Computer-Based Instruments

Transcription

1 Computer-Based Instruments The Instrument is embedded in the PC The PC is embedded in the instrument

2 Computer-Based Instruments Scope Waveform Generator Multimeter Scope Oscilloscopio Waveform Gen Gen. di Funzioni Multimetro Multimeter

3 Automatic test equipment or automated test equipment (ATE) is any apparatus that performs tests on a device, known as the device under test (DUT), equipment under test (EUT) or unit under test (UUT), using automation to quickly perform measurements and evaluate the test results. An ATE can be a simple computer controlled digital multimeter or a complicated system containing dozens of complex test instruments (real or simulated electronic test equipment) capable of performing automatically tests and fault diagnosis.

4 Interface keyboard Instruments or SENSORS & SIGNALS Operating modes OFF-LINE: measurements are performed on the DUT when this is OFF. ON-LINE: measurements are performed on the DUT when this is working. REAL-TIME: measurements are performed very fast on the DUT during its operation.

5 Interface keyboard Instruments or Different scenaria Measurement of one quantity Measurement of multiple quantities by Data Acquisition Systems Measurements by instruments (IEEE 488.2) Distributed measurement systems

6 SOFTWARE DUT Different scenaria Measurement of one quantity Measurement of multiple quantities by Data Acquisition Systems Instrument BUS (GPIB, IEEE 488.1, 488.2) VME, VXI BUS

7 Measurement of one quantity Target quantity Sensor Electronics A/D CONVERTER CONTROL UNIT WIRINGS -A: depends on the nature of the target quantitiy. - B and C: are analog and must be as short as possible -D: is digital and no real restrictions on its lenght can be identified

8 SOFTWARE DUT Different scenaria Measurement of one quantity Measurement of multiple quantities by Data Acquisition Systems Instrument BUS (GPIB, IEEE 488.1, 488.2) VME, VXI BUS

9 Measurement of multiple quantities A/D CONV Control UNIT This scheme uses a ANALOG MULTIPLEXER The A/D converter must be shared among all channels, which will reduce the performance fo the system in terms of SAMPLING RATE.

10 Measurement of multiple quantities A/D CONV Control UNIT This scheme uses a ANALOG MULTIPLEXER and an ADPTIVE GAIN CONTROL

11 Measurement of multiple quantities Electronics Electronics Electronics Electronics A/D A/D A/D A/D D I G I T A L M U L T I P L E X E R Control UNIT This scheme uses a DIGITAL MULTIPLEXER One A/D converter is used per each channel, which will improve the system performances in term of Sampling Rate at the expense of an high cost.

12 Measurement of multiple quantities Measurement schemes above presented are implemented through a:

13 Data acquisition (DAQ) is the process of measuring an electrical or physical phenomenon such as voltage, current, temperature, pressure, or sound with a computer. Definitions by:

14 A DAQ system consists of: -Sensors -DAQ measurement hardware -a computer with programmable software. Definitions by:

15 Compared to traditional measurement systems, PCbased DAQ systems exploit: -the processing power; -Productivity; - display: - connectivity capabilities of industry-standard computers Definitions by:

16 -More powerful; - Flexible; - Cost-effective measurement solution. Definitions by:

17 Management and Control System DAQ Plants

18 Management and control system RX and TX Data DAQ Storing Info Extraction Digital processing A/D Conversion Signal processing Actuation control Signal Conditioning SENSORS Actuators PLANT

19 Signal Conditioning Amplification Amplifiers boost the level of the input signal to better match the range of the analog-todigital converter (ADC), thus increasing the resolution and sensitivity of the measurement. Using external signal conditioners located closer to the signal source, or transducer, improves the signal-tonoise ratio of the measurement by boosting the signal level before it is affected by environmental noise. Attenuation Attenuation is the opposite of amplification. It is necessary when the voltages to be digitized are beyond the input range of the digitizer.

20 Signal Conditioning Filtering Signal conditioners can include filters to reject unwanted noise within a certain frequency range. Almost all DAQ applications are subject to some level of 50 or 60 Hz noise picked up from power lines or machinery. Therefore, most conditioners include lowpass filters designed specifically to provide maximum rejection of 50 to 60 Hz noise. Another common use of filters is to prevent signal aliasing a phenomenon that arises when a signal is undersampled (sampled too slowly). You can avoid this signal distortion only by removing any signal components above one-half the sampling frequency with low-pass filters before the signal is sampled.

21 Signal Conditioning Isolation Improper grounding of the system is one of the most common causes for measurement problems, including noise and damaged measurement devices. Signal conditioners with isolation can prevent most of these problems. Such devices pass the signal from its source to the measurement device without a physical connection by using transformer, optical, or capacitive coupling techniques. Multiplexing Typically, the digitizer is the most expensive part of a data acquisition system. By multiplexing, you can sequentially route a number of signals into a single digitizer, thus achieving a cost-effective way to greatly expand the signal count of your system. Multiplexing is necessary for any high-channelcount application. Simultaneous Sampling When it is critical to measure two or more signals at the same instant in time, simultaneous sampling is required.

22 Management and control system RX and TX Data DAQ Storing Info Extraction Digital processing A/D Conversion Signal processing Actuation control Signal Conditioning SENSORS Actuators PLANT

23 A/D Conversion

24 A/D Conversion Advantages of operating with Digital Signals: - High noise rejection - Easily to be elaborated by PC or embedded architectures (Microcontroller based) - Easily to be trasmitted and stored

25 A/D Conversion [V] samples Sampling (in the time domain) A right sampling rate must be choosen in order to assure a reliable rapresentation of the analog signal in the digital domain Quantization (in the amplitude domain) The sample is then converted into a digital code (e.g. 0010)

26 A/D Conversion The sampling Theorem: In case of a signal f(t) with a Fourier Trasnform F( ): F( )=0 for >= c (band limited) The signal f(t) is completely determined by giving its ordinates at a series of points (samples) spaced 1/(2 c ) seconds apart. A sufficient sample-rate, s is therefore 2 c samples/second, or anything larger. f t f nt s 2 ; c sin T c c t t 2 / nt s nt

27 Amplitude Amplitude Amplitude Automatic TEST Equipment A/D Conversion s 10 c Time s 3 c s 10 c Time Time

28 SCXI-1001 VXI PCI, ISA Workstation PCMCIA Desktop Notebook Software runs unmodified on each platform!

29 DAQ board+pc

30 DAQ board+pc PC/XT PS/2 PC AT PCMCIA Macintosh NuBus EISA SBus

31 DAQ board+pc

32 DAQ board

33 DAQ board DAQ E-Series National Instruments

34 DAQ board E Series by National Instruments RTSI NI-PGIA DAQ-STC DAQ-PnP

35 DAQ board Input blocks Multiplexer, Amplifiers, A/D Converters D/A Converters I/O and Timer

36 Signals to DAQ connection Different scenaria can appear when we have to connect a signal source to a DAQ device: The device input and the signal source have the same (or common) ground. The device input and the signal source have an offset voltage between their grounds (AC and/or DC). This offset is the common mode voltage. The device and the signal source already have isolated grounds.

37 Signals to DAQ connection The device input and the signal source have the same (or common) ground. CONNECTION Common ground / single-ended inputs Single-ended is the recommended configuration for common ground connections.

38 Signals to DAQ connection The device input and the signal source have the same (or common) ground. CONNECTION Common ground / differential inputs Using differential inputs to monitor a signal source with a common ground is acceptable, though it requires more wiring and offers fewer channels than selecting a single-ended configuration.

39 Signals to DAQ connection The device input and the signal source have an offset voltage between their grounds (AC and/or DC). This offset is the common mode voltage. CONNECTION Common mode voltage / differential inputs Systems with varying ground potentials should always be monitored in the differential mode.

40 Signals to DAQ connection The device and the signal source already have isolated grounds. CONNECTION Isolated grounds / single-ended inputs Single-ended inputs can be used to monitor isolated inputs, although using differential mode increases your system s noise immunity.

41 Signals to DAQ connection The device and the signal source already have isolated grounds. CONNECTION Isolated grounds / differential inputs To ensure optimum performance with isolated signal sources, use the differential input setting.

42 DAQ BOARD SPECIFICATIONS Number and kind of channels RTD, SG, Thermocouples, Analog/Digital I/O Sampling frequency Sampling mode: multiplexed or simultaneous; Resolution: A/D bit; Span NLD Error Settling time Noise; AO channels; Digital I/O; Timing

43 T e m p e r a t u r e F l o w C o n t r o l P a n e l Automatic TEST Equipment P r e s s u r e A l a r m C o n d i t i o n s S T O P FieldPoint FieldPoint is a distributed measurement system for monitoring or controlling signals in light industrial applications. A FieldPoint system includes a serial or Ethernet network module and up to nine I/O modules in a bank. Each I/O module can measure eight or 16 channels. FieldPoint is for applications with small clusters of I/O points at several different locations. FieldPoint is also an attractive solution for costsensitive applications performing low-speed monitoring.

44 Compact RIO The CompactRIO platform is an advanced embedded data acquisition and control system designed for applications that require both high performance and reliability. The CompactRIO systems consist of: -an embedded controller for communication and processing, -a reconfigurable chassis housing the userprogrammable FPGA, - hot-swappable I/O modules - graphical LabVIEW software for rapid real-time, Windows, and FPGA programming.

45 Compact RIO CompactRIO controller The CompactRIO controller includes a processor and reconfigurable FPGA. The processor is used for network communication, data logging, control, and processing with the deterministic and reliable NI Linux Real-Time OS. With the user-programmable FPGA, you can implement custom hardware for high-speed control, inline data processing, or complex timing and triggering.

46 Compact RIO MXI-Express RIO Expansion Chassis NI MXI-Express RIO chassis deliver the highestperformance expansion RIO solution for applications that require custom signal processing and control algorithms and mixed-signal conditioned I/O. Featuring high-throughput and best-in-class FPGAs, these chassis are ideal for hardware-in-theloop, real-time test and complex research applications. These chassis feature eight or 14 C Series I/O slots. With 250 MB/s bus throughput, MXI-Express RIO can handle the most intense data streaming applications.

47 Compact RIO Ethernet RIO Expansion Chassis NI Ethernet RIO chassis offer the most flexible RIO expansion solution by making it easy to add a userprogrammable FPGA and mixed-signal conditioned I/O to any Ethernet network. These chassis are ideal for distributed, remote measurement systems and can integrate easily with any real-time CompactRIO system, real-time PXI system, or Windows PC using standard 10/100 Ethernet. Ethernet RIO chassis feature four or eight C Series I/O slots each; an integrated user-programmable FPGA for custom timing, inline processing, and control; a network fail-safe for increased reliability; and support for the LabVIEW FPGA Module and RIO Scan Mode.

48 Compact RIO Wireless Sensor Network With the NI wireless sensor network (WSN) product family, you can easily monitor your assets or environment with reliable, batterypowered measurement nodes that offer industrial ratings and local analysis and control capabilities. Each wireless network can scale from tens to hundreds of nodes and seamlessly integrate with existing CompactRIO systems.

49 Compact RIO C Series I/O Modules C Series modules from National Instruments are compact measurement and I/O devices that combine connectivity, signal conditioning, and A/D conversion for direct connection to a wide range of sensors to cover both dynamic acquisition and static monitoring requirements. Low-noise designs, 24-bit A/D technology with built-in antialiasing filters, high-speed A/D conversion rates, and electrical isolation ensure that sensor data is acquired reliably and accurately. Examples: strain gages, accelerometers, displacement sensors, and a variety of environmental sensors

50 SCXI An SCXI system consists of a rugged chassis that houses shielded signal conditioning modules that amplify, filter, isolate, and multiplex analog signals from thermocouples or other transducers. SCXI is designed for large measurement systems or systems requiring high-speed acquisition. System features include: Modular architecture choose your measurement technology Expandability expand your system to 3,072 channels Integration combine analog input, analog output, digital I/O, and switching into a single, unified platform High bandwidth

51 Model Description AO Analog Input Digital Automatic TEST Equipment : SCXI SCXI channel AI multiplexer SCXI channel thermocouple amplifier SCXI channel isolation amplifier input SCXI ch. isolation amplifier with excitation SCXI channel isolated multiplexer SCXI channel simultaneous sample-and- hold SCXI channel lowpass (antialiasing) filter SCXI channel analog out (V or I) SCXI-1160/61 8/16-channel electromech.. relays SCXI-1162/62HV 32-channel digital input SCXI channel digital output SCXI-1163R 32-channel solid-state relays

52 PXI PXI is a rugged PC-based platform for measurement and automation systems. PXI combines PCI electrical-bus features with the modular, Eurocard packaging of CompactPCI and then adds specialized synchronization buses and key software features. PXI is both a high-performance and low-cost deployment platform for applications such as manufacturing test, military and aerospace, machine monitoring, automotive, and industrial test.

53 PXI-CHASSIS PCI and PCI Express Communication The PXI chassis provides the communication buses of PCI and PCI Express for controller and modules. The PCI bus uses a shared bus topology where the theoretical 132 MB/s peak bandwidth is divided among multiple devices so the different devices on the bus can communicate. PCI Express provides a point-to-point bus topology, replacing the shared bus with a shared switch. This gives each device its own direct access to the bus, and thus its own dedicated data pipelines called lanes. You can group these lanes together to increase bandwidth to the slot to achieve up to 24 GB/s of throughput.

54 PXI-CHASSIS Timing and Synchronization PXI builds on its CompactPCI architecture base by adding integrated timing and synchronization that is used to route synchronization clocks and triggers internally. A PXI chassis incorporates a dedicated 10 MHz system reference clock, PXI trigger bus, star trigger bus, and slot-to-slot local bus, while a PXI Express chassis adds a 100 MHz differential system clock, differential signaling, and differential star triggers to address the need for advanced timing and synchronization.

55 PXI Embedded Controllers With embedded controllers, there s no need for an external PC. You have a complete system contained within the PXI chassis. Embedded controllers include standard features such as an integrated (multicore) CPU, hard drive, memory, Ethernet, video, serial, USB, and other peripherals. They are available for systems based on PXI or PXI Express, and you have your choice of OSs, including Windows or LabVIEW Real-Time.

56 PXI MODULES Module Types To meet your test or embedded application needs, you can choose from more than 450 NI modules including the following: CAN Controller area network (CAN) interfaces meet the physical and electrical requirements for in-vehicle automotive networks based on CAN. Counter/Timers These modules provide a variety of counting and timing measurements, including measuring a number of time-related quantities, counting events, or totalizing and measuring position with quadrature encoders. Digital I/O With voltage levels up to 150 V, high current drive, and isolation, industrial digital I/O can connect directly to a wide array of pumps, valves, motors, and other sensors/actuators. Digital Multimeters and LCR Meters Optimized for automated test, these devices accurately measure voltage, resistance, current, capacitance, inductance, and temperature.

57 PXI MODULES Module Types Digitizers/Oscilloscopes These devices feature unmatched versatility for both time and frequency domain applications. Along with standard oscilloscope measurements, you can use them as spectrum analyzers, transient recorders, ultrasonic receivers, and a multitude of other instruments. Dynamic Signal Analyzers (DSAs) DSAs are designed specifically for applications requiring audio, noise, and vibration measurements. FlexRay FlexRay interfaces meet the physical and electrical requirements for in-vehicle automotive networks based on FlexRay, including support for both cold-start and normal applications. Frame Grabbers Frame grabbers acquire images from Camera Link, GigE Vision, IEEE 1394, and analog and parallel digital devices. GPIB Connect to rack-and-stack instrumentation using the industry s most popular instrument control standard.

58 PXI MODULES Module Types High-Speed Digital I/O Meet application challenges from custom digital communication analysis to end-of-line functional testing. Industrial Network Interfaces Handle remote measurement, industrial control, and data logging for a diverse set of sensors and actuators regardless of the environment or distance. Local Interconnect Network (LIN) These interfaces are for the low-cost, low-end multiplexed communication LIN bus standard in automotive networks. Motion Control You can use these modules for a variety of applications, ranging from simple single-axis control to distributed, synchronized multi-axis control. Multifunction Data Acquisition These devices offer analog I/O, digital I/O, and counter/timer circuitry. Ranging from low cost to high performance, they provide great value and ease of use.

59 PXI MODULES Module Types NI FlexRIO Custom Instruments These high-performance, reconfigurable instruments are powered by the NI LabVIEW FPGA Module. Solutions consist of NI FlexRIO FPGA Modules for PXI and adapter modules to add I/O to the field-programmable gate array (FPGA). Power Supplies and Source Measure Units (SMUs) These devices include high-channel-count, high-speed SMUs; precision SMUs; high-power SMUs; general-purpose power supplies; and fast transient power supplies. RF These fast, flexible, and accurate RF instruments up to 26.5 GHz include RF signal generators, analyzers, and vector network analyzers. Serial One- to 16-port interfaces to RS232 and RS485 standards.

60 PXI MODULES Module Types Signal Conditioning Data acquisition is integrated with signal conditioning on a single PXI card to achieve the best accuracy and throughput for strain gages, bridge-based transducers, temperature, and high-voltage analog input signals. Signal Generators These devices include versatile arbitrary waveform generators, function generators, and clock and frequency generators. Switches This extensive line features matrix switches and multiplexers to general-purpose switches, RF switches, and relays. Timing and Synchronization These modules use and drive the trigger bus, star trigger, and system reference clock features of PXI to implement advanced multidevice synchronization.

61 DUT Different scenaria Measurement of one quantity Measurement of multiple quantities by Data Acquisition Systems Instrument BUS (GPIB, IEEE 488.1, 488.2) VME, VXI BUS

62 Measurement BUS Device 1 Device 2 Device 3 Controller Device 6 Device 5 Device 4 Star Bus Controller Device 1 Device 2 Device 5 Device 4 Device 3 Daisy chain Device 1 Device 2 Device 3 Controller Device 6 Device 5 Device 4 Party Line

63 Measurement BUS GPIB The General Purpose Interface Bus (GPIB) is a system of hardware and software that allows you to control test equipment to make measurements quickly and accurately.

64 Measurement BUS GPIB Origin of GPIB The original GPIB was developed in the late 1960s by Hewlett-Packard (where it is called the HP-IB) to connect and control programmable instruments that Hewlett- Packard manufactured. In 1975, the Institute of Electrical and Electronic Engineers (IEEE) published ANSI/IEEE Standard , IEEE Standard Digital Interface for Programmable Instrumentation, which contained the electrical, mechanical, and functional specifications of an interfacing system. The original IEEE was revised in 1978, primarily for editorial clarification and addendum. This bus is now used worldwide and is known by three names: General Purpose Interface Bus (GPIB) Hewlett-Packard Interface Bus (HP-IB) IEEE 488 Bus

65 Measurement BUS GPIB Origin of GPIB Because the original IEEE 488 document contained no guidelines for a preferred syntax and format conventions, work continued on the specification to enhance system compatibility and configurability among test systems. This work resulted in a supplement standard, IEEE 488.2, Codes, Formats, Protocols, and Common Commands, for use with IEEE 488 (which was renamed IEEE 488.1). IEEE does not replace IEEE IEEE builds on IEEE by defining a minimum set of device interface capabilities, a common set of data codes and formats, a device message protocol, a generic set of commonly needed device commands, and a new status reporting model. In 1990, the IEEE specification included the Standard Commands for Programmable Instrumentation (SCPI) document, which defines specific commands that each instrument class (which usually includes instruments from various vendors) must obey. SCPI guarantees complete system compatibility and configurability among instruments. It is no longer necessary to learn a different command set for each instrument in an SCPI-compliant system, and it is easy to replace an instrument from one vendor with an instrument from another.

66 Measurement BUS GPIB

67 Measurement BUS GPIB Cables GPIB Cables are the physical link connecting all of the devices on the bus. There are: eight data lines in a GPIB cable that send data from one device to another. eight control lines that manage traffic on the data lines and control other interface operations. Maximum data rate - 1 megabyte per second over limited distances, 250 to 500 kilobytes per second typical maximum over a full transmission path. Limitations: - Do not connect more than 15 devices on any GPIB system. - Do not exceed a total of 20 meters of total cable length or 2 meters per device, whichever is less. - Avoid stacking more than three connectors on the back panel of an instrument. This can cause unnecessary strain on the rear-panel connector.

68 Measurement BUS GPIB Every GPIB instrument must have its own unique address on the bus. Each device can assume one of the following roles: Talkers are instruments that can be addressed to send data to the controller. Listeners are instruments that can be addressed to receive a command, and then respond to the command. All devices on the bus are required to listen. Controllers Controllers specify the instruments that will be the talker and listener in a data exchange. The controller of the bus must have a GPIB interface card to communicate on the GPIB. - The Active Controller is the computer or instrument that is currently controlling data exchanges. - The System Controller is the only computer or instrument that can take control and give up control of the GPIB to another computer or instrument, which is then called the active controller.

69 Measurement BUS GPIB The GPIB / SCPI Programming Elements The following software programming elements combine to become a GPIB program: GPIB / SCPI Commands Programming Statements Instrument Drivers GPIB Commands The GPIB command is the basic unit of communication in a GPIB system. The analyzer responds to GPIB commands: 1. IEEE Bus-management Commands These commands are used primarily to tell some or all of the devices on the bus to perform certain interface operations. Examples of IEEE Commands CLEAR - Clears the bus of any pending operations LOCAL - Returns instruments to local operation

70 Measurement BUS GPIB The GPIB / SCPI Programming Elements The following software programming elements combine to become a GPIB program: GPIB / SCPI Commands Programming Statements Instrument Drivers GPIB Commands The GPIB command is the basic unit of communication in a GPIB system. The analyzer responds to three types of GPIB commands: 1. IEEE Bus-management Commands These commands are used primarily to tell some or all of the devices on the bus to perform certain interface operations. Example: CLEAR - Clears the bus of any pending operations LOCAL - Returns instruments to local operation 2. IEEE Common Commands These commands are sent to instruments to perform interface operations.

71 Measurement BUS GPIB The GPIB / SCPI Programming Elements The following software programming elements combine to become a GPIB program: GPIB / SCPI Commands Programming Statements Instrument Drivers GPIB Commands The GPIB command is the basic unit of communication in a GPIB system. The analyzer responds to three types of GPIB commands: 3. SCPI Commands The Standard Commands for Programmable Instruments (SCPI) is a set of commands developed in The standardization provided in SCPI commands helps ensure that programs written for a particular SCPI instrument are easily adapted to work with a similar SCPI instrument. SCPI commands tell instruments to do device specific functions. For example, SCPI commands could tell an instrument to make a measurement and output data to a controller.

72 SCPI Commands Measurement BUS GPIB An example to generate a waveform by the waveform generator: APPLy :SINusoid [<frequency> [,<amplitude> [,<offset>] ]] :SQUare [<frequency> [,<amplitude> [,<offset>] ]] :TRIangle [<frequency> [,<amplitude> [,<offset>] ]] :RAMP [<frequency> [,<amplitude> [,<offset>] ]] :NOISe [<frequency DEF> [,<amplitude> [,<offset>] ]] :DC [<frequency DEF> [,<amplitude DEF> [,<offset>] ]] :USER [<frequency> [,<amplitude> [,<offset>] ]] APPLy? "APPL:SIN 5 KHZ, 3.0 VPP, -2.5 V"

73 Measurement BUS GPIB The GPIB / SCPI Programming Elements The following software programming elements combine to become a GPIB program: GPIB / SCPI Commands Programming Statements Instrument Drivers Programming Statements SCPI commands are included with the language specific I/O statements to form program statements. SCPI programs can be written in a variety of programming languages Example of a Visual Basic statement: GPIB.Write "SOURCE:FREQUENCY:FIXED 1000 MHz Instrument drivers Subroutines that provide routine functionality and can be reused from program to program.

74 DUT Different scenaria Measurement of one quantity Measurement of multiple quantities by Data Acquisition Systems Instrument BUS (GPIB, IEEE 488.1, 488.2) VME, VXI BUS

75 Measurement BUS: VME/VXI VME is a high speed and high performance bus system with powerful interrupt management and multiprocessor capability. It was created by combining VERSAbus electrical specifications (1979) with the Eurocard format resulting in the VMEbus Revision A specification. The VMEbus specification has since then been refined through revisons B (1982), C, C.1, IEC 821 & IEC297 and IEEE VME represents one of today's most used industry bus standards (see VMEbus International Trade Association - VITA).

76 Measurement BUS: VME/VXI VME Bus Description Address Lines The VME bus has 31 address lines. Data Lines The VME bus has 32 data lines. Bus Arbitration A VME Bus master requests the bus by asserting one of the bus request lines BR0*- BR3*

77 Measurement BUS: VME/VXI VXI Standard (IEEE 1155) VXI is a open standard platform for automated test instruments based upon VMEbus, the Eurocard standards, and other instrumentation standards such as IEEE VXI's core market is in Telecommunication, Military and Aerospace automatic test systems and data acquisition applications.

78 Measurement BUS: VME/VXI VXI Standard (IEEE 1155) VXI is Based on VME bus protocol for data transfers between modules VXI implements a number of significant enhancements towards data acquisition and automated test applications. Especially the VXI mechanical and power supply specifications provide an excellent electrical environment for low-level, high accuracy analog circuitry.

79 Measurement BUS: VME/VXI VXI Standard (IEEE 1155) Fully shielded mechanical design of modules to minimize noise pickup and provides more front panel space, Mandatory analog power supply voltages (- 5.2V, -2V, +/-24V) and strict limits for power supply noise Specifications for cooling and measurement of cooling performance (VXI-8) to allow use of high power electronic circuits in VXI modules. VXI Backplane provides precision clocks and trigger lines for common clocking and triggering /event handling across VXI modules Local bus for inter-module communication Power-up self test (status register bit indicates whether the module passed self-test or not).

80 Measurement BUS: VME/VXI VXI Standard (IEEE 1155) A VXI bus system can have up to 256 devices, including one or more VXI bus subsystems. A VXI bus subsystem consists of a central timing /controller module in Slot 0 (Slot-0 controller) with up to twelve additional instrument modules. The Slot 0 module is responsible for managing system resources such as the VXI bus mandated timing generation, the VME bus system controller functions and a possible data communication ports such as Ethernet, RS232 or IEEE 488. A typical VXI crate has 13 slots The VXI crate provides power for the following DC voltages: +5V, +/-12V (as per VME spec.), -5.2V, -2V (for ECL devices / termination), +/-24V (for analog circuits)

81 Measurement BUS

82 Measurement BUS

83 SOFTWARE DUT Different scenaria Measurement of one quantity Measurement of multiple quantities by Data Acquisition Systems Instrument BUS (GPIB, IEEE 488.1, 488.2) VME, VXI BUS

84 Programming - Communication bus/interface driver - Instrument driver; - Measurement procedure (program); - Application program

85 APPLICATION SOFTWARE LabVIEW LabVIEW is a program development application, much like various commercial C or BASIC development systems, or National Instruments LabWindows. However, LabVIEW is different from those applications in one important respect. Other programming systems use text-based languages to create lines of code, while LabVIEW uses a graphical programming language, G, to create programs in block diagram form. You can use LabVIEW with little programming experience. LabVIEW uses terminology, icons, and ideas familiar to scientists and engineers and relies on graphical symbols rather than textual language to describe programming actions. LabVIEW has extensive libraries of functions and subroutines for most programming tasks. For Windows, Macintosh, and Sun, LabVIEW contains application specific libraries for data acquisition and VXI instrument control. LabVIEW also contains application-specific libraries for GPIB and serial instrument control, data analysis, data presentation, and data storage. LabVIEW includes conventional program development tools, so you can set breakpoints, animate program execution to see how data passes through the program, and single-step through the program to make debugging and program development easier.