Function principle and development trend of the ho

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The emergence of intelligent instruments has greatly expanded the application scope of traditional instruments. With its advantages of small size, strong function and low power consumption, intelligent instruments have been widely used in household appliances, scientific research institutions and industrial enterprises

1. Working principle of intelligent instrument

the sensor picks up the information of the measured parameters and converts it into electrical signals, which are sent to the multi-channel analog switch after filtering and removing the interference; The signals of each input channel are sent to the program-controlled gain amplifier one by one by selecting the analog switch one by one by the single-chip microcomputer. The amplified signal is converted into the corresponding pulse signal by the A/D converter and then sent to the single-chip microcomputer; According to the initial value set by the instrument, the single chip microcomputer performs the corresponding data operation and processing (such as nonlinear correction, etc.); The result of the operation is converted into corresponding data for display and printing; At the same time, the single-chip microcomputer compares the operation results with the set parameters stored in the on-chip flashrom (flash memory) or e  2PROM (electrically erasable memory), and outputs the corresponding control signals (such as alarm device trigger, relay contact, etc.) according to the operation results and control requirements. In addition, the intelligent instrument can also form a distributed measurement and control system with PC. the single-chip microcomputer refers to that the metal sheet at the top of the experimental machine is the lower computer to collect the measurement signals and data of various tension machines equipped with 3-wire power plugs, and transmit the information to the upper computer - PC through serial communication. The PC is responsible for the overall management of high-end film blowing quality, which has won the favor of high-end commodity packaging

2. With the continuous development of microelectronics technology, ultra large scale integrated circuit chips (i.e. single chip computers) that integrate CPU, memory, timer/counter, parallel and serial interfaces, watchdog, preamplifier and even a/D, D/a converter and other circuits on one chip have appeared. The so-called "intelligent measurement and control system", that is, intelligent instruments, is composed of single-chip microcomputer and computer technology combined with measurement and control technology

compared with traditional instruments, intelligent instruments have the following functional characteristics:

① operation automation. The whole measurement process of the instrument, such as keyboard scanning, range selection, switch startup and closing, data acquisition, transmission and processing, display and printing, is controlled by single chip microcomputer or microcontroller to realize the automation of the measurement process

② it has self-test function, including automatic zero adjustment, automatic fault and state inspection, automatic calibration, self diagnosis and automatic range conversion. Intelligent instruments can automatically detect the fault location and even the cause of the fault. This self-test can be run when the instrument is started, and it can also be run during the operation of the instrument, which greatly facilitates the maintenance of the instrument

③ it has data processing function, which is one of the main advantages of intelligent instruments. Due to the use of single-chip microcomputer or microcontroller in intelligent instruments, many problems that were difficult to be solved by hardware logic or could not be solved at all can now be solved very flexibly by software. For example, the traditional digital multimeter can only measure resistance, AC and DC voltage, current, etc., while the intelligent digital multimeter can not only carry out the above measurements, but also has complex data processing functions such as zero shift, average, extreme value, statistical analysis and so on. It not only frees users from heavy data processing, but also effectively improves the measurement accuracy of the instrument

④ have friendly man-machine dialogue ability. The intelligent instrument uses the keyboard to replace the switch in the traditional instrument. The operator only needs to input the command through the keyboard to realize a certain measurement function. At the same time, the intelligent instrument also tells the operator the operation status, working status and the processing results of the measured data through the display screen, making the operation of the instrument more convenient and intuitive

⑤ it has programmable operation ability. General intelligent instruments are equipped with GPIB, RS232C, RS485 and other standard communication interfaces, which can easily form an automatic measurement system with multiple functions required by users together with PC and other instruments to complete more complex test tasks

3. Overview of the development of intelligent instruments

in the 1980s, microprocessors were used in instruments, and the front panel of instruments began to develop in the direction of keyboarding. Measurement systems are often connected through IEEE-488 bus. Personal instruments, which are different from the traditional independent instrument mode, have been developed

In the 1990s, the intellectualization of instruments and meters was highlighted in the following aspects: the progress of microelectronics technology was more profound, and the degradation rate slowed down to affect the design of instruments and meters; The advent of DSP chip has greatly strengthened the digital signal processing function of instruments and meters; With the development of microcomputer, instruments and meters have stronger data processing ability; The increase of image processing function is very common; VXI bus is widely used

in recent years, the development of intelligent measurement and control instruments is particularly rapid. A variety of intelligent measurement and control instruments have appeared in the domestic market, such as intelligent throttling flowmeter that can automatically compensate for differential pressure, intelligent multi-stage temperature controller that can program temperature control, intelligent regulator that can realize digital PID and various complex control laws, and intelligent chromatograph that can analyze and process various spectra

there are many kinds of intelligent measuring instruments in the world. For example, dstj-3000 series intelligent transmitter produced by Honeywell company in the United States can carry out composite measurement of differential pressure value, and can automatically compensate the temperature and static pressure of the transmitter body, with an accuracy of ± 0.1% FS; The 9303 ultra-high level meter of raca-dana company in the United States uses a microprocessor to eliminate the thermal noise generated by the current flowing through the resistance, and the measurement level can be as low as -77db; The super multifunctional calibrator 5520A produced by fluke company of the United States uses three microprocessors internally, and its short-term stability can reach 1ppm and linearity can reach 0.5ppm; The digital self-tuning regulator produced by Foxboro company in the United States adopts expert system technology, which can quickly set the regulator according to field parameters like experienced control engineers. This regulator is especially suitable for control systems with frequent or nonlinear object changes. Because this regulator can automatically set the adjustment parameters, the whole system can always maintain the best quality in the production process

4. Development trend of intelligent instruments

4.1 miniaturization

micro intelligent instruments refer to the integrated application of microelectronic technology, micromachining technology, information technology, etc. in the production of instruments, so as to make the instruments become intelligent instruments with small volume and complete functions. It can complete signal acquisition, linearization processing, digital signal processing, control signal output, amplification, interface with other instruments, interaction with people and other functions. With the continuous development of microelectronic and mechanical technology, the technology of micro intelligent instruments is maturing and the price is decreasing, so its application field will continue to expand. It not only has the function of traditional instruments, but also plays a unique role in the fields of automation technology, aerospace, military, biotechnology and medical treatment. For example, at present, several different parameters of a patient should be measured at the same time and some parameters should be controlled. Usually, several tubes should be inserted into the patient's body, which increases the chance of infection of the patient. Micro intelligent instruments can measure multiple parameters at the same time, and they are small in size and can be implanted into the human body, so these problems can be solved

4.2 multifunction

multifunction itself is a feature of intelligent instruments. For example, in order to design a digital system with fast speed and complex structure, the instrument manufacturer manufactures a function generator with the functions of pulse generator, frequency synthesizer and arbitrary waveform generator. This multifunctional integrated product not only has higher performance (such as accuracy) than the special pulse generator and frequency synthesizer, but also provides a better solution in various test functions

4.3 artificial intelligence

artificial intelligence is a new field of computer application. It uses computers to simulate human intelligence and is used in robotics, medical diagnosis, expert systems, reasoning and proof, etc. The further development of intelligent instruments will contain a certain amount of artificial intelligence, that is, a part of mental labor to replace people, so as to have a certain ability in vision (figure and color recognition), hearing (speech recognition and language comprehension), thinking (reasoning, judgment, learning and association). In this way, the intelligent instrument can complete the detection or control function without human intervention. Obviously, the application of artificial intelligence in modern instruments and meters enables us not only to solve a class of problems that are difficult to solve by traditional methods, but also to solve problems that cannot be solved by traditional methods

4.4 integrate ISP and EIT technology to realize the Internet access (Networking) of instrument and meter systems.

with the rapid development of network technology, Internet technology is gradually penetrating into the field of industrial control and intelligent instrument and meter system design, realizing the communication ability of intelligent instrument and meter system based on Internet, as well as remote upgrading, function reset and system maintenance of the designed intelligent instrument and meter system

in system programming (ISP Technology for short) is a new technology to modify, configure or reorganize software. It is the latest technology first proposed by lattice semiconductor company, which enables us to configure or reorganize the logic and functions of its devices, circuit boards or the entire electronic system at any time in every link of the product design and manufacturing process, even after the product is sold to the end user. ISP technology eliminates some limitations and connection disadvantages of traditional technology, and is conducive to on-board design, manufacturing and programming. ISP hardware is flexible and easy to modify software, which is convenient for design and development. Because ISP devices can be processed on printed circuit board (PCB) like any other devices, programming ISP devices does not need special programmers and more complex processes, as long as they are programmed remotely through PC, embedded system processor, or even Internet

emit Embedded Micro Internet technology was proposed by emware company when it founded ETI (extend the Internet) to expand the Internet Alliance. It is a technology that connects embedded devices such as single chip computers to the Internet. Using this technology, 8-bit and 16 bit single chip microcomputer systems can be connected to the Internet, and the functions of remote data collection, intelligent control, uploading/downloading data files based on the Internet can be realized

at present, ConnectOne company, VMware company, task company and domestic P & S company in the United States all provide software, firmware and hardware products of device networking based on Internet

4.5 virtual instrument is a new stage in the development of intelligent instruments. The main functions of measuring instruments are composed of three parts: data acquisition, data analysis and data display. In virtual reality system, data analysis and display are completely completed by PC software. Therefore, as long as some additional data acquisition hardware is provided, it can form a measuring instrument with PC. This kind of measuring instrument based on PC is called virtual instrument. In virtual instruments, using the same hardware system, as long as different software programming is applied, measurement instruments with completely different functions can be obtained. It can be seen that software system is the core of virtual instrument, "software is instrument"

traditional intelligent instrument

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