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Chapter 2

Hardware Overview of the NI 78xxR

R Series Multifunction RIO User Manual

2-12

ni.com

Differential Connections for Nonreferenced or
Floating Signal Sources

Fig

re 2-7 shows how to connect a floating signal so

rce to a channel on

the NI 783

R/784

R/785

R config

red in DIFF inp

t mode.

Figure 2-7.

Differential Input Connections for Nonreferenced Signals

Fig

re 2-7 shows two bias resistors connected in parallel with the signal

leads of a floating signal so

rce. If yo

do not

se the resistors and the

rce is tr

ly floating, the so

rce might not remain within the

common-mode signal range of the instr

mentation amplifier, ca

sing

erroneo

s readings. Yo

st reference the so

rce to AIGND by

connecting the positive side of the signal to the positive inp

t of the

instr

mentation amplifier and connecting the negative side of the signal to

AIGND and to the negative inp

t of the instr

mentation amplifier witho

resistors. This connection works well for DC-co

pled so

rces with low

rce impedance, less than 100

For larger so

rce impedances, this connection leaves the differential signal

path significantly o

t of balance. Noise that co

ples electrostatically onto

the positive line does not co

ple onto the negative line beca

se it is

connected to gro

nd. Hence, this noise appears as a differential-mode

signal instead of a common-mode signal, and the instr

mentation amplifier

does not reject it. In this case, instead of directly connecting the negative

DIFF Input Mode Selected

–

AISENSE

AIGND

AI+

AI–

–

I/O Connector

Floating

Signal

Source

Bias

Current

Return

Paths

Measured

Voltage

Instrumentation

Amplifier

Bias
Resistors
(see text)

Содержание Multifunction RIO NI R Series

Страница 1: ...PXI 7813...

Страница 2: ...June 2009 370489G 01 Multifunction RIO NI R Series Multifunction RIO User Manual NI 781xR NI 783xR NI 784xR and NI 785xR Devices R Series Multifunction RIO User Manual ni com manuals Deutsch Fran ais...

Страница 3: ...banon 961 0 1 33 28 28 Malaysia 1800 887710 Mexico 01 800 010 0793 Netherlands 31 0 348 433 466 New Zealand 0800 553 322 Norway 47 0 66 90 76 60 Poland 48 22 328 90 10 Portugal 351 210 311 210 Russia...

Страница 4: ...uding photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National Instruments Corporation National Instruments re...

Страница 5: ...exible Functionality 1 4 User Defined I O Resources 1 4 Device Embedded Logic and Processing 1 4 Reconfigurable I O Architecture 1 5 Reconfigurable I O Applications 1 6 Software Development 1 6 LabVIE...

Страница 6: ...15 Common Mode Signal Rejection Considerations 2 16 Analog Output 2 16 Connecting Analog Output Signals 2 17 Digital I O 2 17 Connecting Digital I O Signals 2 17 RTSI Trigger Bus 2 21 PXI Local Bus NI...

Страница 7: ...Contents National Instruments Corporation vii R Series Multifunction RIO User Manual Appendix C Technical Support and Professional Services Glossary...

Страница 8: ...to take When symbol is marked on a product it denotes a warning advising you to take precautions to avoid electrical shock When symbol is marked on a product it denotes a component that may be hot To...

Страница 9: ...tion Getting Started with the LabVIEW Real Time Module Provides exercises to teach you how to develop a real time project and VIs from setting up RT targets to building debugging and deploying real ti...

Страница 10: ...he following documents contain information you might find helpful NI Developer Zone tutorial Field Wiring and Noise Considerations for Analog Signals at ni com zone PICMG CompactPCI 2 0 R3 0 PXI Hardw...

Страница 11: ...ice You can change the functionality of the FPGA on the R Series device in LabVIEW using the LabVIEW FPGA Module to create and download a custom virtual Table 1 1 NI 78xxR R Series Multifunction RIO D...

Страница 12: ...connected between devices R Series PXI devices access the RTSI bus through the PXI trigger lines implemented on the PXI backplane Refer to the NI R Series Multifunction RIO Specifications available at...

Страница 13: ...h level functions in hardware Refer to Chapter 2 Hardware Overview of the NI 78xxR for descriptions of the I O resources on the NI 78xxR Reconfigurable I O Concept R Series Multifunction RIO devices a...

Страница 14: ...ent timed loops with separate I O resources User Defined I O Resources You can create your own custom measurements using the fixed I O resources For example one application might require an event coun...

Страница 15: ...ments using the LabVIEW FPGA Module The FPGA logic provides timing triggering processing and custom I O measurements Each fixed I O resource used by the application uses a small portion of the FPGA lo...

Страница 16: ...es of FPGA VIs Software Development You can use LabVIEW with the LabVIEW FPGA Module to program the NI 78xxR To develop real time applications that control the NI 78xxR use LabVIEW with the LabVIEW Re...

Страница 17: ...ional Instruments NI RIO RIO Device Setup Help LabVIEW Real Time Module The LabVIEW Real Time Module extends the LabVIEW development environment to deliver deterministic real time performance You can...

Страница 18: ...8 68 RMIO NI Recommended 0 NI SCB 68 High performance shielded cable wired specifically for signal connection from the RMIO connector to the NI SCB 68 terminal block to provide higher signal integrity...

Страница 19: ...ielded cable is available from NI The SHC68 NT S connects to the NI 78xxR VHDCI connectors on one end of the cable The other end of the cable is not terminated This cable ships with a wire list identi...

Страница 20: ...ck diagram for the NI 7830R Figure 2 3 shows a block diagram for the NI 7831R 7833R 784xR 785xR Figure 2 1 NI 781xR Block Diagram Configuration Configuration Control Connector 0 DIO Connector 1 DIO Co...

Страница 21: ...nput Mode Mux AISENSE AIGND Calibration Mux Voltage Reference Temperature Sensor Calibration DACs 2 x4 Channels 16 Bit DAC Digital I O 16 User Configurable FPGA on RIO Devices Bus Interface Data Addre...

Страница 22: ...t AO channels 56 bidirectional DIO lines that you can configure individually for input or output and a Virtex II XC2V1000 FPGA AI AI PCI PXI CompactPCI Bus Input Mux Instrumentation Amplifier Input Mo...

Страница 23: ...ght independent 16 bit AI channels eight independent 16 bit AO channels and 96 bidirectional DIO lines that you can configure individually for input or output The NI PXI 7851R has a Virtex 5 LX30 FPGA...

Страница 24: ...uses two AI lines The positive input pin connects to the positive terminal of the onboard instrumentation amplifier The negative input pin connects to the negative input of the instrumentation amplif...

Страница 25: ...ut of the instrumentation amplifier for each channel In RSE input mode the negative input of the instrumentation amplifier for each channel is internally connected to AIGND In NRSE input mode the AISE...

Страница 26: ...tive and negative inputs of the instrumentation amplifier The instrumentation amplifier converts two input signals to a signal that is the difference between the two input signals The amplifier output...

Страница 27: ...put signal varies as the source floats out of the common mode input range Ground Referenced Signal Sources A ground referenced signal source is connected to the building system ground so it is already...

Страница 28: ...resistors V1 AI i AIGND i V1 AI Vg AIGND Ground loop losses Vg are added to measured signal NOT RECOMMENDED V1 AI i AI i AIGND i V1 AI i AI i AIGND i See text for information on bias resistors Signal...

Страница 29: ...erence signal or return connects to the negative input of the instrumentation amplifier Use differential input connections for any channel that meets any of the following conditions The input signal i...

Страница 30: ...he ground potential difference between the signal source and the NI 783xR 784xR 785xR ground shown as Vcm in Figure 2 6 In addition the instrumentation amplifier can reject common mode noise pickup in...

Страница 31: ...ve side of the signal to the positive input of the instrumentation amplifier and connecting the negative side of the signal to AIGND and to the negative input of the instrumentation amplifier without...

Страница 32: ...nstrumentation amplifier to work If the source is AC coupled capacitively coupled the instrumentation amplifier needs a resistor between the positive input and AIGND If the source has low impedance ch...

Страница 33: ...R 785xR should not supply one In single ended input modes electrostatic and magnetic noise couples into the signal connections more than in differential input modes The coupling is the result of diffe...

Страница 34: ...ntial difference between the NI 783xR 784xR 785xR ground and the signal ground appears as a common mode signal at both the positive and negative inputs of the instrumentation amplifier The instrumenta...

Страница 35: ...ni com manuals for more information about input ranges Analog Output The bipolar output range of the NI 783xR 784xR 785xR AO channels is fixed at 10 V Some applications require that the AO channels po...

Страница 36: ...for either input or output When the system powers on the DIO lines are at high impedance To set another power on state you can configure the NI 78xxR to load a VI when the system powers on The VI can...

Страница 37: ...rnal pull up resistor to 5 V This resistor pulls up the 3 3 V digital output from the NI 78xxR to 5 V CMOS logic levels Refer to the NI R Series Multifunction RIO Specifications available at ni com ma...

Страница 38: ...of the switch shown in Figure 2 11 Digital output applications include sending TTL or LVCMOS signals and driving external devices such as the LED shown in Figure 2 11 The NI 78xxR SHC68 68 RDIO cable...

Страница 39: ...Examples of high frequency or edge sensitive signals include clock trigger pulse width modulation PWM encoder and counter signals Examples of static signals or non edge sensitive low frequency signals...

Страница 40: ...or an output signal Because each trigger line on the RTSI bus is connected in parallel to all the other RTSI devices on the bus only one device should drive a particular RTSI trigger line at a time Fo...

Страница 41: ...g LVTTL and LVCMOS levels Caution Do not enable the local bus lines on an adjacent device if the device drives anything other than 0 3 3V LVTTL signal levels on the NI PXI 781xR 783xR Enabling the lin...

Страница 42: ...re 2 16 for the location of switches on the NI PXI 783xR For normal operation SW1 is in the OFF position To prevent a VI stored in Flash memory from loading to the FPGA at power up move SW1 to the ON...

Страница 43: ...8xxR R Series Multifunction RIO User Manual 2 24 ni com Figure 2 13 Switch Location on the NI PCI 781xR Figure 2 14 Switch Location on the NI PXI 781xR SW1 SW2 SW3 NI PXI 7811R Reconfigurable I O CONN...

Страница 44: ...National Instruments Corporation 2 25 R Series Multifunction RIO User Manual Figure 2 15 Switch Location on the NI PCI 783xR Figure 2 16 Switch Location on the NI PXI 783xR SW1 SW2 SW3 SW1 SW2 SW3 CO...

Страница 45: ...essary To return to the defaults of loading from Flash memory repeat the previous procedure but return SW1 to the OFF position in step 3 You can use this switch to enable disable the ability to load f...

Страница 46: ...rminals and replace the fuse as described in the Device Fuse Replacement NI 784xR 785xR Only section Caution Never connect the 5 V power terminals to analog or digital ground or to any other voltage s...

Страница 47: ...on the 5 V terminal When to Use the Disk Drive Power Connector PCI Express R Series devices without the disk drive power connector installed perform identically to other R Series devices for most appl...

Страница 48: ...able on the disk drive power connectors in a computer can vary For example consider using a disk drive power connector that is not in the same power chain as the hard drive Figure 2 19 Connecting to t...

Страница 49: ...traveling through areas with large magnetic fields or high electromagnetic interference Route signals to the device carefully Keep cabling away from noise sources The most common noise source in a PXI...

Страница 50: ...most difficult and most accurate Loading Calibration Constants The NI 783xR 784xR 785xR is factory calibrated before shipment at approximately 25 C to the levels indicated in the device specifications...

Страница 51: ...e a small amount of gain error and self calibration is sufficient The Flash memory on the NI 783xR 784xR 785xR stores the results of a self calibration so the CalDACs automatically load with the newly...

Страница 52: ...ion RIO User Manual To externally calibrate your device use an external reference several times more accurate than the device itself For more information on externally calibrating your NI 783xR 784xR...

Страница 53: ...I O connectors Figure A 1 shows the I O connector pin assignments and locations for NI PCI 7811R 7813R and NI PXI 7811R 7813R Figure A 2 shows the I O connector pin assignments and locations for NI P...

Страница 54: ...O12 DIO13 DIO14 DIO15 DIO16 DIO17 DIO18 DIO19 DIO20 DIO21 DIO22 DIO23 DIO24 DIO25 DIO26 DIO27 DIO29 DIO30 DIO32 DIO34 DIO36 DIO38 35 1 36 2 37 3 38 4 39 5 40 6 41 7 42 8 43 9 44 10 45 11 46 12 47 13 4...

Страница 55: ...20 55 21 56 22 57 23 58 24 59 25 60 26 61 27 62 28 63 29 64 30 65 31 66 32 67 33 68 34 1No Connect on the NI 7830R DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND DGND...

Страница 56: ...the reference point for single ended measurements in RSE configuration and the bias current return point for differential measurements All three ground references AIGND AOGND and DGND are connected t...

Страница 57: ...ce Input Output Protection Volts On Off Source mA at V Sink mA at V Rise Time Bias 5V DO Analog Signals NI 783xR 784xR 785xR Only AI 0 7 AI 10 G in parallelwith 100 pF 42 35 2 nA AI 0 7 AI 10 G in par...

Страница 58: ...de when using 5B signal conditioning The other 26 pin header contains all the NI 783xR 784xR 785xR analog output signals You can plug this connector directly into a 5B backplane for AO signal conditio...

Страница 59: ...4 AOGND4 AO5 AO6 AOGND6 AO7 No Connect No Connect No Connect AOGND1 No Connect No Connect AOGND3 No Connect No Connect AOGND5 No Connect No Connect AOGND7 No Connect 2 4 6 8 10 12 14 16 18 20 22 24 26...

Страница 60: ...the NSC68 5050 Cable 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 DIO23 DIO22 DIO21 DIO20 DIO19 DIO18 D...

Страница 61: ...o Figure B 1 for the general purpose switch configuration Figure B 1 General Purpose Switch Configuration for the SCB 68 Terminal Block After configuring the SCB 68 switches you can connect the I O si...

Страница 62: ...tandard Service Program Membership This program entitles members to direct access to NI Applications Engineers via phone and email for one to one technical support as well as exclusive access to on de...

Страница 63: ...r product by visiting ni com certification Calibration Certificate If your product supports calibration you can obtain the calibration certificate for your product at ni com calibration If you searche...

Страница 64: ...fix 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 to Negative of or...

Страница 65: ...ground signal AISENSE Analog input sense signal AO Analog output AO i Analog output channel signal AOGND Analog output ground signal B bipolar A signal range that includes both positive and negative...

Страница 66: ...verts a digital number into a corresponding analog voltage or current DAQ Data acquisition A system that uses the computer to collect receive and generate electrical signals dB Decibel The unit for ex...

Страница 67: ...ality of the hardware G glitch An unwanted signal excursion of short duration that is usually unavoidable H h Hour HIL Hardware in the loop Hz Hertz I I O Input output The transfer of data to from a c...

Страница 68: ...alog input channel N noise An undesirable electrical signal Noise comes from external sources such as the AC power line motors generators transformers fluorescent lights CRT displays computers electri...

Страница 69: ...strumentation An open specification that builds off the CompactPCI specification by adding instrumentation specific features R RAM Random access memory The generic term for the read write memory that...

Страница 70: ...gnal frequencies T THD Total harmonic distortion The ratio of the total rms signal due to harmonic distortion to the overall rms signal in decibel or a percentage thermocouple A temperature sensor cre...

Страница 71: ...ries Multifunction RIO User Manual G 8 National Instruments Corporation VOH Volts output high VOL Volts output low Vrms Volts root mean square W waveform Multiple voltage readings taken at a specific...

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