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National Instruments SCXI-1141 Скачать руководство пользователя страница 43

Chapter 4

Theory of Operation

SCXI-1141/1142/1143 User Manual

4-2

ni.com

The cutoff frequency of the filters and the output clock frequency are not
defined at power-up.

The block diagram in Figure 4-1 illustrates the key functional components
of the SCXI-1141/1142/1143 module.

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Содержание SCXI-1141

Страница 1: ...SCXI SCXI 1141 1142 1143 User Manual Eight Channel Lowpass Filter Modules SCXI 1141 1142 1143 User Manual October 2001 Edition Part Number 320748C 01...

Страница 2: ...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 7456 Malaysia 603 9...

Страница 3: ...ctions or service 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 n...

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: ...2 4 Connecting the SCXI 1141 1142 1143 Module to a DAQ Device for Multiplexed Scanning in an SCXI Chassis 2 6 Connecting the SCXI 1141 1142 1143 Module to a DAQ Device for Multiplexed Scanning in a PX...

Страница 7: ...Circuitry 4 4 Input Amplifiers 4 4 Correcting Gain and Offset Errors 4 5 Lowpass Filters 4 6 Filter Theory 4 6 Performance of the SCXI 1141 1142 1143 Module Filters 4 7 Magnitude Response 4 7 Phase Re...

Страница 8: ...istics 4 6 Figure 4 3 Real and Ideal Filter Responses to a Step Input Signal 4 7 Figure 4 4 Typical Magnitude Response of the SCXI 1141 1142 1143 Module Filters 4 8 Figure 4 5 Typical Passband Respons...

Страница 9: ...tion for the modules chassis and software SCXI user manuals Read these manuals next for detailed information about signal connections and module configuration SCXI user manuals explain in greater deta...

Страница 10: ...f precautions to take to avoid injury data loss or a system crash When this symbol is marked on the product see the Safety Information for precautions to take italic Italic text denotes variables emph...

Страница 11: ...National Instruments E Series MIO DAQ devices and with the SCXI 1200 data acquisition and control module You can use one DAQ device to control several SCXI 1141 1142 1143 modules in combination with o...

Страница 12: ...CXI 1141 1142 1143 User Manual NI DAQ Version 6 5 1 or later for the SCXI 1141 module Version 6 6 or later for the SCXI 1142 and SCXI 1143 modules Note To find the latest version of NI DAQ for your op...

Страница 13: ...eral components on the module Caution Never touch the exposed pins of connectors To avoid such damage in handling the module take the following precautions Ground yourself using a grounding strap or b...

Страница 14: ...mable gases or fumes Operate the product only at or below the pollution degree stated in Appendix A Specifications Pollution is foreign matter in a solid liquid or gaseous state that can reduce dielec...

Страница 15: ...tion category II are measurements on household appliances portable tools and similar equipment Installation category III is for measurements performed in the building installation This category is a d...

Страница 16: ...ding to the instructions on the CD and the DAQ Quick Start Guide included with the device Note It is important to install the NI DAQ driver software before installing the SCXI 1141 1142 1143 module to...

Страница 17: ...42 1143 module into a chassis that is turned on 3 Insert the SCXI 1141 1142 1143 module into an open slot in the SCXI chassis Gently guide the module into the slot guides and push it to the back of th...

Страница 18: ...any other SCXI modules should already be installed in the chassis according to their installation instructions You can connect the DAQ device to most modules in the chassis that are configured for mul...

Страница 19: ...bination Chassis Use this configuration to multiplex all eight channels of the SCXI 1141 1142 1143 module into a single channel of the DAQ device in a combination PXI chassis You need the following it...

Страница 20: ...ady installed the appropriate software you are ready to configure the SCXI 1141 1142 1143 module for multiplexed scanning See the Configuring and Testing the SCXI 1141 1142 1143 Module section later i...

Страница 21: ...1142 1143 module that is to be accessed in parallel mode by the DAQ device as described in the appropriate installation guide for the cable assembly 3 Connect the cable to the back of the cable adapte...

Страница 22: ...s an integer value you choose to uniquely identify the chassis for programming and scanning a Select the Chassis Address This is needed to address the chassis in a multichassis SCXI system Unless you...

Страница 23: ...e the module a Complete one of the following steps depending on whether the SCXI module is connected to a DAQ device If the selected module is connected to a DAQ device select that device by using the...

Страница 24: ...isplayed in the list Display the list of modules in the chassis by clicking the next to the chassis description 3 Right click the appropriate installation slot and select Insert 4 Select the module in...

Страница 25: ...inal configuration selections Perform the following steps to configure the SCXI 1141 1142 1143 module 1 Double click the Measurement Automation Explorer icon on the desktop 2 Display the list of insta...

Страница 26: ...of installed devices and interfaces by clicking the next to the Devices and Interfaces icon 3 From the list that appears locate the chassis you want to test Right click the chassis and click Test 4 If...

Страница 27: ...make sure the correct module is in the specified slot Delete the incorrect module as described in the Removing the SCXI 1141 1142 1143 Module from MAX section and then add the correct module as descr...

Страница 28: ...accessories for additional instructions and cautions To remove the SCXI 1141 1142 1143 module from an SCXI chassis perform the following steps while referring to Figure 2 3 1 Power off the SCXI chass...

Страница 29: ...aces icon 2 Locate the SCXI chassis in the list Display the list of modules in the chassis by clicking the next to the Chassis icon 3 Right click the module or chassis you want to delete and click Del...

Страница 30: ...an damage the SCXI 1141 1142 1143 module the SCXIbus any connected DAQ device and the computer with which the DAQ device is used NI is not liable for any damage resulting from such signal connections...

Страница 31: ...AGND NC AGND 15 NC NC NC 14 IN6 NC IN6 13 NC NC NC 12 IN7 NC IN7 11 NC NC NC 10 NC NC NC 9 NC NC NC 8 RSVD NC RSVD 7 NC NC NC 6 RSVD NC RSVD 5 NC NC NC 4 RSVD NC EXTCLK 3 NC NC NC 2 DGND NC OUTCLK 1 N...

Страница 32: ...V G The common mode input range of the SCXI 1141 1142 1143 module however is not a function of gain the differential input amplifier rejects common mode signals as long as the signal at both inputs i...

Страница 33: ...from the negative input to ground to provide a DC path for the input bias currents If you do not do this the bias currents of the instrumentation amplifiers of the nonreferenced channels charge up st...

Страница 34: ...ough necessary lowers the input impedance of the channel and introduces an additional DC offset voltage proportional to the product of the input bias current and the resistor value used The inputs of...

Страница 35: ...connect AC coupled signals Figure 3 3 Ground Referenced AC Coupled Signal Connection Figure 3 4 Ground Offset AC Coupled Signal Connection Figure 3 5 Floating AC Coupled Signal Connection IN IN 1 F 1...

Страница 36: ...TTL logic level or CMOS logic level square wave with a frequency of less than 2 5 MHz that is 100 times the desired cutoff frequency The absolute maximum input voltage for the EXTCLK pin is 5 5 V with...

Страница 37: ...ble extender with the SCXI 1141 1142 1143 module you should read this section Figure 3 6 shows the pin assignments for the SCXI 1141 1142 1143 module rear signal connector Pins without signal labels a...

Страница 38: ...nal taps into the SCXIbus D A line to indicate to the module whether the incoming serial stream is data or address information 29 SLOT0SEL Slot 0 select this signal taps into the SCXIbus INTR line to...

Страница 39: ...e the reference signals for outputs 1 through 7 Caution The SCXI 1141 1142 1143 module analog outputs are not overvoltage protected although they are short circuit protected Applying external voltage...

Страница 40: ...ne is being sent to Slot 0 SLOT0SEL 0 or to a module SLOT0SEL 1 Pin 37 is SERCLK and is equivalent to the SCXIbus SPICLK line Pin 37 is used to clock the serial data on the SERDATIN line into the modu...

Страница 41: ...e digital timing signals are pins 36 and 43 Pin 36 is SCANCLK the signal used as a clock for the SCXI 1141 1142 1143 module multiplexer counter The DAQ device pulses this signal at the end of each con...

Страница 42: ...and Butterworth filters respectively that can have a cutoff frequency from 10 Hz to 25 kHz All eight filters have the same cutoff frequency The outputs of all eight channels are available at the rear...

Страница 43: ...1 1142 1143 User Manual 4 2 ni com The cutoff frequency of the filters and the output clock frequency are not defined at power up The block diagram in Figure 4 1 illustrates the key functional compone...

Страница 44: ...Switch Digital Interface and Control 8 to 1 Mux Filter Input Protection Front Signal Connector SCXIbus Connector Calibration Selection Inst Amp Filter Bypass Input Protection Calibration Selection Ca...

Страница 45: ...EEPROM stores the calibration constants for each gain for all eight channels Information in the EEPROM is retained when the module is power off The SCXI 1141 1142 1143 module has calibration constants...

Страница 46: ...are determined and calibration constants are loaded into the EEPROM at the factory However gain errors drift with temperature changes You can add an additional set or subset of calibration constants...

Страница 47: ...ut without attenuation Because the SCXI 1141 1142 1143 modules use a lowpass filter this discussion is limited to lowpass filters The ideal lowpass filter does not attenuate any input signal frequency...

Страница 48: ...s examples of these responses to a step input Figure 4 3 Real and Ideal Filter Responses to a Step Input Signal Performance of the SCXI 1141 1142 1143 Module Filters The SCXI 1141 1142 1143 module is...

Страница 49: ...41 1142 1143 modules within the passband The passband magnitude response begins to drop off immediately for the SCXI 1142 module The SCXI 1141 performs much better than the SCXI 1142 in the passband b...

Страница 50: ...ency 1 In an ideal filter this would be a linear relationship Figure 4 7 shows the deviation of the actual phase response from an ideal linear response Generally phase response is described in terms o...

Страница 51: ...ilter The Bessel filter is designed for constant group delay at the expense of passband gain and stopband rolloff As a result the SCXI 1142 Bessel filter is the best choice when the phase information...

Страница 52: ...or of the SCXI 1141 1142 1143 Module Figure 4 8 Group Delay of the SCXI 1141 1142 1143 Module 0 0 5 1 1 5 2 100 0 100 200 300 Bessel 1142 Butterworth 1143 Elliptic 1141 Frequency normalized Phase Erro...

Страница 53: ...1143 module filter has an overshoot but it has less ringing than the SCXI 1141 You should consider the step response if the intended application is sensitive to overshoot or ringing See Table A 1 Set...

Страница 54: ...he cutoff frequency you specify and returns the actual cutoff frequency chosen The correct cutoff frequency depends on the application If phase nonlinearity ringing passband ripple or aliasing is a co...

Страница 55: ...rate This limiting frequency of one half the sample rate is known as the Nyquist frequency To prevent aliasing you must remove all signal components with frequencies greater than the Nyquist frequenc...

Страница 56: ...frequencies are necessary to prevent aliasing You can set the filter cutoff frequency closer to the sampling rate with the consequence of having some aliasing If you can tolerate aliasing in the tran...

Страница 57: ...h of 12 ranges of input frequencies The prefilters reduce signals that can alias into a lower frequency by at least 40 dB and the postfilters reconstruct the output waveform reducing high frequency im...

Страница 58: ...erload conditions caused by driving the output signal outside of the 5 V range and upon power up no data should be taken during the first 15 s Overload conditions result whenever the input signal exce...

Страница 59: ...y other module in multiplexed mode that is sending its output onto the SCXIbus You can also configure the SCXI 1141 1142 1143 module to send any one of its outputs to the SCXIbus Thus in multiplexed m...

Страница 60: ...1142 1143 module channels on a different pin and the module is in parallel mode In this mode you can use an SCXI 1180 feedthrough panel to make each of the outputs available at the front of the chass...

Страница 61: ...l input offset still exists and has a value of less than 6 V The offsets of the filters are compensated for internally generally only the offsets of the amplifiers need to be calibrated The filters sh...

Страница 62: ...nnels 8 differential Output signal range 5 V Channel gains software selectable 1 2 5 10 20 50 100 Input overvoltage protection Powered on 30 V Powered off 15 V Input coupling DC AC available with SCXI...

Страница 63: ...e 135 dB octave Cutoff frequency fc range 10 Hz to 25 kHz Cutoff choices software selectable Divided from 100 kHz or external clock for example 25 kHz 20 kHz 16 7 kHz 14 3 kHz or from external Passban...

Страница 64: ...et drift 10 V C Output offset drift 0 1 mV C Table A 1 Settling Time with Respect to Cutoff Frequency Module Bandwidth Step Response Settling Time in ms Full Scale Input Step 1 0 1 0 024 SCXI 1141 10...

Страница 65: ...ge 0 8 V max Digital output referenced to DIGGND VOH output logic high voltage 3 7 V min at 4 mA VOL output logic low voltage 0 4 V max at 4 mA Physical Dimensions 1 2 by 6 8 by 8 0 in 3 0 by 17 3 by...

Страница 66: ...patibility CE C Tick and FCC Part 15 Class A Compliant Electrical emissions EN 55011 Class A at 10 m FCC Part 15A above 1 GHz Electrical immunity Evaluated to EN 61326 1997 A1 1998 Table 1 Note For fu...

Страница 67: ...ess the 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...

Страница 68: ...Web sites 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...

Страница 69: ...ossary Prefix Meaning Value p pico 10 12 n nano 10 9 micro 10 6 m milli 10 3 k kilo 103 M mega 106 G giga 109 Numbers Symbols degrees greater than greater than or equal to less than less than or equal...

Страница 70: ...omponents ANSI American National Standards Institute AOGND GUARD analog output ground AOUT analog output signal AWG American Wire Gauge B bias current the small input current flowing into or out of th...

Страница 71: ...bels DC direct current DIGGND digital ground signal DIN Deutsche Industrie Norme German Industrial Standard DMM digital multimeter E EEPROM electrically erasable programmable read only memory EXTCLK e...

Страница 72: ...ls above that frequency M max maximum MB megabytes min minutes or minimum MIO multifunction I O MISO Master In Slave Out signal MOSI Master Out Slave In signal multiplex to route one of many input sig...

Страница 73: ...the ratio that a system attenuates signals in the stopband with respect to the passband usually defined in decibels per octave RSVD reserved signal bit S s seconds S s samples per second used to expre...

Страница 74: ...ANCLK scan clock signal SERCLK serial clock signal SERDATIN serial data in signal SERDATOUT serial data out signal SLOT0SEL slot 0 select signal SPICLK serial peripheral interface clock signal stopban...

Страница 75: ...nd referenced 3 4 ground referenced AC coupled 3 6 analog output multiplexed mode 4 18 parallel mode 4 19 signal connections 3 10 antialiasing filter using SCXI 1141 1142 1143 as 4 14 AOUT signal tabl...

Страница 76: ...4 6 environmental specifications A 5 EXTCLK signal description table 3 3 digital I O connections 3 7 external clock input for setting cutoff frequencies 4 15 F filter bypass mode 4 17 filter specifica...

Страница 77: ...143 as antialiasing filter 4 14 setting cutoff frequency 4 13 specifications A 2 transfer function characteristics figure 4 6 M magnitude response SCXI 1141 1142 1143 filters 4 7 typical magnitude res...

Страница 78: ...1141 1142 1143 pin equivalencies table 3 11 signal descriptions table 3 9 power up state 4 1 R rear signal connector analog output signal connections 3 10 digital I O signal connections emulation of...

Страница 79: ...tromagnetic compatibility A 5 environmental characteristics A 5 filter characteristics A 2 physical A 4 safety A 5 stability A 3 system noise A 3 stability specifications A 3 step input response of lo...

Страница 80: ...Index SCXI 1141 1142 1143 User Manual I 6 ni com U unpacking the SCXI 1141 1142 1143 2 1 W Web support from National Instruments B 1 worldwide technical support B 2...

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