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National Instruments NI 4472 User Manual Download Page 41

Chapter 3

Device Overview and Theory of Operation

NI 4472 User Manual

3-14

ni.com

Device and Clocks

♦

NI 4472 for PXI/CompactPCI

The NI 4472 for PXI/CompactPCI can use either its internal DDS timebase
or a timebase received from another NI 4472 over the PXI backplane. If
you configure the NI 4472 to use the internal timebase and place the
NI 4472 in slot 2, you can program the device to drive its internal timebase
over the PXI backplane to another NI 4472 that you program 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 4472 for PCI

The NI 4472 for PCI can use either its internal DDS timebase or a timebase
received over the RTSI bus. If you configure the NI 4472 to use the internal
timebase, you can program the NI 4472 to drive its internal timebase over
the RTSI bus to another NI 4472 that you program to receive this timebase
signal. The default configuration at startup is to use the internal timebase
without driving the RTSI bus timebase signal. This timebase is software
selectable.

Summary of Contents for NI 4472

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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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