Hardware and software components of smart meters

1. Composition of smart instrument hardware

The hardware part of the smart instrument includes the controller and its interface circuit, analog input channel, switching input channel, analog output channel, switching output channel, interface circuit, human-machine channel (such as keyboard, display interface circuit, etc.) and other peripherals Device (printer, etc.) interface circuit. The composition of the intelligent instrument system is shown in Figure 1.

Figure 1 Block diagram of intelligent instrument system

1. Controller and its interface circuit

The controller and its interface circuit include the controller, program memory, data memory, input and output interface circuit and expansion circuit, which can perform necessary numerical calculations, logical judgments, data processing, etc.

2. Input and output channels

The input and output channels are the connection channels for signal transmission and transformation set up between the intelligent instrument controller and the measured monitoring system. It includes analog input channels, switching (digital) input channels, analog output channels, switching (digital) output channels, etc. The function of the input and output channels is to convert the signals of the measured monitoring system into codes that the controller can receive and recognize; convert the control commands and data output by the controller and use them as control signals for actuators or switches to control the measured monitoring system. Perform the desired action.

In the computer monitoring system, some basic switching input and output signals need to be processed, such as the closing and opening of the switch, the connection and disconnection of the switch, the lighting and extinguishing of the indicator light, the opening and closing of the valve, etc. These signals are all It appears as binary "0" and "1". The changes in the corresponding binary bits in the computer system characterize the characteristics of the corresponding device. The switching input and output channel is to realize the connection between the external switching signal and the computer system, including the input signal processing circuit and the output power amplifier circuit.

The analog input and output channels are composed of data processing circuits, A/D converters, d/a converters, etc., and are used to input and output analog signals. Among them, the task of the analog input channel is to convert analog signals monitored by pressure transmitters, temperature sensors, liquid level transmitters, flow meters, etc. into binary digital signals and send them to the computer for processing. The task of the analog output channel is to convert the digital signal output by the computer into an analog voltage or current signal. Drive the corresponding actuator action to achieve the control purpose.

3. Communication interface

The communication interface is used to exchange data between smart instruments and other external computers or intelligent peripherals.

4. Human-machine channel

The human-machine channel is the input and output channel for establishing contact and exchanging information between people and intelligent instruments, including human-machine interface and human-computer interaction equipment. The human-machine interface is a control circuit that realizes information transmission between the microcontroller of the smart instrument and the human-computer interaction device. Human-computer interaction device is one of the most basic devices in the smart instrument system. It is an external device that establishes contact and exchanges information between people and smart instruments. Common human-computer interaction devices can be divided into two categories: input devices and output devices. Among them, the input device is when people input information to the smart instrument system, such as input keyboards, switch buttons, etc.; the output device is when the smart instrument system directly provides system operation results to people, such as display devices, printers, etc. Through the human-machine channel of the smart meter, you can input commands and data to the smart meter, understand the running status of the smart meter and display relevant working parameters.

The working process of the smart instrument is as follows: the input signal must be transformed, amplified, shaped, compensated, etc. through the switching input channel circuit or the analog input channel circuit. For analog signals, they need to be converted into digital signals through an A/D converter, and then sent to the microcontroller through the interface. The microcontroller performs a series of tasks such as processing, calculation and analysis on the input data, and sends it to the display or printer through the interface. It can also output switching signals or convert them into analog signals through the d/a converter of the analog channel. Data communication can be achieved through serial interfaces (such as rs-232, etc.) to complete more complex measurement and control tasks.

2. Software composition of smart meters

The hardware only provides the underlying material basis for the smart instrument system. To make the smart instrument work properly, the corresponding software must be provided or developed. As shown in Figure 2, smart instrument software can be divided into system software, support software and application software.

Figure 2 Software structure of smart meters

System software includes real-time operating systems, boot programs, etc.; supporting software includes compilers, high-level languages, etc.

Application software is a system designer's control and management program for a certain measurement and control system. The application software of smart meters includes monitoring programs, interrupt service programs and functional modules that implement various algorithms. The monitoring program is the central link of the instrument software. It receives and analyzes various commands, and manages and coordinates the execution of the entire program; the interrupt service program makes an interrupt request at the human-machine interface or other peripheral devices, and directly responds to the microcontroller. Transfer to execution in order to complete real-time processing tasks in time; the function module is used to realize the data processing and control functions of the instrument, including various measurement algorithms (such as digital filtering, scaling transformation, nonlinear correction, etc.) and control calculations (such as pid control, feedforward control, fuzzy control, etc.).

Only when software and hardware cooperate with each other can the advantages of the system be brought into play and a smart instrument system with higher performance can be developed.