Reconfigurable I/O NI 7831R User Manual Reconfigurable I/O Devices for PCI/PXI/CompactPCI Bus Computers NI 7831R User Manual April 2004 Edition Part Number 370489B-01
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Important Information Warranty The NI 7831R is warranted against defects in materials and workmanship for a period of one year from the date of shipment, as evidenced by receipts or other documentation. National Instruments will, at its option, repair or replace equipment that proves to be defective during the warranty period. This warranty includes parts and labor.
Compliance Compliance with FCC/Canada Radio Frequency Interference Regulations Determining FCC Class The Federal Communications Commission (FCC) has rules to protect wireless communications from interference. The FCC places digital electronics into two classes. These classes are known as Class A (for use in industrial-commercial locations only) or Class B (for use in residential or commercial locations). All National Instruments (NI) products are FCC Class A products.
Contents About This Manual Conventions ...................................................................................................................vii Reconfigurable I/O Documentation...............................................................................viii Related Documentation..................................................................................................ix Chapter 1 Introduction About the NI 7831R..........................................................................
Contents Single-Ended Connection Considerations ...................................................... 2-12 Single-Ended Connections for Floating Signal Sources (RSE Input Mode).......................................................................... 2-13 Single-Ended Connections for Grounded Signal Sources (NRSE Input Mode)....................................................................... 2-13 Common-Mode Signal Rejection Considerations........................................... 2-14 Analog Output .
About This Manual This manual describes the electrical and mechanical aspects of the National Instruments 7831R device and contains information concerning its operation and programming. The NI 7831R device is a Reconfigurable I/O (RIO) device. The NI 7831R has eight independent, 16-bit analog input (AI) channels, eight independent, 16-bit analog output (AO) channels, and 96 digital I/O (DIO) lines.
About This Manual programs, subprograms, subroutines, device names, functions, operations, variables, filenames, and extensions. Reconfigurable I/O Documentation The NI 7831R User Manual is one piece of the documentation set for your RIO system and application. Depending on the hardware and software you use for your application, you could have any of several types of documentation.
About This Manual Related Documentation The 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 Hardware Specification Revision 2.1 • PXI Software Specification Revision 2.
1 Introduction This chapter describes the NI 7831R, describes the concept of the Reconfigurable I/O device, describes the optional software and equipment, and contains information about the NI 7831R. About the NI 7831R The NI 7831R is an R Series device with 96 digital I/O (DIO) lines, eight independent, 16-bit analog output (AO) channels, and eight independent, 16-bit analog input (AI) channels.
Chapter 1 Introduction between devices. The NI PXI-7831R accesses the RTSI bus through the PXI trigger lines implemented on the PXI backplane. Refer to Appendix A, Specifications, for detailed NI 7831R specifications. Using PXI with CompactPCI Using PXI-compatible products with standard CompactPCI products is an important feature provided by PXI Hardware Specification Revision 2.1 and PXI Software Specification Revision 2.1.
Chapter 1 Introduction Table 1-1. Pins Used by the NI PXI-7831R NI PXI-7831R Signal PXI Pin Name PXI J2 Pin Number PXI Trigger<0..7> PXI Trigger<0..7> A16, A17, A18, B15, B18, C18, E16, E18 PXI Clock 10 MHz PXI Clock 10 MHz E17 PXI Star Trigger PXI Star Trigger D17 LBLSTAR<0..12> LBL<0..12> A1, A19, C1, C19, C20, D1, D2, D15, D19, E1, E2, E19, E20 LBR<0..12> LBR<0..
Chapter 1 Introduction 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 counter that increments when a rising edge appears on any of three digital input lines. Another application might require a digital line to be asserted after an analog input exceeds a programmable threshold. Device-Embedded Logic and Processing You can implement LabVIEW logic and processing in the FPGA of the R Series device.
Chapter 1 Introduction 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 logic that controls the fixed I/O resource. The bus interface also uses a small portion of the FPGA logic to provide software access to the device. The remaining FPGA logic is available for higher level functions such as timing, triggering, and counting. The functions use varied amounts of logic.
Chapter 1 Introduction You can use Interactive Front Panel Communication to communicate directly with the VI running on the FPGA. You can use Programmatic FPGA Interface Communication to programmatically control and communicate with FPGA VIs from host VIs. Use the FPGA Interface functions when you target LabVIEW for Windows or an RT target to create host VIs that wait for interrupts and control the FPGA by reading and writing the FPGA VI running on the R Series device.
Chapter 1 Introduction Cables and Optional Equipment National Instruments offers a variety of products you can use with R Series devices, including cables, connector blocks, and other accessories, as shown in Table 1-2. Table 1-2. Cables and Accessories Cable SH68-C68-S NI 7831R Connector Cable Description Shielded 68-pin VHDCI male connector to female 0.050 series D-type connector. The cable is constructed with 34 twisted wire pairs and an overall shield.
Chapter 1 Introduction Table 1-2. Cables and Accessories (Continued) Cable NSC68-262650 NI 7831R Connector Cable Description Non-shielded cable connects from 68-pin VHDCI male connector to two 26-pin female headers plus one 50-pin female header. The pinout of these headers allows for direct connection to 5B backplanes for analog signal conditioning and SSR backplanes for digital signal conditioning.
Chapter 1 Introduction Safety Information The following section contains important safety information that you must follow when installing and using the NI 7831R. Do not operate the NI 7831R in a manner not specified in this document. Misuse of the NI 7831R can result in a hazard. You can compromise the safety protection built into the NI 7831R if the NI 7831R is damaged in any way. If the NI 7831R is damaged, return it to NI for repair.
Chapter 1 Introduction Operate the NI 7831R at or below the installation category1 listed in the section Maximum working voltage, in Appendix A, Specifications. Measurement circuits are subjected to working voltages2 and transient stresses (overvoltage) from the circuit to which they are connected during measurement or test. Installation categories establish standard impulse withstand voltage levels that commonly occur in electrical distribution systems.
2 Hardware Overview of the NI 7831R This chapter presents an overview of the hardware functions and I/O connectors on the NI 7831R. Figure 2-1 shows a block diagram for the NI 7831R. Figure 2-2 shows the parts locator diagram for the NI PXI-7831R. Figure 2-3 shows the parts locator diagram for the NI PCI-7831R.
Chapter 2 Hardware Overview of the NI 7831R SW1 Figure 2-2. Parts Locator Diagram for the NI PXI-7831R NI 7831R User Manual 2-2 ni.
Chapter 2 Hardware Overview of the NI 7831R SW1 Figure 2-3. Parts Locator Diagram for the NI PCI-7831R Analog Input The NI 7831R has eight independent, 16-bit AI channels that you can sample simultaneously or at different rates. The input mode is software-configurable, and the input range is fixed at ±10 V. The converters return data in two’s complement format. Table 2-1 shows the ideal output code returned for a given AI voltage.
Chapter 2 Hardware Overview of the NI 7831R Table 2-1. Ideal Output Code and AI Voltage Mapping AI Voltage Output Code (Hex) (Two’s Complement) Full-scale range –1 LSB 9.999695 7FFF Full-scale range –2 LSB 9.999390 7FFE Midscale 0.000000 0000 Negative full-scale range +1 LSB –9.999695 8001 Negative full-scale range –10.000000 8000 Output Code ---------------------------------- × 10.
Chapter 2 Hardware Overview of the NI 7831R Connecting Analog Input Signals The AI signals for the NI 7831R are AI<0..7>+, AI<0..7>–, AIGND, and AISENSE. The AI<0..7>+ and AI<0..7>– signals are connected to the eight AI channels of the NI 7831R. For all input modes, the AI<0..7>+ signals are connected to the positive input of the instrumentation amplifier on each channel. The signal connected to the negative input of the instrumentation amplifier depends on how you configure the input mode of the device.
Chapter 2 Hardware Overview of the NI 7831R Vin+ + Instrumentation Amplifier + Vm – – Vin– Measured Voltage Vm = [Vin+ – Vin–] Figure 2-4. NI 7831R Instrumentation Amplifier The instrumentation amplifier applies common-mode voltage rejection and presents high input impedance to the AI signals connected to the NI 7831R. Input multiplexers on the device route signals to the positive and negative inputs of the instrumentation amplifier.
Chapter 2 Hardware Overview of the NI 7831R Types of Signal Sources When configuring the input channels and making signal connections, you must first determine whether the signal sources are floating or ground referenced. The following sections describe these two signal types. Floating Signal Sources A floating signal source is not connected to the building ground system but instead has an isolated ground-reference point.
Chapter 2 Hardware Overview of the NI 7831R Signal Source Type Input Floating Signal Source (Not Connected to Building Ground) Grounded Signal Source Examples • Ungrounded Thermocouples • Signal Conditioning with Isolated Outputs • Battery Devices Examples • Plug-in Instruments with Nonisolated Outputs AI(+) + V 1 – AI(–) + – AI(+) + V 1 – + AI(–) – Differential (DIFF) AIGND AIGND See text for information on bias resistors.
Chapter 2 Hardware Overview of the NI 7831R Differential Connection Considerations (DIFF Input Mode) In DIFF input mode, the NI 7831R measures the difference between the positive and negative inputs. DIFF input mode is ideal for measuring ground-referenced signals from other devices. When using DIFF input mode, the input signal connects to the positive input of the instrumentation amplifier and its reference signal, or return, connects to the negative input of the instrumentation amplifier.
Chapter 2 Hardware Overview of the NI 7831R GroundReferenced Signal Source + AI+ + AI– Instrumentation Amplifier Vs – – + Vm – CommonMode Noise and Ground Potential Measured Voltage + Vcm x8 Channels – AISENSE AIGND I/O Connector DIFF Input Mode Selected Figure 2-6.
Chapter 2 Floating Signal Source + Vs Bias Resistors (see text) Hardware Overview of the NI 7831R AI+ + AI– Instrumentation Amplifier – – + Vm – Bias Current Return Paths Measured Voltage x8 Channels AISENSE AIGND I/O Connector DIFF Input Mode Selected Figure 2-7. Differential Input Connections for Nonreferenced Signals Figure 2-7 shows two bias resistors connected in parallel with the signal leads of a floating signal source.
Chapter 2 Hardware Overview of the NI 7831R You can fully balance the signal path by connecting another resistor of the same value between the positive input and AIGND, as shown in Figure 2-7. This fully balanced input mode offers slightly better noise rejection but has the disadvantage of loading down the source with the series combination (sum) of the two resistors.
Chapter 2 Hardware Overview of the NI 7831R 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 differences in the signal path. Magnetic coupling is proportional to the area between the two signal conductors. Electrical coupling is a function of how much the electric field differs between the two conductors.
Chapter 2 Hardware Overview of the NI 7831R positive and negative inputs of the instrumentation amplifier. The instrumentation amplifier rejects this difference. If the input circuitry of a NI 7831R is referenced to ground in RSE input mode, this difference in ground potentials appears as an error in the measured voltage. Figure 2-9 shows how to connect a grounded signal source to a channel on the NI 7831R configured for NRSE input mode.
Chapter 2 Hardware Overview of the NI 7831R Analog Output The NI 7831R has eight 16-bit AO channels. The bipolar output range is fixed at ±10 V. Some applications require that the AO channels power on to known voltage levels. To set the power-on levels, you can configure the NI 7831R to load and run your VI when the system powers on. This VI can set the AO channels to the desired voltage levels. The VI interprets data written to the DAC in two’s complement format.
Chapter 2 Hardware Overview of the NI 7831R AO0 Channel 0 + Load VOUT 0 – AOGND0 x8 Channels NI 7831R Figure 2-10. Analog Output Connections Digital I/O The NI 7831R has 96 bidirectional DIO lines that you can individually configure for either input or output. When the system powers on, the DIO lines are high-impedance. To set another power-on state, you can configure the NI 7831R to load a VI when the system powers on. This VI can then set the DIO lines to any power-on state.
Chapter 2 Hardware Overview of the NI 7831R To interface to 5 V CMOS devices, you must provide an external pull-up resistor to 5 V. This resistor pulls up the 3.3 V digital output from the NI 7831R to 5 V CMOS logic levels. Refer to Appendix A, Specifications, for detailed DIO specifications. Exceeding the maximum input voltage ratings, listed in Table B-2, NI 7831R I/O Signal Summary, can damage the NI 7831R and the computer. NI is not liable for any damage resulting from such signal connections.
Chapter 2 Hardware Overview of the NI 7831R Figure 2-11 shows signal connections for three typical DIO applications. LED DGND +5 V TTL or LVCMOS* Compatible Devices DIO<4..7> 5 V CMOS† TTL, LVTTL, CMOS, or LVCMOS Signal DIO<0..3> +5 V Switch DGND I/O Connector NI 7831R *3.3 V CMOS †Use a pull-up resistor when driving 5 V CMOS devices. Figure 2-11. Example Digital I/O Connections Figure 2-11 shows DIO<0..3> configured for digital input and DIO<4..7> configured for digital output.
Chapter 2 Hardware Overview of the NI 7831R paired with power or ground. Because the DIO lines that are twisted with other DIO lines can couple noise onto each other, use these lines for static signals or non-edge-sensitive, low-frequency digital signals. 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 include LEDs, switches, and relays.
Chapter 2 Hardware Overview of the NI 7831R the remaining devices on that PXI bus segment must have PXI/TRIG0 configured as an input. Do not drive the same RTSI trigger bus line with the NI 7831R and another device simultaneously. Such signal driving can damage both devices. NI is not liable for any damage resulting from such signal driving. Caution For more information on using and configuring triggers, select Help»VI, Function, & How-To Help in LabVIEW to view the LabVIEW Help.
Chapter 2 Hardware Overview of the NI 7831R The left local bus lines from the left peripheral slot of a PXI backplane (Slot 2) are routed to the star trigger lines of up to 13 other peripheral slots in a two-segment PXI system. This configuration provides a dedicated, delay-matched trigger signal between the first peripheral slot and the other peripheral slots for precise trigger timing signals.
Chapter 2 Hardware Overview of the NI 7831R 4. Reinsert the NI 7831R into the PXI/CompactPCI chassis or PCI computer. Refer to the Installing the Hardware section of the Getting Started with the NI 7831R document for installation instructions. 5. Plug in and power on the PXI/CompactPCI chassis or PCI computer. After completing this procedure, a VI stored in flash memory does not load to the FPGA at power-on. You can use software to configure the NI 7831R if necessary.
Chapter 2 Hardware Overview of the NI 7831R Field Wiring Considerations Environmental noise can seriously affect the measurement accuracy of the device if you do not take proper care when running signal wires between signal sources and the device. The following recommendations mainly apply to AI signal routing to the device. They also apply to signal routing in general.
3 Calibration Calibration is the process of determining and/or adjusting the accuracy of an instrument to minimize measurement and output voltage errors. On the NI 7831R, onboard calibration DACs (CalDACs) correct these errors. Because the analog circuitry handles calibration, the data read from the AI channels or written to the AO channels in the FPGA VI is already calibrated. Three levels of calibration are available for the NI 7831R to ensure the accuracy of its analog circuitry.
Chapter 3 Calibration If you have NI-RIO installed, you can find the internal calibration utility at Start»All Programs»National Instruments»NI-RIO»device»Calibrate 7831R Device. Device is the NI PXI-7831R or NI PCI-7831R device. Immediately after internal calibration, the only significant residual calibration error is gain error due to time and temperature drift of the onboard voltage reference. You can minimize gain errors by performing an external calibration.
A Specifications This appendix lists the specifications of the NI 7831R. These specifications are typical at 25 °C unless otherwise noted. Analog Input Input Characteristics Number of channels ............................... 8 Input modes............................................ DIFF, RSE, NRSE (software-selectable; selection applies to all 8 channels) Type of ADC.......................................... Successive approximation Resolution ..............................................
Appendix A Specifications Overvoltage protection ...........................±42 V Data transfers ..........................................Interrupts, programmed I/O Accuracy Information Relative Accuracy Absolute Accuracy Nominal Range (V) Noise + Quantization (µV) % of Reading Positive Full Scale Negative Full Scale 24 Hours 10.0 –10.0 0.0496 1 Year Offset (µV) Single Point Averaged Temp Drift (%/°C) 0.0507 2542 1779 165 0.
Appendix A Specifications Settling Time Accuracy Step Size 16 LSB 4 LSB 2 LSB ±20.0 V 7.5 µs 10.3 µs 40 µs ±2.0 V 2.7 µs 4.1 µs 5.1 µs ±0.2 V 1.7 µs 2.9 µs 3.6 µs Crosstalk................................................. –80 dB, DC to 100 kHz Analog Output Output Characteristics Number of channels ............................... 8 single-ended, voltage output Resolution .............................................. 16 bits, 1 in 65,536 Update time .......................................
Appendix A Specifications DC Transfer Characteristics INL..........................................................±0.5 LSB typ, ±4.0 LSB max DNL ........................................................±0.5 LSB typ, ±1 LSB max Monotonicity ..........................................16 bits, guaranteed Voltage Output Range ......................................................±10 V Output coupling ......................................DC Output impedance...................................1.
Appendix A Specifications Digital logic levels Level Min Max Input low voltage (VIL) 0.0 V 0.8 V Input high voltage (VIH) 2.0 V 5.5 V Output low voltage (VOL), where IOUT = –Imax (sink) — 0.4 V Output high voltage (VOH), where IOUT = Imax (source) 2.4 V — Maximum output current Imax (source)..................................... 5.0 mA Imax (sink) ........................................ 5.0 mA Input leakage current.............................. ±10 µA Power-on state.........................
Appendix A Specifications Phase locked to PXI 10 MHz Clock(NI PXI-7831R only) ....................Adds 350 ps jitter, 300 ps skew Additional frequency dependent jitter 40 MHz............................................None 80 MHz............................................400 ps 120 MHz..........................................720 ps 160 MHz..........................................710 ps 200 MHz..........................................700 ps Calibration Recommended warm-up time.................
Appendix A Specifications by the digital outputs use the following equation: j ∑ current sourced on channel i i=1 Where j is the number of digital outputs being used to source current. Power available at I/O connectors ......... +4.50 to +5.25 VDC at 1 A total, 250 mA per I/O connector pin Physical Dimensions (not including connectors) NI PXI-7831R................................. 16 cm by 10 cm (6.3 in. by 3.9 in.) NI PCI-7831R ................................. 17 cm by 11 cm (6.7 in. by 4.3 in.
Appendix A Specifications chassis, tested in accordance with IEC-60068-2-1 and IEC-60068-2-2 Relative humidity range..........................10 to 90%, noncondensing, tested in accordance with IEC-60068-2-56 Altitude ...................................................2,000 m at 25 °C ambient temperature Storage Environment Ambient temperature range ....................–20 to 70 °C tested in accordance with IEC-60068-2-1 and IEC-60068-2-2 Relative humidity range..........................
Appendix A Specifications Safety This product is designed to meet the requirements of the following standards of safety for electrical equipment for measurement, control, and laboratory use: • IEC 61010-1, EN 61010-1 • UL 3111-1, UL 61010B-1 • CAN/CSA C22.2 No. 1010.1 Refer to the product label, or visit ni.com/hardref.nsf, search by model number or product line, and click the appropriate link in the Certification column for UL and other safety certifications.
B Connecting I/O Signals This appendix describes how to make input and output signal connections to the NI 7831R I/O connectors. The NI 7831R has two DIO connectors with 40 DIO lines per connector, and one MIO connector with eight AI lines, eight AO lines, and 16 DIO lines. Figure B-1 shows the I/O connector locations for the NI PXI-7831R and the NI PCI-7831R.
Appendix B Connecting I/O Signals Figure B-2 shows the I/O connector pin assignments for the I/O connectors on the NI 7831R. The DIO connector pin assignment applies to connectors <1..2> on the NI 7831R. The MIO connector pin assignment applies to connector 0 on the NI 7831R.
Appendix B Connecting I/O Signals . Table B-1. I/O Connector Signal Descriptions Signal Name Reference Direction Description +5V DGND Output +5 VDC Source—These pins supply 5 V from the computer power supply using a self-resetting 1 A fuse. No more than 250 mA should be pulled from a single pin. AI<0..7>+ AIGND Input Positive input for Analog Input channels 0 through 7. AI<0..7>– AIGND Input Negative input for Analog Input channels 0 through 7.
Appendix B Connecting I/O Signals Table B-2. NI 7831R I/O Signal Summary Signal Type and Direction Impedance Input/ Output Protection (Volts) On/Off Source (mA at V) Sink (mA at V) Rise Time Bias +5V DO — — — — — — AI<0..7>+ AI 10 GΩ in parallel with 100 pF 42/35 — — — ±2 nA AI<0..7>– AI 10 GΩ in parallel with 100 pF 42/35 — — — ±2 nA AIGND AO — — — — — — AISENSE AI 10 GΩ in parallel with 100 pF 42/35 — — — ±2 nA AO<0..7> AO 1.
Appendix B Connecting I/O Signals Connecting to 5B and SSR Signal Conditioning NI provides cables that allow you to connect signals from the NI 7831R directly to 5B backplanes for analog signal conditioning and SSR backplanes for digital signal conditioning. The NSC68-262650 cable connects the signals on the NI 7831R MIO connector directly to 5B and SSR backplanes. This cable has a 68-pin male VHDCI connector on one end that plugs into the NI 7831R MIO connector.
Appendix B Connecting I/O Signals AO0 AOGND0 AO1 AO2 AOGND2 AO3 AO4 AOGND4 AO5 AO6 AOGND6 AO7 NC 1 3 5 7 9 11 13 15 17 19 21 23 25 2 4 6 8 10 12 14 16 18 20 22 24 26 NC NC AOGND1 NC NC AOGND3 NC NC AOGND5 NC NC AOGND7 NC AO 0–7 Connector Pin Assignment AI0+ AIGND0 AI1+ AI2+ AIGND2 AI3+ AI4+ AIGND4 AI5+ AI6+ AIGND6 AI7+ AISENSE 1 3 5 7 9 11 13 15 17 19 21 23 25 2 4 6 8 10 12 14 16 18 20 22 24 26 AI0– AI1– AIGND1 AI2– AI3– AIGND3 AI4– AI5– AIGND5 AI6– AI7– AIGND7 NC AI 0–7 Connector Pin Assignment
Appendix B Connecting I/O Signals NSC68-5050 cable header. In this case, you have access only to the channels that exist on both the SSR backplane and the NSC68-5050 cable header you are using. Figure B-4 shows the connector pinouts when using the NSC68-5050 cable.
Using the SCB-68 Shielded Connector Block C This appendix describes how to connect input and output signals to the NI 7831R with the SCB-68 shielded connector block. The SCB-68 has 68 screw terminals for I/O signal connections. To use the SCB-68 with the NI 7831R, you must configure the SCB-68 as a general-purpose connector block. Refer to Figure C-1 for the general-purpose switch configuration. S5 S4 S3 S1 S2 Figure C-1.
Technical Support and Professional Services D Visit the following sections of the National Instruments Web site at ni.com for technical support and professional services: • Support—Online technical support resources at ni.
Appendix D Technical Support and Professional Services If you searched ni.com and could not find the answers you need, contact your local office or NI corporate headquarters. Phone numbers for our worldwide offices are listed at the front of this manual. You also can visit the Worldwide Offices section of ni.com/niglobal to access the branch office Web sites, which provide up-to-date contact information, support phone numbers, email addresses, and current events. NI 7831R User Manual D-2 ni.
Glossary Symbol Prefix Value p pico 10 –12 n nano 10 –9 µ micro 10 – 6 m milli 10 –3 k kilo 10 3 M mega 10 6 G giga 10 9 Numbers/Symbols ° Degrees. > Greater than. ≥ Greater than or equal to. < Less than. ≤ Less than or equal to. – Negative of, or minus. Ω Ohms. / Per. % Percent. ± Plus or minus. + Positive of, or plus.
Glossary Square root of. +5V +5 VDC source signal. A A Amperes. A/D Analog-to-digital. AC Alternating current. ADC Analog-to-digital converter—An electronic device, often an integrated circuit, that converts an analog voltage to a digital number. AI Analog input. AI Analog input channel signal. AIGND Analog input ground signal. AISENSE Analog input sense signal. AO Analog output. AO Analog output channel signal. AOGND Analog output ground signal.
Glossary C C Celsius. CalDAC Calibration DAC. CH Channel—Pin or wire lead to which you apply or from which you read the analog or digital signal. Analog signals can be single-ended or differential. For digital signals, you group channels to form ports. Ports usually consist of either four or eight digital channels. cm Centimeter. CMOS Complementary metal-oxide semiconductor.
Glossary DIO Digital input/output. DIO Digital input/output channel signal. DMA Direct memory access—A method by which data can be transferred to/from computer memory from/to a device or memory on the bus while the processor does something else. DMA is the fastest method of transferring data to/from computer memory. DNL Differential nonlinearity—A measure in LSB of the worst-case deviation of code widths from their ideal value of 1 LSB. DO Digital output.
Glossary 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. INL Relative accuracy. L LabVIEW Laboratory Virtual Instrument Engineering Workbench. LabVIEW is a graphical programming language that uses icons instead of lines of text to create programs. LSB Least significant bit. M m Meter. max Maximum. MIMO Multiple input, multiple output. min Minimum.
Glossary 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, electrical storms, welders, radio transmitters, and internal sources such as semiconductors, resistors, and capacitors. Noise corrupts signals you are trying to send or receive.
Glossary R RAM Random-access memory—The generic term for the read/write memory that is used in computers. RAM allows bits and bytes to be written to it as well as read from. Various types of RAM are DRAM, EDO RAM, SRAM, and VRAM. resolution The smallest signal increment that can be detected by a measurement system. Resolution can be expressed in bits, in proportions, or in percent of full scale. For example, a system has 12-bit resolution, one part in 4,096 resolution, and 0.0244% of full scale.
Glossary 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 created by joining two dissimilar metals. The junction produces a small voltage as a function of the temperature. TTL Transistor-transistor logic. two’s complement Given a number x expressed in base 2 with n digits to the left of the radix point, the (base 2) number 2n – x. V V Volts.
