Data processing: measuring – calibrating – or testing – Calibration or correction system – Error due to component compatibility
Reexamination Certificate
1998-08-21
2002-06-11
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Error due to component compatibility
C702S121000
Reexamination Certificate
active
06405145
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to instrument driver software for instrumentation systems, and more particularly to an instrumentation driver software architecture for communicating with and controlling instruments in an instrumentation system.
DESCRIPTION OF THE RALATED ART
An instrument is a device which collects data or information from an environment or unit under test and displays this information to a user. An instrument may also perform various data analysis and data processing on acquired data prior to displaying the data to the user. Examples of various types of instruments include oscilloscopes, digital multimeters, pressure sensors, etc., and the types of information which might be collected by respective instruments include voltage, resistance, distance, velocity, pressure, frequency of oscillation, humidity or temperature, among others.
In the past, many instrumentation systems comprised individual instruments physically interconnected with each other. Each instrument typically included a physical front panel with its own peculiar combination of indicators, knobs, or switches. A user generally had to understand and manipulate individual controls for each instrument and record readings from an array of indicators. Acquisition and analysis of data in such instrumentation systems was tedious and error prone.
A significant advance occurred with the introduction of computers to provide more flexible means for interfacing instruments with a user. In such computerized instrumentation systems, the user interacts with software executing on the computer system through the computer's video monitor rather than through a manually operated front panel to control one or more real world instruments. The software executing on the computer system can be used to simulate the operation of an instrument in software or to control or communicate with one or more real world instruments, these software created/controlled instruments being referred to as virtual instruments.
Therefore, modern instrumentation systems are moving from dedicated stand-alone hardware instruments such as oscilloscopes, digital multimeters, etc., to a concept referred to as virtual instrumentation. Virtual instrumentation comprises general purpose personal computers and workstations combined with instrumentation software and hardware to build a complete instrumentation system. In a virtual instrumentation system, a virtual instrument operating on a central computer controls the constituent instruments from which it acquires data which it analyzes, stores, and presents to a user of the system. Computer control of instrumentation has become increasingly desirable in view of the increasing complexity and variety of instruments available for use, and computerized instrumentation systems provide significant performance efficiencies over earlier systems for linking and controlling test instruments.
The various hardware interface options currently available for instrumentation systems can be categorized into various types, including IEEE 488-controlled instruments (GPIB instruments), VXI bus instruments, plug-in data acquisition (DAQ) boards, PCI bus and PXI bus instruments, and serial instruments, such as RS-232-controlled, USB, or IEEE 1394 instruments, among others. Background on these various hardware interface options is deemed appropriate.
The GPIB (general purpose interface bus) began as a bus designed by Hewlett-Packard in 1965, referred to as the Hewlett-Packard Interface Bus (HPIB), to connect their line of programmable instruments to their computers. National Instruments Corporation expanded the use of this bus to computers manufactured by companies other than Hewlett-Packard and hence the name General Purpose Interface Bus (GPIB) became more widely used than HPIB. The GPIB interface bus gained popularity due to its high transfer rates and was later accepted as IEEE standard 488-1975, and the bus later evolved to ANSI/IEEE standard 488.1-1987. In order to improve on this standard, two new standards were drafted, these being ANSI/IEEE 488.2-1987 and the SCPI (Standard Commands for Programmable Instruments) standard. The IEEE 488.2 standard strengthened the original standard by defining precisely how controllers and instruments communicated. The IEEE 488.2 standard removed ambiguities of the IEEE 488.1 standard by defining data formats, status reporting, a message exchange protocol, IEEE 488.2 controller requirements, and common configuration commands to which all IEEE 488.2 instruments must respond in a precise manner. Thus, the IEEE 488.2 standard created more compatible, more reliable systems that were simpler to program. In 1990, a new specification was developed referred to as the Standard Commands for Programmable Instruments (SCPI), which used the command structures defined in the IEEE 488.2 standard and formed a single, comprehensive programming command set that is used with any SCPI instrument. The SCPI standard simplified the programming process for manufacturers and users alike. Rather than having to learn a different command set for each instrument, the user could focus on solving the measurement tests of his or her application, thus decreasing programming time.
The VXI (VME eXtension for Instrumentation) bus is a platform for instrumentation systems that was first introduced in 1987 and was originally designed as an extension of the VME bus standard. The VXI standard has experienced tremendous growth and acceptance around the world and is used in a wide variety of traditional test and measurement and ATE applications. The VXI standard uses a mainframe chassis with a plurality of slots to hold modular instruments on plug-in boards. The VXI architecture is capable of interfacing with both message-based instruments and register-based instruments. A message-based instrument is an instrument which is controlled by a string of ASCII characters, whereas a register-based instrument is controlled by writing a bit stream of 1's and 0's directly to registers in the instrument hardware.
An instrumentation system using a data acquisition interface method typically includes transducers which sense physical phenomena from the process or unit under test and provide electrical signals to data acquisition hardware inside the computer system. The electrical signals generated by the transducers are converted into a form that the data acquisition board can accept, typically by signal conditioning logic positioned between the transducers and the data acquisition card in the computer system.
PCI (Peripheral Component Interconnect) bus instruments and PXI (PCI eXtensions for Instrumentation) instruments leverage off of the PCI bus found in mainstream computer systems. These instruments include a connector which is electrically compatible with the PCI bus. “Desktop PCI” instruments have a conventional PCI form factor for use in desktop PCs. The PXI instrumentation bus standard, promulgated by National Instruments, includes a CompactPCI mechanical form factor, is electrically compatible with the PCI bus, and includes extra signal definitions for instrumentation purposes.
A computer can also control an instrumentation system through a serial connection, such as the computer's serial or RS-232 port, the USB (Universal Serial Bus), or the IEE 1394 or 1394.2 bus, referred to as Firewire. There are currently thousands of instruments with an RS-232 interface.
Due to the wide variety of possible testing situations and environments, and also the wide array of instruments available, it is often necessary for a user to develop a program to control respective instruments in the desired instrumentation system. Therefore, implementation of such systems frequently requires the involvement of a programmer to develop software for acquisition, analysis and presentation of instrumentation data.
The software architecture for an instrumentation system, such as a virtual instrumentation system, comprises several components. The top level of the software architecture typically comprises an application pr
Bellin Jon
Grey James
Rust Scott
Conley Rose & Tayon PC
Hood Jeffrey C.
Miller Craig Steven
National Instruments Corporation
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