This article will focus on the new controller for thermophysical research, intended for use in the educational process. The controller contains nodes of power supply, automatic control of the cells and auxiliary devices for collecting, storing and processing primary information. The controller has a built-in control panel with a functional keyboard; it can display the measurement results on a Smartphone or PC.
Thermophysical measurements belong to the category of purely indirect measurements. To register temperature elds and heat uxes, thermocouples and thermistors are used everywhere, which convert the temperature into electrical signals. Therefore, in the composition of any thermophysical measuring device, along with a heat cell, an electrical measuring complex is equally present. A very strict requirement is imposed on its technical characteristics due to low-current electrical signals of thermoelectric sensors.
A controller designed for servicing heat-measuring cells should be a complex multifunctional electronic device operating according to a given program, which includes several dozen interconnected procedures, controlling all stages of a thermophysical experiment.
For many years, the employees of the Department of Thermophysics of the
St. Petersburg State Academic Technical University (now the school of
biotechnology and cryogenic systems of the ITMO University) and the department of
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Commons License Attribution 4.0 International (CC BY 4.0).
computer engineering ITMO (now the faculty of software engineering and
computer systems of the ITMO University) participated in the joint development of
a number of thermophysical devices of the ITS series and TFK controllers. The
results of this collaboration are detailed in publications. [
Together, a number of devices for thermal measurements of various materials were created (Table 1.)
This article will focus on the new controller for thermophysical research, intended for use in the educational process. The controller contains nodes of power supply, automatic control of the cells and auxiliary devices for collecting, storing and processing primary information. The controller has a built-in control panel with a functional keyboard; it can display the measurement results on a Smartphone or PC. The controller provides simultaneous operation of up to 8 primary measuring sensors with a threshold sensitivity of about 10 V with sampling resolution of sensors from 0.02 s or more. There is the possibility of working with a personal computer. Control and information signals are transferred between the PC and the controller via the USB port.
The laboratory complex allows you to study thermal processes in the temperature range from minus 196 C to 100 C: thermal conductivity and thermal resistance; heat capacity, enthalpy, heat and power of internal sources; initial moisture content and cryoscopic temperature; to conduct studies of the kinetics of phase and structural transformations in moisture-containing materials.
Measurement of thermal conductivity and thermal resistance of various heat-insulating, building and structural materials near room temperature.
Research of thermal and humidity characteristics of nely dispersed moisture-containing materials in the temperature range ({30 ... 20) . The thermal properties of any substances and materials, both liquid and solid, can also be studied.
Measurement of thermal conductivity and heat capacity of substances at atmospheric pressure in the temperature range ({30 ... 80) .
The study of thermal and humidity characteristics of materials in the temperature range ({30 ... 20) . It is possible to study the thermal properties of ordinary substances and materials.
Measurement of heat capacity at atmospheric pressure in the temperature range ({30 ... 80) C.
Measurement of internal heat sources arising from chemical reactions, in the processes of dissolution, oxidation, etc.
Measurement of thermal conductivity, thermal resistance and heat capacity of solid electrical insulating materials.
Measurement of thermal conductivity, thermal resistance and heat capacity of solid non-metallic materials
At the moment, we can con dently say that instrument controllers designed
for close integration with devices for measuring physical quantities are
cyberphysical systems (CPS)[
As a controller for automating thermophysical measurements, we propose
using the SDK-1.1M training laboratory bench [
DS18b20 temperature sensors are connected directly to the SDK-1.1M microcontroller, thermocouples and resistance thermometers are connected to the ADC chip with an integrated SPI interface. All the main communication interfaces SDK-1.1M (SPI, I2C, UART), including the software-based OneWire protocol, are connected to the built-in logic analyzer for more convenient debugging. The architecture of the module is shown in Picture 3.
A key component of the expansion module is the AD7194 chip, a low noise, highly integrated system for precision measurement systems. At the heart of the device is a 24-bit - ADC, built-in PGA, which allows low-amplitude signals to be fed to the microcircuit inputs. The microcircuit inputs can be con gured as eight di erential or sixteen pseudo di erential. Functional diagram of the AD7194 is shown in Picture 4.
The rst software prototype was developed, with the development of which di culties began. The implementation of native software for Windows (Windows Forms and WPF) and Android (Java / Kotlin) was abandoned for several reasons: { The costs of programming native desktop applications are quite high in the face of changing system requirements; { We need cross-platform. students often come to classes with their laptops, many Linux and Mac OS X. Users have mobile phones on Android and iOS. Implementing and supporting native applications for all platforms is complex and expensive; { In connection with the beginning of the development of a system of heterogeneous modeling of CFS, it turned out to be very useful to implement training software in the form of web services; { Native desktop programs are gradually becoming obsolete and superseded by Web technologies.
An analysis of technologic stacks was carried out, in which the main criteria were capabilities, entry threshold, development speed, prevalence, support and prospects. As a result, the software for TFK-4.0 consists of a program for SDK1.1M, a program for a student and teacher. The following technologies were used.
{ FreeRTOS; { LwIP; { USB HID; { AD7194 driver; { DS18b20 driver.
{ Node.js; { Rest API..
Javascript was chosen as the main language of the top level, Node.js. was chosen as the platform for building the backend. The frontend is implemented using the Vue.js. framework. To implement the embedded software, the C language is used for the STM32 + HAL + FreeRTOS platform. Currently, this hardware and software is in the implementation phase.
Any condensed (solid and liquid) substances and materials of inorganic and organic nature (heat insulators, polymers, food products, semiconductors, metals, etc.) can be used as the objects under study.
An automated training laboratory stand is designed to equip research and educational laboratories of higher educational institutions with a heat engineering pro le. According to its operational and metrological properties, this automated complex may also be of interest in various elds of scienti c research and industries for certi cation of thermal characteristics of products.