TRIG

SMB connector on the NI 447

for dedicated

external digital triggering.

Alternately, you can trigger the NI 447

from any other NI device that has

the RTSI bus feature. You can programmatically route any RTSI/TRIG line
to the NI 447

except RTSI 5/TRIG 5, which is reserved for internal use

when synchronizing multiple NI 447

devices.

Note

A PXI chassis with multiple PXI buses might not have RTSI connections across the

bus boundaries.

highValue

Trigger

lowValue

highValue

Trigger

lowValue

Содержание NI 447 Series

Страница 1: ...DAQ NI 447X User Manual Dynamic Signal Acquisition Devices for PCI and PXI CompactPCI NI 447X User Manual April 2003 Edition Part Number 322940C 01...

Страница 2: ...ermany 49 0 89 741 31 30 Greece 30 2 10 42 96 427 Hong Kong 2645 3186 India 91 80 4190000 Israel 972 0 3 6393737 Italy 39 02 413091 Japan 81 3 5472 2970 Korea 82 02 3451 3400 Malaysia 603 9059 6711 Me...

Страница 3: ...e failures caused by owner s failure to follow the National Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts an...

Страница 4: ...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 d...

Страница 5: ...t denotes items that you must select or click in the software such as menu items and dialog box options Bold text also denotes parameter names and hardware labels CompactPCI A Eurocard configuration o...

Страница 6: ...d PCI A high performance expansion bus architecture originally developed by Intel to replace ISA and EISA it is now accepted as a standard for PCs and workstations and offers a theoretical maximum tra...

Страница 7: ...2 1 Testing the Device 2 3 Connecting Signals 2 4 Signal Sources 2 7 Floating Signal Sources 2 8 Grounded Signal Sources 2 8 Generating Onboard Current Excitation with IEPE Circuitry 2 9 Input Coupli...

Страница 8: ...a ADCs and the Oversample Clock 3 14 The NI 447X SYNC Pulse 3 15 The Acquisition Start Trigger 3 17 Chapter 4 Calibration Loading Calibration Constants 4 1 Self Calibration 4 1 External Calibration 4...

Страница 9: ...switchable 4 mA current source for integrated circuit piezoelectric also known as Integral Electronic Piezoelectric IEPE accelerometers and microphone preamplifiers The NI PXI 4472B differs from the...

Страница 10: ...Visual C NI DAQ driver software and documentation A PCI bus computer or a PXI or CompactPCI chassis and controller Female SMB connector cables Related Documentation The following documents contain inf...

Страница 11: ...ify NI if the device appears damaged in any way Do not install a damaged device into the computer Store the NI 447X device in the antistatic envelope when not in use Software Programming Choices When...

Страница 12: ...ng LabVIEW with National Instruments DAQ hardware is included with LabVIEW LabWindows CVI is a complete ANSI C ADE that features an interactive user interface code generation tools and the LabWindows...

Страница 13: ...PXI chassis but not in a CompactPCI chassis Note The CompactPCI specification does not require the chassis to supply 3 3 V to the device but the NI PXI 4472 requires 3 3 V power on the PCI bus in ord...

Страница 14: ...ocument Use the NI 447X only with the chassis modules accessories and cables specified in the installation instructions You must have all covers and filler panels installed during operation of the NI...

Страница 15: ...stablish standard impulse withstand voltage levels that commonly occur in electrical distribution systems The following is a description of installation categories Installation Category I is for measu...

Страница 16: ...nstallations distribution boards and circuit breakers Other examples are wiring including cables bus bars junction boxes switches socket outlets in the fixed installation and stationary motors with pe...

Страница 17: ...is important to install the NI DAQ before installing the NI 447X device to ensure that the device is properly detected Installing the Hardware You can install the NI 447X device in any available slot...

Страница 18: ...nd is fully inserted into the slot 9 Replace the cover 10 Plug in and power on the computer Note For proper cooling all covers and filler panels must be installed The NI PCI 4472 or NI PCI 4474 is now...

Страница 19: ...insert the device into the chassis 7 Screw the front panel of the NI PXI 4472 to the front panel mounting rail of the system Note To ensure a good ground connection securely fasten the front panel of...

Страница 20: ...472 and four male SMB connectors on the front panel of the NI PCI 4474 for connecting analog signals Each NI 447X device also has one male SMB connector for connecting a digital trigger The analog inp...

Страница 21: ...ation 2 5 NI 447X User Manual Figure 2 1 NI PCI PXI 4472 Front Panels NI PXI 4472B EXT TRIG CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 NI PXI 4472B NI PXI 4472 EXT TRIG CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 NI PXI 447...

Страница 22: ...t Panel Before configuring the AI channels and making signal connections you must determine the following Whether the input signal source is floating or grounded Whether the accelerometer or microphon...

Страница 23: ...The voltage range of the input signal Signal Sources The AI channels of the NI 447X have unbalanced differential inputs Figure 2 3 shows the input configurations for floating and grounded signal sourc...

Страница 24: ...47X If you are using an NI PXI 4472 be sure to tighten the small screws at the top and bottom of the front face of the module Grounded Signal Sources A ground referenced signal source connects in some...

Страница 25: ...excitation only for the channels that are configured for an acquisition in AI Config vi If you are programming in the NI DAQ text application program interface API you should use the AI_Change_Paramet...

Страница 26: ...ut gain the component count in the input signal path is reduced resulting in less noise and distortion If the input signal has an amplitude greater than 10 V it is clipped and introduces large errors...

Страница 27: ...wing recommendations apply mainly to AI signal routing to the NI 447X although they also apply to signal routing in general Minimize noise pickup and maximize measurement accuracy by taking the follow...

Страница 28: ...s Although the software allows you to use a lower sample rate you must always use a sample rate of at least 1 0 kS s to ensure the accuracy of the data acquisition Synchronizing Multiple Devices This...

Страница 29: ...le for the version of NI DAQ you are using NI PXI 4472 To synchronize two or more NI PXI 4472 devices in a PXI CompactPCI system one of the NI PXI 4472 devices must be located in PXI Slot 2 This devic...

Страница 30: ...NI 447X If you suspect the filters are not passing your test signal simply increase the sampling rate or decrease the analog signal frequency until the sampling rate is more than twice the analog fre...

Страница 31: ...and other useful information for understanding how the device works Functional Overview Figure 3 1 shows a block diagram of the digital functions and the analog function block diagram is shown in Figu...

Страница 32: ...r The EXT TRIG line is compatible with 5V TTL and CMOS voltage levels CH 0 n are AI channels 0 through n Input impedance on the positive signal wire of each input channel is 1 M in parallel with 60 pF...

Страница 33: ...stage and their returns are routed to AIGND through a common mode choke The NI 447X ADCs measure these signals when they perform A D conversions These input channels have 24 bit resolution and are si...

Страница 34: ...y components Many digitizers including the successive approximation register SAR ADCs often used in DAQ products do not have alias protection Consider an ADC running at a sampling rate of 1 000 S s In...

Страница 35: ...l components above the Nyquist frequency either before or during the digitization process can guarantee that the digitized data set is free of all aliases The NI 447X employs both digital and analog l...

Страница 36: ...t Frequency Response Figure 3 5 Input Frequency Response Near the Cutoff Amplitude dB Frequency Sample Rate fs 0 00 20 00 40 00 60 00 80 00 100 00 120 00 0 00 0 20 0 40 0 60 0 80 1 00 Amplitude dB Fre...

Страница 37: ...of the NI 447X The high cutoff frequency of the filter guarantees extremely flat amplitude response and minimal phase error for signals of interest Frequency components that could pass the digital fil...

Страница 38: ...ata to have high frequency energy This energy is spread throughout the frequency spectrum and because the clipping happens after the antialiasing filters the energy is aliased back into the baseband T...

Страница 39: ...verload detection circuitry to monitor for an overload condition If an overload is detected the data acquired at that time may be corrupt The ADC The NI 447X ADC uses a method of A D conversion known...

Страница 40: ...these factors is noise picked up from nearby electronic devices The NI 447X works best when it is kept as far away as possible from other plug in devices power supplies disk drives and computer monito...

Страница 41: ...in your system The nature of delta sigma converters means that the triggering circuits operate on the digital output of the converter Since the trigger is generated at the output of the converter trig...

Страница 42: ...el Triggering Mode In above high level triggering mode shown in Figure 3 9 the trigger is generated when the signal value is greater than highValue lowValue is unused Figure 3 9 Above High Level Trigg...

Страница 43: ...ue is less than lowValue with the hysteresis specified by highValue Figure 3 12 Low Hysteresis Triggering Mode You can use the EXT TRIG SMB connector on the NI 447X for dedicated external digital trig...

Страница 44: ...exactly equal to the frequency of the sample clock For example a 10 kHz sample clock produces a 10 kS s acquisition rate One distinguishing feature of delta sigma converters including those on the NI...

Страница 45: ...13 1 MHz The ADCs on the NI 447X operate at half the oversample clock Most delta sigma converters including those on the NI 447X require a very steady frequency for the oversample clock The DDS chip...

Страница 46: ...o the clock delay issue is to configure the master device to issue a SYNC pulse before the acquisition The clock master sends a single active low or inverted pulse on the RTSI 5 TRIG 5 line the dedica...

Страница 47: ...he SYNC pulse is automatically handled by NI DAQ through the RTSI 5 TRIG 5 line Therefore you do not need to make an explicit software call to generate or route the SYNC pulse The Acquisition Start Tr...

Страница 48: ...curate whereas the last level is the slowest most complex and most accurate Loading Calibration Constants The NI 447X is factory calibrated at approximately 25 C to the levels indicated in Appendix A...

Страница 49: ...sufficient External Calibration The onboard calibration reference voltage is stable enough for most applications but if you are using the device at an extreme temperature or if the onboard reference h...

Страница 50: ...d the NI 447X back to NI NI sends the device back to you with a new calibration certificate Please check with NI for additional information such as cost and delivery times If your company has a metrol...

Страница 51: ...forced air cooling Analog Input Channel Characteristics Number of channels NI PCI PXI 4472 4472B 8 simultaneously sampled NI PCI 4474 4 simultaneously sampled Input configuration Unbalanced differenti...

Страница 52: ...ld 50 in parallel with 0 02 F Flatness relative to 1 kHz 0 1 dB DC to 0 4535 fs max DC coupled 3 dB bandwidth 0 4863 fs Input coupling AC or DC software selectable AC 3 dB cutoff frequency NI 447X 3 4...

Страница 53: ...5 00 106 00 107 00 108 00 109 00 110 00 111 00 112 00 113 00 114 00 1 0 10 0 100 0 1000 0 Noise dB Full Scale Sample Rate kS s NOTE The change in the noise level at 51 2 kS s is due to the reduction o...

Страница 54: ...C 0 Hz to 0 4535 fs Stop band 0 5465 fs Alias rejection 110 dB Delay through ADC anti aliasing filter 38 8 sample periods Spurious free dynamic range 130 dB 1 0 kS s fs 51 2 kS s 118 dB 51 2 kS s fs 1...

Страница 55: ...s THD 0 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 160 0 0 2500 5000 7500 10000 12500 15000 17500 20000 22500 25597 Typical 60 dB FFT 10 averages 16 384 points 51 2 kS s dB Full Scale Frequency Hz 0 0 2...

Страница 56: ...B Other channel combinations Shorted input 100 dB 1 k load 90 dB Phase linearity 0 5 Interchannel phase mismatch fin in kHz 0 018 0 082 Interchannel gain mismatch 0 1dB Onboard Calibration Reference D...

Страница 57: ...ive or negative software selectable Resolution 24 bits nominal Hysteresis Programmable Digital Trigger Compatibility TTL CMOS Response Rising or falling edge Pulse width 10 ns min Bus Interface Type M...

Страница 58: ...t corrections Interval Whenever temperature is different from temperature at last internal calibration by more than 5 C External Internal voltage reference read and stored in non volatile memory Inter...

Страница 59: ...EMI CE C Tick and FCC Part 15 Class A Compliant Note For EMC compliance you must operate this device with shielded cabling CE Compliance The NI 447X devices meet the essential requirements of applicab...

Страница 60: ...rement glossary and so on Assisted Support Options Contact NI engineers and other measurement and automation professionals by visiting ni com support Our online system helps you define your question a...

Страница 61: ...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 thi...

Страница 62: ...co 10 12 n nano 10 9 micro 10 6 m milli 10 3 k kilo 103 M mega 106 G giga 109 Numbers Symbols degree ohm percent positive of or plus negative of or minus per A A amperes A D analog to digital AC alter...

Страница 63: ...cy in the resulting digitized signal and reduces noise amplitude flatness a measure of how close to constant the gain of a circuit remains over a range of frequencies API application program interface...

Страница 64: ...eject interference from a common mode signal usually expressed in decibels dB code width the smallest detectable change in an input voltage of a DAQ device common mode range the input range over which...

Страница 65: ...cases the default input of a control is a certain value often 0 that means use the current default setting For example the default input for a parameter may be do not change current setting and the de...

Страница 66: ...t case deviation of code widths from their ideal value of 1 LSB DoC Declaration of Conformity DOC the Canadian Department of Communications down counter performing frequency division on an internal si...

Страница 67: ...utput a FIFO permits faster update rates because the waveform data can be stored on the FIFO ahead of time This again reduces the effect of latencies associated with getting the data from system memor...

Страница 68: ...volving communications channels operator interface devices and or data acquisition and control interfaces IEPE Integral Electronics Piezoelectric also known as integrated circuit piezoelectric a type...

Страница 69: ...t modules that make use of these functions nidaqmsc lib is a library that contains NI DAQ functions The NI DAQ function set is broken down into object modules so that only the object modules that are...

Страница 70: ...ermocouples Nyquist frequency a frequency that is one half the sampling rate See also Nyquist Sampling Theorem Nyquist Sampling Theorem the theorem states that if a continuous bandwidth limited analog...

Страница 71: ...onfigure resources on the devices also called switchless devices port a communications connection on a computer or a remote controller posttriggering the technique used on a DAQ device to acquire a pr...

Страница 72: ...re of the instantaneous signal amplitude a measure of signal amplitude RSE See SE RTSI bus real time system integration bus the NI timing bus that connects DAQ devices directly by means of connectors...

Страница 73: ...that do not require dip switches or jumpers to configure resources on the devices also called Plug and Play devices synchronous 1 hardware a property of an event that is synchronized to a reference c...

Страница 74: ...ow 1 V a logic low and a signal above 2 4 V a logic high two s complement format a system for digitally encoding sound that stores the amplitude values as a signed number with silence represented by a...

Страница 75: ...lements typically used with a PC that has the functionality of a classic stand alone instrument 2 a LabVIEW software module VI which consists of a front panel user interface and a block diagram progra...

Страница 76: ...A 1 dynamic characteristics A 4 spurious free dynamic range figures A 5 transfer characteristics A 2 antialias filtering alias rejection at oversample rate figure 3 8 comparison of clipped signal to p...

Страница 77: ...instrument B 1 software B 1 E electromagnetic compatibility specifications A 9 environmental specifications A 8 example code B 1 excitation of current generating 2 9 EXT TRIG connector 2 10 3 2 extern...

Страница 78: ...on 2 1 NI DAQ driver software 1 3 overview 1 1 requirements for getting started 1 2 safety information 1 6 software installation 2 1 software programming choices National Instruments application softw...

Страница 79: ...xceeding rated input voltages note 2 10 front panel figure 2 5 2 6 I O connectors 3 2 input coupling 2 9 input polarity 2 10 input range 2 10 minimizing noise note 2 4 signal sources floating signal s...

Страница 80: ...tion block diagram 3 2 digital function block diagram 3 1 I O connectors 3 2 triggers 3 11 above high level triggering mode figure 3 12 below low level triggering mode figure 3 12 high hysteresis trig...

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