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Chapter 4

Theory of Operation

SCXI-1120/D User Manual

4-10

www.natinst.com

In the parallel-output mode, the counter is disabled and amplifier channel 0 
is selected at the output multiplexer and is connected to MCH0. The seven 
other channels are hardwired to MCH1 through MCH7 on the rear 
connector.

The output multiplexer multiplexes all eight amplifier outputs and the 
temperature-sensor reading provided on the MTEMP line. This 
measurement is only software controlled. For hardware control of the 
temperature sensor reading, connect the temperature sensor to pin 18 on the 
rear connector as described in Chapter 2, 

Configuration and Installation

. 

The multiplexer output connects to the MCH0± and is connected to the 
DAQ device analog channel input. In the case of the MIO DAQ devices, 
MCH0± on the rear connector corresponds to ACH0 and ACH8. 

Notice that when the multiplexed-output mode is selected, pins 5 
through 18 on the rear connector are still driven by the SCXI-1120/D. The 
SCXI-1120/D outputs on the rear connector are short-circuit protected.

Parallel Mode

When the MCH0 signal is configured to be the output of channel 0, the rear 
connector simultaneously carries each of the outputs of the SCXI-1120/D 
on different pins, 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 chassis. A DAQ device cabled to an SCXI-1120/D in 
parallel mode reads a separate output signal from the module on each of its 
analog inputs. You cannot multiplex the parallel outputs of a module onto 
the SCXIbus; only a DAQ device directly cabled to the module has access 
to the outputs.

Multiplexed Mode (Recommended)

In multiplexed mode, the output signals for channels 1 through 7 are sent 
to the rear connector but are usually ignored. All reads from the module are 
from the MCH0 signal of the rear connector, which can be configured as 
the output of any channel of the SCXI-1120/D or as the output of any other 
module in multiplexed mode that is sending its output onto the SCXIbus. 
You can also configure the SCXI-1120/D to send any one of its outputs to 
the SCXIbus. Thus, in multiplexed mode only, one module in a chassis 
needs to be connected to a DAQ device; you can pass signals from the other 
modules to the DAQ device through the SCXIbus.

Содержание 776570-00

Страница 1: ...120 D User Manual Eight Channel Isolated Analog Input Module and Eight Channel Wide Band Isolated Analog Input Module for Signal Conditioning SCXI 1120 D User Manual September 1999 Edition Part Number...

Страница 2: ...1 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 Mexico D F 5 280 7625 Mexico Mont...

Страница 3: ...ilures 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 and po...

Страница 4: ...tal Signal Connections 2 4 Using Jumpers W42 and W43 2 5 Using Jumper W44 on Revisions A and B of the SCXI 1120 2 6 Using Jumper W44 on Revision C of the SCXI 1120 and All Revisions of the SCXI 1120D...

Страница 5: ...nt Requirements 5 1 Offset Null Adjust 5 1 Appendix A Specifications Appendix B Technical Support Resources Glossary Index Figures Figure 1 1 The Relationship between the Programming Environment NI DA...

Страница 6: ...l 4 4 Figure 4 4 Analog Input Block Diagram 4 6 Figure 4 5 Analog Output Circuitry 4 9 Tables Table 2 1 Digital Signal Connections Jumper Settings 2 7 Table 2 2 Jumper W46 Settings 2 9 Table 2 3 Jumpe...

Страница 7: ...signed for low cost signal conditioning of volt millivolt and current sources that require a 20 kHz bandwidth and where high common mode voltages exist Conventions The following conventions appear in...

Страница 8: ...s Your DAQ hardware documentation This documentation has detailed information about the DAQ hardware that plugs into or is connected to your computer Use this documentation for hardware installation a...

Страница 9: ...lel output mode with all eight input channels connected in parallel to eight DAQ device channels or in the multiplexed output mode with all eight channels multiplexed into a single DAQ device channel...

Страница 10: ...g Detailed specifications of the SCXI 1120 D are listed in Appendix A Specifications What You Need to Get Started To set up and use your SCXI 1120 D you will need the following items SCXI 1120 or SCXI...

Страница 11: ...ogramming Choices There are several options to choose from when programming your National Instruments plug in DAQ and SCXI hardware You can use LabVIEW LabWindows CVI NI DAQ ComponentWorks Measure Vir...

Страница 12: ...irtualBench software will greatly reduce the development time for your data acquisition and control application NI DAQ Driver Software The NI DAQ driver software is included at no charge with all Nati...

Страница 13: ...r kit SCXI modules and accessories for isolating amplifying exciting and multiplexing signals for relays and analog output With SCXI you can condition and acquire up to 3 072 channels For additional i...

Страница 14: ...ser Manual 2 Configuration and Installation This chapter describes how to configure the SCXI 1120 D jumpers and how to install the SCXI 1120 D into the SCXI chassis Module Configuration The SCXI 1120...

Страница 15: ...Null Adjust Potentiometers Output Null Adjust Potentiometers Product Name Assembly Number and Serial Number Front Connector Second Stage Filter Jumpers Second Stage Gain Jumpers First Stage Filter Ju...

Страница 16: ...part number and is the letter found in that part number User configurable jumpers Jumper W43 carries the SCXIbus MISO line after buffering to the SERDATOUT signal on the rear signal connector On all...

Страница 17: ...down 3 Remove the jumpers you want to change and replace them on the appropriate pins 4 Snap the top cover back in place 5 Replace the grounding screw to ensure proper shielding You must use software...

Страница 18: ...ns A and B of the SCXI 1120 On Revision A and B SCXI 1120 modules jumper W42 is not used Set jumper W43 as explained in the cases above except in the case of a multichassis ribbon cable system In a mu...

Страница 19: ...to the DAQ device Set jumper W42 to position 1 on only one of the SCXI 1120 D modules cabled to the DAQ device All the other SCXI 1120 D modules that are cabled to the DAQ device should have jumper W...

Страница 20: ...ption Configuration W42 Position 1 Connects pullup to SERDATOUT factory default setting Applies only to SCXI 1120 Revisions C or later and all SCXI 1120D modules W42 Position 3 Parking position not co...

Страница 21: ...rounding Shielding and Reference Mode Selection Jumper W46 Note The SCXI 1120 D will drive pins 4 6 8 10 12 14 16 and 18 on the rear signal connector although the SCXI 1120 D is in multiplexed mode W4...

Страница 22: ...the analog reference to AOGND pins 1 and 2 of the rear signal connector Use with RSE DAQ devices Do not use with DIFF differential input DAQ devices AB R1 Connects SCXIbus guard to the analog referen...

Страница 23: ...3 Jumper W41 Settings Description Configuration Position 1 Temperature sensor accessed in MTS mode factory default setting Position 3 Temperature sensor accessed in DTS mode DAQ device configured for...

Страница 24: ...appropriate jumper on your module to the position indicated in Tables 2 3 and 2 4 Refer to Figure 2 1 for jumper locations on your module To determine the overall gain of a given channel on the SCXI 1...

Страница 25: ...igher signal to noise ratio Furthermore two filter bandwidths are available 10 kHz and 4 Hz Second stage 1 A 2 B 5 C 10 D factory default setting for the SCXI 1120 20 E factory default setting for the...

Страница 26: ...nel Two stage filtering eliminates the noise generated by the isolation amplifier producing a higher signal to noise ratio Furthermore two filter bandwidths are available 22 5 kHz and 4 5 kHz Your SCX...

Страница 27: ...til the connectors make contact If you have already installed a cable assembly in the rear of the chassis the module and cable assembly must be firmly engaged however do not force the module into plac...

Страница 28: ...r prior to removing covers or shields Equipment described in this document must be used in an Installation Category II environment per IEC 664 This category requires local level supply mains connected...

Страница 29: ...the host computer and the SCXI device National Instruments is not liable for any damages or injuries resulting from incorrect signal connections If high voltages 30 Vrms and 42 4 Vpeak or 60 VDC are...

Страница 30: ...for the SCXI 1120 D front connector Figure 3 1 SCXI 1120 D Front Connector Pin Assignments CHSGND 5 V RSVD CH7 CH6 CH5 CH4 CH3 CH2 CH1 NC NC NC NC NC CH0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 2...

Страница 31: ...the rear signal connector MCH7 when the terminal block is configured for direct temperature connection and jumper W41 is in position 3 A4 5 V 5 VDC Source Powers temperature sensor on the terminal blo...

Страница 32: ...ltage up to 250 Vrms For better noise immunity connect the negative input channel to the signal reference If the measured signals are floating connect the negative input channel to chassis ground on t...

Страница 33: ...is solution although necessary in this case lowers the input impedance of the input channel amplifier and introduces an additional offset voltage proportional to the input bias current and to the resi...

Страница 34: ...1120D you do not need to add the external resistor as the SCXI 1120D provides a DC path internally Refer to Figures 3 6 and 3 7 for further details Figure 3 6 AC Coupled Signal Connection for the SCX...

Страница 35: ...able extender with the SCXI 1120 D you should read this section Figure 3 8 shows the pin assignments for the SCXI 1120 D rear signal connector Figure 3 8 SCXI 1120 D Rear Signal Connector Pin Assignme...

Страница 36: ...4 33 DIG GND Digital Ground Supply the reference for DAQ device digital signals and are tied to the module digital ground 25 SERDATIN Serial Data In Taps into the SCXIbus MOSI line to provide serial i...

Страница 37: ...factory default setting or in position AB R1 to avoid ground loops With DAQ devices that are configured for RSE measurements jumper W46 should be in position AB R0 to connect the SCXI 1120 D analog g...

Страница 38: ...nP device respectively Table 3 3 lists the equivalencies For more information consult your cable assembly installation guide Specifications and ratings for the digital I O lines are given in Appendix...

Страница 39: ...unit making up the SCXI 1120 D Functional Overview The block diagram in Figure 4 1 illustrates the key functional components of the SCXI 1120 D Figure 4 1 SCXI 1120 D Block Diagram Timing and Analog O...

Страница 40: ...er channels with gains of 1 2 5 10 20 50 100 200 250 500 1 000 and 2 000 The SCXI 1120D consists of eight isolated amplifier channels with gains of 0 5 1 2 5 5 10 25 50 100 125 250 500 and 1 000 The S...

Страница 41: ...a data acquisition section and an SCXIbus section The SCXI 1120 D connects to the SCXIbus through a 4 24 metral receptacle and to the DAQ device through a 50 pin ribbon cable header The digital inter...

Страница 42: ...ptions All the control bits are fed into a latch before being routed to the rest of the module The channel select bits are taken directly from the shift register The Module ID Register contains the mo...

Страница 43: ...og bus AB0 and a chassis ground CHSGND AB0 buses the SCXI 1120 D output to other modules or receives outputs from other modules through the SCXIbus The guard guards the analog bus and can be connected...

Страница 44: ...hannel 1 Input Channel 2 Input Channel 3 Input Channel 4 Input Channel 5 Input Channel 6 Input Channel 7 To Output Stage To Output Stage To Output Stage To Output Stage To Output Stage To Output Stage...

Страница 45: ...given gain stage use the following formula where BW is a given amplifier stage bandwidth GBWP is the gain bandwidth product typically 800 kHz for the SCXI 1120 and 8 MHz for the SCXI 1120D and G is t...

Страница 46: ...mmon mode voltage or noise before being sampled and converted by the DAQ device The isolated amplifier also amplifies and conditions an input signal which results in an increase in measurement resolut...

Страница 47: ...ts of a buffered output multiplexer and channel select hardware The channel select hardware consists of a counter This counter is needed when the module is operating in the multiplexed output mode Rea...

Страница 48: ...e When the MCH0 signal is configured to be the output of channel 0 the rear connector simultaneously carries each of the outputs of the SCXI 1120 D on different pins and the module is in parallel mode...

Страница 49: ...ch module sends its output to the SCXIbus during a scan You can specify this list to scan the modules in any order with an arbitrary number of channels for each module entry in the list However the ch...

Страница 50: ...ital multimeter DMM Each channel on the SCXI 1120 D has two potentiometers dedicated for calibration One potentiometer is used to null the output offset the other is used to null the input offset Re c...

Страница 51: ...amplifier gain to 1 000 10 Adjust the input potentiometer of the desired channel until the output is 0 6 mV 11 Go to the next channel You may seal the potentiometers after calibration with antisabotag...

Страница 52: ...s 0 to 50 C SCXI 1120 Analog Input Gain jumper selectable 1 2 5 10 20 50 100 200 250 500 1 000 2 000 Output range 5 V Number of channels 8 Gain accuracy 0 2 of reading typ 0 6 of reading max Nonlinear...

Страница 53: ...0 15 V s Noise 400 kHz bandwidth 1 Input gain 1 000 4 Hz filter 100 nVrms 10 kHz filter 4 Vrms Output gain 1 4 Hz 150 Vrms 10 kHz 1 mVrms Operating common mode voltage 50 or 60 Hz Channel to channel o...

Страница 54: ...voltage 0 8 V max I I input current leakage 1 A max Digital output specifications referenced to DIG GND V OH output logic high voltage 3 7 V min at 4 mA max V OL output logic low voltage 0 4 V max at...

Страница 55: ...1120 D User Manual A 4 www natinst com Safety Designed in accordance with IEC 61010 1 UL3111 1 and CAN CSA C22 2 No 1010 1 for electrical measuring and test equipment Approved at altitudes up to 2000...

Страница 56: ...1329 or SCXI 1305 Maximum working voltage Signal CMV 250 Vrms Overvoltage protection 250 Vrms on or off Table A 1 Input Signal Range Gain Range Channel Bandwidth Filter at 22 5 K Filter at 4 5 K 0 5 1...

Страница 57: ...eristics Input impedance Power on 1 M Power off and overvoltaged 500 k Input bias current 15 pA CMRR at DC1 110 dB CMRR at 50 or 60 Hz1 98 dB Output range 5 V Output impedance 100 in multiplexed mode...

Страница 58: ...5 1 5 at 3 mVrms f 1 kHz G 1 000 Crosstalk 50 load and source 80 dB at 1 kHz Output selection time with V step all gains to 0 012 accuracy 3 s Filter Type Second order low pass RC filter Cutoff freque...

Страница 59: ...c high voltage 3 7 V min at 4 mA max V OL output logic low voltage 0 4 V max at 4 mA max Physical Dimensions 3 1 by 17 3 by 20 3 cm 1 2 by 6 8 by 8 0 in Connectors 50 pin male ribbon cable rear connec...

Страница 60: ...ons FAQs and their corresponding answers or solutions including special sections devoted to our newest products The database is updated daily in response to new customer experiences and feedback Troub...

Страница 61: ...ite to provide information on local services You can access these Web sites from www natinst com worldwide If you have trouble connecting to our Web site please contact your local National Instruments...

Страница 62: ...103 M mega 106 Numbers Symbols degrees ohms 5 V signal 5 VDC Source signal A A amperes AB0 Positive Analog Bus 0 signal AB0 Negative Analog Bus 0 signal AB0EN Analog Bus 0 Enable bit ACH data acquisit...

Страница 63: ...bit CHS Chassis bit CHSGND Chassis Ground signal CJR cold junction reference CLKEN Clock Enable bit CLKOUTEN Scan Clock Output Enable bit CLKSELECT Scan Clock Select bit CNT Count bit D D A Data Addre...

Страница 64: ...emperature sensor F F Fahrenheit FIFO first in first out FOUTEN Forced Output Enable bit FRT Forced Retransmit bit G GBWP gain bandwidth product GUARD Guard signal H hex hexadecimal HSCR Hardscan Cont...

Страница 65: ...MCH Positive Analog Output Channel Number signal MCH Negative Analog Output Channel Number signal MIO multifunction I O MISO Master In Slave Out signal MOD Module Number bit MOSI Master Out Slave In...

Страница 66: ...access memory RD Read bit RESET Reset signal rms root mean square RSC rear signal connector RSE referenced single ended input RSVD Reserved bit signal RTD resistance temperature detector RTEMP Read T...

Страница 67: ...t s seconds SERCLK Serial Clock signal SERDATIN Serial Data In signal SERDATOUT Serial Data Out signal SL Slot bit SLOT0SEL Slot 0 Select signal SPI Serial Peripheral Interface SPICLK Serial Periphera...

Страница 68: ...ments Corporation G 7 SCXI 1120 D User Manual VDC volts direct current VIH input logic high voltage VIL input logic low voltage VOH output logic high voltage VOL output logic low voltage Vrms volts ro...

Страница 69: ...upled signalconnections figure 3 6 SCXI 1120D AC coupled signal connections figure 3 7 description 3 7 floating AC coupled signalconnections figure 3 7 SCXI 1120 D description 3 5 floating signal conn...

Страница 70: ...description table 3 9 SCXIbus to SCXI 1120 D to DAQ device pin equivalencies table 3 11 diagnostic resources online B 1 DIG GND signal table 3 9 digital control circuitry 4 4 digital interface circuit...

Страница 71: ...n 2 8 to 2 13 gain jumpers 2 10 to 2 12 jumper W41 direct temperature connection 2 10 jumper W46 grounding shielding and reference mode selection 2 8 to 2 9 SCXI 1120 filter jumpers 2 12 to 2 13 SCXI...

Страница 72: ...state 4 2 requirements for getting started 1 2 revision letter location note 2 3 software programming choices 1 3 to 1 5 National Instruments application software 1 3 to 1 4 NI DAQ driver software 1 4...

Страница 73: ...ation 4 1 to 4 11 analog and timing circuitry 4 5 to 4 11 analog input channels figure 4 6 analog output circuitry 4 9 to 4 11 formula for gain determination 4 7 block diagram of SCXI 1120 D 4 1 digit...

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