1 Features of today's instruments
1.1 Hardware Function Softwareization With the development of microelectronic technology, the speed of microprocessors is getting faster and faster, and the price is getting lower and lower. It has been widely used in instruments and meters, making some real-time requirements very high. Originally completed by hardware. The functions can be realized by software. Even many problems that were difficult to solve or could not be solved with hardware circuits can be solved very well by software technology. The development of digital signal processing technology and the widespread adoption of high-speed digital signal processors have greatly enhanced the signal processing capabilities of the instrument. Digital filtering, FFT, correlation, and convolution are common methods of signal processing. Their common feature is that the main operations of the algorithm are composed of iterative multiplication and addition. If these operations are completed by software on a general-purpose computer, the calculation time is It is longer, and the digital signal processor completes the above multiplication and addition operations through hardware, which greatly improves the performance of the instrument and promotes the widespread application of digital signal processing technology in the field of instrumentation.
1.2 The development of integrated, modular large-scale integrated circuit LSI technology today, the density of integrated circuits is getting higher and higher, the volume is getting smaller and smaller, the internal structure is getting more and more complex, and the functions are getting more and more powerful. The degree of integration of each module and the entire instrument system. Modular function hardware is a powerful support for modern instruments, which makes the instrument more flexible and the instrument's hardware composition more concise. For example, when a certain test function needs to be added, only a small amount of modular function hardware needs to be added before calling Use the appropriate software to use this hardware.
1.3 Parameter setting and modification in real time With the development of various field programmable devices and on-line programming technologies, the parameters and even the structure of instruments need not be determined at the time of design, but can be placed and dynamically modified in the field where the instrument is used.
1.4 Generalization of the hardware platform Modern instruments and meters emphasize the role of software. One or several basic instrument hardware with common features are selected to form a general hardware platform, and various functions of instruments or systems can be expanded or composed by calling different software. An instrument can be roughly divided into three parts: 1) data collection; 2) data analysis and processing; 3) storage, display or output. Traditional instruments are built by manufacturers in a fixed manner according to the functions of the instruments. Generally, an instrument has only one or several functions. The modern instrument is a combination of general hardware modules with one or more of the above functions, and any kind of instrument is constituted by programming different software.
2 New methods of instrument design In order to create new characteristics of instrument development, various new design tools and design methods are constantly emerging. Here are the two representative ones to introduce.
2.1 The virtualized design of instrumentation and LabVIEW graphical development tools, a deeper combination of electronic instruments and computer technology has produced a new instrumentation model: Virtual Instrumentation. A virtual instrument refers to adding a layer of software and some hardware modules to a general-purpose computer, so that users can operate this general-purpose computer as if they were operating a specially designed instrument of their own. Virtual instrument technology emphasizes the role of software, and puts forward the concept of "software is an instrument". It is an emerging technology in the field of electronic testing and instrumentation, and is especially suitable for modern increasingly complex test systems.
NI's LabVIEW is a set of graphical programming software designed for data acquisition and instrument control, data analysis, and data expression. It enhances the ability of users to build their own instrumentation systems on standard computers with efficient and economical hardware equipment. By combining LabVIEW with general data acquisition and instrumentation equipment, virtual instruments can be designed and applied in many fields, unlike traditional instruments, which are limited by the functions designed by the manufacturer. LabVIEW provides a programming method like data flow. Users only need to connect various logic boxes to form programs. Its basic program unit is VI. LabVIEW uses graphic programming methods to build a series of VIs to complete user-specified test tasks. For simple test tasks, one VI can complete them; for complex test tasks, you can turn a complex test task into a series of subtasks according to the concept of module design. When designing, first design various VIs to complete each sub-task, and then combine these VIs to complete larger tasks. The top-level virtual instrument that is finally built becomes a collection of many sub-virtual instruments. There are many difficulties in developing instrument systems using traditional programming languages. Developers must not only care about program flow issues, but also must consider complex issues such as user interface, data synchronization, and data expression, all of which are easily solved in LabVIEW. LabVIEW also comes with several basic VI libraries. These include drivers for instruments using GP-IB, VISA, VXI, and serial interfaces. LabVIEW also has a powerful and huge analysis function library, which covers many scientific fields such as statistics, estimation, regression analysis, linear algebra, signal generation, time-domain frequency-domain analysis, and digital filtering.
2.2 ESP In System Programmability (ISP) In-System Programmability refers to the ability to program or repeatedly program the reconstructed logic device in the target system or circuit board designed by the user. This refactoring can be performed on-site or via the Internet during experimental development, manufacturing, or even after delivery to users. The application of ISP technology has brought revolutionary changes to the design of instrumentation instrumentation system. It makes the hardware system of the instrument no longer a fixed structure, but has the flexibility of the software. During the debugging process, the software function can be improved by continuously changing the "software". This new design concept of "soft" hardware Makes the system extremely adaptable.
Traditionally, system programmable technology is mainly used in digital system design. For example, FPGA field programmable gate arrays and CPLD complex programmable logic devices from Xilinx Corporation in the United States support ISP technology.
3 Conclusions Modern instruments are no longer single-function and fixed immutable structures, but are becoming more flexible and intelligent, more adaptable, and more feature-rich. Correspondingly, the design of instrumentation requires a broader knowledge and is therefore more challenging.