Design of intelligent pressure sensor based on 51 single chip microcomputer

　　0 Introduction

　　All the single-chip microcomputers currently compatible with Intel 8031 ​​instruction system are collectively referred to as 51 single-chip microcomputers. Intel's 8031 ​​single-chip microcomputer is the ancestor of 51 single-chip microcomputers. 8031 ​​single-chip microcomputer is one of the most widely used 8-bit single-chip microcomputers. With the development of Flash rom technology, it has also been continuously developed and widely used in industrial measurement and control systems. ATMEL's AT89 series is the most representative model of 8031 ​​single-chip microcomputers. 51 single-chip microcomputer is a basic entry-level single-chip microcomputer and is also the most widely used one. At present and for a long time in the future, compatible models of the 51 series will occupy a large market.

　　The traditional design ideas and methods of control systems have been fundamentally changed by the application of 51 single-chip microcomputers. Single-chip microcomputers are now being used to implement most of the control functions that are implemented by hardware circuits through software. Intelligent digital calculation control, fuzzy control and adaptive control can be implemented through single-chip microcomputers, thereby changing the PID adjustment in automatic control. With the widespread application of single-chip microcomputers, micro-control technology that replaces hardware with software and can improve system performance will continue to develop and improve.

　　Pressure sensor, the English name is pressure transducer, it refers to a sensor that can sense pressure and convert it into a usable output signal. Pressure sensors are very commonly used in industrial practice, and are widely used in various industrial automatic control environments. They are also involved in many industries, such as water conservancy and hydropower, intelligent buildings, production automatic control, aerospace, petrochemical, electric power, shipbuilding, pipelines and other industries.

　　1. Characteristics of intelligent pressure sensor

　　(1) The measurement range and functions have been expanded, and measurements that meet parameters and various requirements can be achieved.

　　(2) Sensitivity and measurement accuracy have been improved. Weak signal measurements, various corrections and compensations can be performed, and measurement data can be stored and accessed.

　　(3) The stability and possibility of measurement are improved, and it is not affected by external interference. The measurement is carried out selectively, and the intelligent pressure sensor has high performance.

　　(4) It can self-diagnose, accurately locate the fault location, and quickly identify the fault status. It can also realize functions that cannot be realized by hardware.

　　(5) There are many output forms and digital communication interfaces, which are diverse.

　　Smart pressure sensors or intelligent pressure sensors are sensors that have both detection and information processing functions.

　　2. Data collection and processing functions of intelligent pressure sensors

　　Preprocessing the output signal of the pressure sensor is a must before the pressure sensor can be intelligentized. Due to the wide variety of detected signals, the output signals also have analog, digital and switch quantities, etc. The input quantity of the MD conversion is not only composed of the output signal of the pressure sensor, but also the circuit must be preprocessed to convert the sensor output signal into a unified voltage signal or periodic signal.

　　(1) Data collection. The pressure sensor signal is processed and becomes the point analog signal required by the A/D converter. The analog digitization of the analog-to-digital converter (MD) converts the input signal into a digital signal. These changes are obtained through sampling, quantization and encoding.

　　(2) Data processing. The A/D converter converts the data output signal of the pressure sensor and processes the obtained digital signal according to the needs, such as scale conversion, nonlinear compensation, temperature compensation and digital filtering. Otherwise, it cannot be directly input into the microprocessor for application program use.

　　The following aspects are all the contents of data processing: ① Collect data, summarize the required information; ② Convert data, convert the required information into a form suitable for use by microprocessors; ③ Group data, effectively group data, and this grouping is done according to related information; ④ Organize data, in order to facilitate processing and correct errors, the data must be sorted or arranged in other ways; ⑤ Calculate data, in order to obtain further information, various arithmetic and logical operations must be performed on the data; ⑥ Store data, save the original data and calculation results for later use; ⑦ Search data. The results are output according to user requirements by providing information in a useful format.

　　3 Design of intelligent pressure sensor based on 51 single chip microcomputer

　　The overall structure design, sensitive element design, sensor process design and software design are the main processes of intelligent pressure sensor design, which are designed according to the technical indicators proposed for intelligent pressure sensors. The author of this article introduces the overall structure design and software design of intelligent pressure sensors.

　　(1) Overall structural design: Semiconductor sensitive elements, amplifiers, conversion switches, dual-integral A/D converters, single-chip microcomputers, interface circuits, IEEE-488 standard interfaces, memory, and some peripheral circuits are combined to form an intelligent pressure sensor.

　　(2) Software design. The control program, data processing program and auxiliary program are the three aspects of the intelligent pressure sensor software based on the 51 single-chip microcomputer. [page]

　　Figure 1 Circuit diagram of silicon pressure sensor

　　Multifunctionality is an important feature of smart pressure sensors, which can be implemented in two ways:

　　① The command of the selected function is issued by the user through the keyboard; ② Automatic type, the compiled data acquisition and processing program is coordinated by the internal function control program, or the reception of external signals is carried out through the IEEE--488 bus, and the control command is issued by the intelligent pressure sensor, and then through self-calibration, tracking, over-limit alarm, output printing, keyboard, display, A/D conversion and other circuits and interfaces 1=I, so as to ensure that the intelligent pressure sensor works in an orderly manner.

　　According to the source program flow chart of FIG2, the following can be designed: install the intelligent pressure sensor, calibrate, convert the signal into digital code, store it in E.PROM, and then output the desired value, as shown in FIG3.

　　Figure 3 Smart sensor source program flow chart

　　By utilizing the sealing technology of integrated circuits and sensors, the silicon force-sensitive element with a temperature-sensitive diode can be mixed, integrated and connected with a single-chip microcomputer, A/D converter, interface circuit, etc. by the intelligent pressure sensor part, which can automatically correct and compensate the test output signal. The functions of program control, calculation and processing exist in the whole system, and can be stable for a long time in situations where the ambient temperature changes.

　　Figure 4 Intelligent pressure sensor correction and display flow chart

　　4 Conclusion

　　Intelligent pressure sensor is widely used in electronic scales or business measurement and other fields. It can accurately measure various values ​​and is an intelligent instrument for detecting pressure. In order to enable the system to directly display the pressure, the intelligent improvement can be controlled by the keyboard, which is the purpose of this article.