The principle of intelligent instruments and their functional characteristics

It is understood that with the development of smart instruments, the application of traditional instruments has been greatly expanded. The characteristics of smart instruments are strong features, low consumption, etc. What are their main operating principles and functional features?

1. The working principle of intelligent instrument The sensor picks up the information of the measured parameter and converts it into an electric signal. After filtering to remove the interference, it sends it into multiple analog switches. The single-chip microcomputer commutates the analog switch one by one and sends the signals of each input channel to the program control one by one. Gain amplifier, the amplified signal is converted into the corresponding pulse signal by a/d converter and then sent to the single-chip microcomputer; the single-chip microcomputer performs corresponding data operation and processing (such as nonlinear correction, etc.) according to the initial value set by the instrument; The result is converted into the corresponding data for display and printing; at the same time, the MCU compares the calculation results with the set parameters stored in the on-chip flash ROM (flash memory) or e2prom (electrically erasable memory). After that, according to the calculation results and control requirements, output corresponding control signals (such as alarm device triggers, relay contacts, etc.). In addition, the intelligent instrument can also be composed of a distributed measurement and control system with a PC. The single-chip microcomputer can be used as a slave to collect various measurement signals and data. The serial communication can be used to transmit the information to the host PC and be managed globally by the PC.

2. Features of smart instruments With the continuous development of microelectronics technology, integrated cpu, memory, timer/counter, parallel and serial interfaces, watchdogs, preamps, and even a/d, d/a converters The VLSI chip (ie, SCM) appears on a chip as a circuit. Take the one-chip computer as the main body, combine computer technology and measurement and control technology together, and form the so-called intelligent measurement control system, namely intelligence instrument.

Compared with traditional instruments, smart instruments have the following features:

1 Operational automation. The entire measurement process of the instrument, such as keyboard scanning, range selection, switch start closure, data acquisition, transmission and processing, and display printing, is controlled by a single-chip microcomputer or a microcontroller to achieve full automation of the measurement process.

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

3 has data processing capabilities, which is one of the main advantages of smart instruments. The use of a microcontroller or microcontroller in smart instruments has made many problems that were previously difficult or impossible to solve with hardware logic, and can now be solved with great flexibility using software. For example, a conventional digital multimeter can only measure resistance, AC/DC voltage, and current, while an intelligent digital multimeter can not only perform the above measurements, but also perform measurements such as zero shift, averaging, extreme value, and statistics. Analysis and other complex data processing functions not only free the user from heavy data processing, but also effectively improve the measurement accuracy of the instrument.

4 has a friendly human-machine dialogue ability. The intelligent instrument uses the keyboard instead of the switch in the conventional instrument, and the operator can realize some measurement function simply by inputting a command through the keyboard. At the same time, the intelligent instrument also informs the operator through the display screen of the instrument's operating conditions, working conditions, and the results of measurement data processing, making the operation of the instrument more convenient and intuitive.

5 has programmable control capabilities. General smart instruments are equipped with standard communication interfaces such as gpib, rs232c, rs485, etc. It is very convenient to form an automatic measurement system with various functions required by the user together with the pc and other instruments to complete more complicated test tasks.