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Chapter 3

Device Overview and Theory of Operation

NI 4472 User Manual

3-2

ni.com

Figure 3-2.

Analog Function Block Diagram

I/O Connectors

Caution

Connections that exceed any of the maximum ratings for input signals on

the NI 4472 can damage the device, the computer, and the associated accessories.
National Instruments is

not

liable for any damage resulting from such signal connections.

The front panel of the NI 4472 has nine SMB male connectors for attaching
signal inputs.

The EXT TRIG connector is the input for the PFI0/EXT_TRIG signal.
Triggers cannot be output from the EXT TRIG connector. The EXT TRIG
line is compatible with TTL and CMOS voltage levels.

CH<0..7> are analog input channels 0 through 7. Input impedance on the
positive (signal) wire of each input channel is 1 M

Ω

in parallel with 60 pF

to ground. Input impedance on the negative (shield) wire is 50

Ω

in parallel

with 0.02 µF to ground. The signal line of each analog input channel circuit

From DDS

Serial/IO

Parallel

INPUT/CAL

MUX

AC/DC

Coupling

LP Filter

Hardware Linear

Correction

ADC0

To

FIFO

Serial/IO

Parallel

INPUT/CAL

MUX

AC/DC

Coupling

LP Filter

Hardware Linear

Correction

ADC1

To

FIFO

Serial/IO

Parallel

INPUT/CAL

MUX

AC/DC

Coupling

LP Filter

Hardware Linear

Correction

ADC7

To

FIFO

Correction

Control

Trigger

Control

Digital

Overrange

INPUT/CAL

MUX Control

Coupling

Control

EXT Digital Trigger

CH7

CH1

CH0

To

CH<0..6>

To

CH<0..6>

To

CH<0..6>

To

CH<0..6>

Содержание NI 4472

Страница 1: ...DAQ NI 4472 User Manual Dynamic Signal Acquisition Device for PCI and PXI CompactPCI NI 4472 User Manual May 2001 Edition Part Number 322940B 01...

Страница 2: ...26 00 Finland 09 725 725 11 France 01 48 14 24 24 Germany 089 741 31 30 Greece 30 1 42 96 427 Hong Kong 2645 3186 India 91805275406 Israel 03 6120092 Italy 02 413091 Japan 03 5472 2970 Korea 02 596 74...

Страница 3: ...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 and power failure or surges...

Страница 4: ...ents 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 Cla...

Страница 5: ...ought for OEMs if also available from an original manufacturer that also markets in the EU or where compliance is not required as for electrically benign apparatus or cables To obtain the DoC for this...

Страница 6: ...of precautions to take to avoid injury data loss or a system crash bold Bold text denotes items that you must select or click on in the software such as menu items and dialog box options Bold text al...

Страница 7: ...esting Your Device 2 3 Connecting Signals 2 4 Signal Sources 2 6 Floating Signal Sources 2 7 Grounded Signal Sources 2 7 Generating Onboard Current Excitation with ICP Circuitry 2 8 Input Coupling 2 8...

Страница 8: ...ise 3 10 Trigger 3 11 Device and Clocks 3 14 Chapter 4 Calibration Loading Calibration Constants 4 1 Self Calibration 4 2 External Calibration 4 2 Traceable Recalibration 4 3 Appendix A Specifications...

Страница 9: ...iggering Each input channel has an independent software switchable 4 mA current source for Integrated Circuit Piezoelectric ICP type accelerometers and microphone preamplifiers See Appendix A Specific...

Страница 10: ...n development environment such as Visual C NI DAQ for PC Compatibles and documentation Your PCI bus computer or PXI or CompactPCI chassis and controller Female SMB connector cables The following docum...

Страница 11: ...use Software Programming Choices When programming your National Instruments DAQ hardware you can use National Instruments application development environment ADE software or other ADEs In either case...

Страница 12: ...tware greatly reduces the development time for your data acquisition and control application NI DAQ NI DAQ which shipped with your NI 4472 device has an extensive library of functions that you can cal...

Страница 13: ...in device in a standard CompactPCI chassis you will be unable to use PXI specific functions but you can still use the basic plug in device functions For example the RTSI bus on your NI 4472 for PXI C...

Страница 14: ...e CompactPCI bus Table 1 1 lists the J2 pins used by your NI 4472 for PXI CompactPCI Your PXI device is compatible with any CompactPCI chassis with a sub bus that does not drive these lines Even if th...

Страница 15: ...ocument Misuse of this equipment could result in a shock hazard Do not substitute parts or modify equipment Because of the danger of introducing additional hazards do not install unauthorized parts or...

Страница 16: ...ore installing your NI 4472 device to ensure that the device is properly detected Installing Your Hardware You can install the NI 4472 device in any available slot in your PCI bus computer or PXI Comp...

Страница 17: ...ust be installed in slot 2 Refer to the Synchronizing Multiple Devices section of this chapter for more information 2 Choose an unused PXI or CompactPCI slot in your system Note For maximum performanc...

Страница 18: ...ify the installation Make sure the device is not touching other devices or components and is fully inserted in the slot 9 Plug in and turn on your computer The NI 4472 for PXI CompactPCI is now instal...

Страница 19: ...le SMB connector for connecting a digital trigger The analog inputs are unbalanced differential channels with individually configurable AC DC coupling and ICP type current conditioning The digital inp...

Страница 20: ...National Instruments Corporation 2 5 NI 4472 User Manual Figure 2 1 NI 4472 Front Panels NI 4472 FOR PXI EXT TRIG CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 NI 4472 for PXI CompactPCI NI 4472 for PCI CH0 CH1 CH2...

Страница 21: ...l Signal Sources The analog input channels of the NI 4472 have unbalanced differential inputs Figure 2 2 shows the input configurations for floating and grounded signal sources Figure 2 2 Input Config...

Страница 22: ...wo screws attached for that purpose NI 4472 for PXI CompactPCI Grounded Signal Sources A ground referenced signal source connects in some way to the building system ground and is therefore already con...

Страница 23: ...Parameter vi to control the onboard excitation You can control onboard excitation only for the channels that are configured for an acquisition in AI Config vi If you are programming in the NI DAQ text...

Страница 24: ...ositive signal line The shield does not have overvoltage protection Do not make a non ground connection to the shield Also do not connect the shield to a ground that varies more than 2 5 V from the gr...

Страница 25: ...mainly to analog input signal routing to the NI 4472 although they also apply to signal routing in general Minimize noise pickup and maximize measurement accuracy by taking the following precautions...

Страница 26: ...a sample rate of at least 1 0 kS s to ensure the accuracy of your data acquisition Synchronizing Multiple Devices The NI 4472 can send or receive the DDS clock signal and the synchronization start si...

Страница 27: ...ect_Signal in NI DAQ Function Reference Help Start Programs National Instruments DAQ NI DAQ Help Device Configuration Issues Selecting a sample rate that is less than two times the frequency of a band...

Страница 28: ...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 29: ...ine is compatible with TTL and CMOS voltage levels CH 0 7 are analog input channels 0 through 7 Input impedance on the positive signal wire of each input channel is 1 M in parallel with 60 pF to groun...

Страница 30: ...h input impedance to the analog input signals connected to your NI 4472 Signals are routed to the positive inputs of the analog input stage and their returns are routed to AIGND through a common mode...

Страница 31: ...d the Nyquist frequency the sampler cannot distinguish these parts of the signal from some signals with frequency components less than the Nyquist frequency For example suppose a sampler such as an AD...

Страница 32: ...4472 the analog sampler operates at 64 times the selected sample rate for rates above 51 2 kS s and at 128 times the selected sample rate for rates at and below 51 2 kS s For example if you select a...

Страница 33: ...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 34: ...ased into the passband region of the digital filter and is not attenuated The purpose of the analog filter is to remove these higher frequency components near multiples of the oversampling rate before...

Страница 35: ...l data 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 baseban...

Страница 36: ...as delta sigma modulation If the data rate is 51 2 kS s each ADC actually samples its input signal at 6 5536 MS s 128 times the data rate and produces 1 bit samples that are applied to the digital fil...

Страница 37: ...codes 8 388 607 and 8 388 608 Such a sine wave has an RMS magnitude of 8 388 608 1 414 5 932 537 482 least significant bits LSBs Several factors can degrade the noise performance of the inputs One of...

Страница 38: ...al crosses a specific threshold Due to the nature of delta sigma converters the triggering circuits operate on the digital output of the converter Since the trigger is generated at the output of the c...

Страница 39: ...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 40: ...than lowValue with the hysteresis specified by highValue Figure 3 12 Low Hysteresis Triggering Mode You can use the EXT TRIG input SMB connector on the NI 4472 for dedicated external digital triggeri...

Страница 41: ...rogram to receive this timebase signal The default configuration at startup is to use the internal timebase without driving the PXI backplane timebase signal This timebase is software selectable NI 44...

Страница 42: ...g applications If you do not calibrate your device your signals and measurements could have very large offset and gain errors The four levels of calibration available are described in this chapter The...

Страница 43: ...or due to time or temperature drift of the onboard voltage reference This error is addressed by external calibration which is discussed in the External Calibration section If you are interested primar...

Страница 44: ...ire factory recalibration send your NI 4472 back to National Instruments National Instruments will send the device back to you with a new calibration certificate Please check with National Instruments...

Страница 45: ...assis or computer to maintain forced air cooling Analog Input Channel Characteristics Number of channels 8 simultaneously sampled Input configuration Unbalanced differential Resolution 24 bits nominal...

Страница 46: ...n parallel with 60 pF Negative input shield 50 in parallel with 0 02 F Flatness relative to 1 kHz 0 03 dB DC to 0 4535 fs max DC coupled 3 dB bandwidth 0 4863 fs Input coupling AC or DC software selec...

Страница 47: ...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 48: ...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 49: ...kS s 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 20...

Страница 50: ...dB 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...

Страница 51: ...ware 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 Master slave Power Re...

Страница 52: ...ale Digital trigger connector SMB male Environmental Operating temperature 0 to 50 C Storage temperature 20 to 70 C Humidity 10 to 90 RH non condensing Calibration Internal On software command compute...

Страница 53: ...e you must operate this device with shielded cabling In addition all covers and filler panels must be installed See the Declaration of Conformity DoC for this product for any additional regulatory com...

Страница 54: ...e latest example programs system configurators tutorials technical news as well as a community of developers ready to share their own techniques Customer Education National Instruments provides a numb...

Страница 55: ...tes from the Worldwide Offices section of ni com Branch office Web sites provide up to date contact information support phone numbers e mail addresses and current events If you have searched the techn...

Страница 56: ...ga 106 Numbers Symbols degree ohm percent positive of or plus negative of or minus per A A amperes A D analog to digital AC alternating current AC coupled allowing the transmission of AC signals while...

Страница 57: ...latness a measure of how close to constant the gain of a circuit remains over a range of frequencies API application program interface asynchronous 1 hardware a property of an event that occurs at an...

Страница 58: ...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 59: ...t means use the current default setting For example the default input for a parameter may be do not change current setting and the default setting may be no AMUX 64T devices If you do change the value...

Страница 60: ...ferential nonlinearity a measure in LSBs of the worst case deviation of code widths from their ideal value of 1 LSB down counter performing frequency division on an internal signal drivers software th...

Страница 61: ...e case of analog output 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...

Страница 62: ...I I O input output the transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces IMD intermodulation distor...

Страница 63: ...roken down into object modules so that only the object modules that are relevant to your application are linked in while those object modules that are not relevant are not linked linearity the adheren...

Страница 64: ...ts higher than half the frequency at which it is sampled then the original signal can be recovered without distortion O offset binary format a method of digitally encoding sound that represents the ra...

Страница 65: ...g an analog value due to the finite resolution of the conversion process quantizer a device that maps a variable from a continuous distribution to a discrete distribution R relative accuracy a measure...

Страница 66: ...ibe an analog input that is measured with respect to a common ground self calibrating a property of a DSA device that has an extremely stable onboard reference and calibrates its own A D and D A circu...

Страница 67: ...nsor transfer rate the rate measured in bytes s at which data is moved from source to destination after software initialization and set up operations the maximum rate at which the hardware can operate...

Страница 68: ...sampling at a rate lower than the Nyquist frequency can cause aliasing V V volts Vcc collector common voltage power supply voltage VDC volts direct current VI virtual instrument 1 a combination of har...

Страница 69: ...to A 6 spurious free dynamic range figures A 5 transfer characteristics A 2 antialias filtering 3 4 to 3 9 alias rejection at oversample rate figure 3 8 comparison of clipped signal to proper signal...

Страница 70: ...ion of current generating 2 8 EXT TRIG connector 2 9 3 2 external calibration 4 2 to 4 3 F field wiring considerations 2 10 filtering See antialias filtering floating signal sources description 2 7 in...

Страница 71: ...quency 3 4 O onboard calibration reference specifications A 6 onboard current excitation generating with ICP circuitry 2 8 operation of NI 4472 See theory of operation overranged waveform 3 8 to 3 9 P...

Страница 72: ...A 8 power requirements A 7 safety A 9 signal conditioning A 6 triggers analog trigger A 7 digital trigger A 7 synchronizing multiple devices 2 11 to 2 12 system integration by National Instruments B...

Страница 73: ...User Manual inside region triggering mode figure 3 12 low hysteresis triggering mode figure 3 13 specifications analog trigger A 7 digital trigger A 7 U unpacking NI 4472 1 3 W Web support from Nation...

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