A computer system for measuring the thermal cot~uctivity of heat-insulating materials for construction based on an ITSM-1 meter is described. The thermal flux, temperature difference of the specimen sides, and the thermal conductivity of the material are displayed as functions of time on the computer screen.The thermal conductivity, specific heat, and thermal diffusivity of heat-insulating materials for construction must be determined experimentally. Thermal measurements are time-consuming and of comparatively low accuracy [1]. Automated instruments are required to improve the certification of construction and heat-insulating materials with respect to their thermophysical properties [2].We shall describe a computer system for determining the thermal conductivity of building materials that is based on an ITSM-I meter. Below are the results of calculations that confirm the adequacy of the physical analogs displayed on the screen.Experimental Apparatus. A block diagram of the computer system for determining thermal conductivity is provided in Fig. 1. The apparatus consists of an ITSM-1 industrial thermal-conductivity meter and a virtual measuring system [3].The 1TSM-I is adapted for testing specimens in the form of plates with an area of 625 cm 2 and a height of 1-10 cm. Heat is delivered through the upper and lower ends of the plates. Initially, the specimen is at room temperature. At some point, the temperature is raised linearly, reaching the specified value. The temperature conditions are maintained by means of heating elements and a cooler, through which running water or liquid nitrogen flows. To prevent heat losses from the heater and through the lateral surfaces of the specimen, the heat meter has a protective housing. Thermal conductivity is measured after stationary conditions have been established. The ITSM-1 contains two channels for regulation of the temperature on the surfaces of the heat exchangers and measurement of the thermal fluxes through the heat exchangers and the temperature difference on the specimen.The virtual measuring system consists of a personal computer, an interface, and a packag e of applications programs. The interface includes a 16-channel analog switch; an ADC, which converts voltages that are proportional to the thermal fluxes and temperature difference to digital code and matches the levels of the output signals to the computer; circuits that allow the control signals and temperatures to be set interactively with the ITSM-1; and an address decoder. The analog signals from the temperature sensors are sent through preamplifiers to the temperature-control and temperature-measurement systems of the ITSM-1. One of the signals passes through the analog switch to the ADC and through a 16-bit data bus to the computer for processing.The program operates interactively, acquires, processes, displays, and stores data, controls the apparatus, and checks for irregular conditions. The screen displays time dependences of the measurands -the thermal fluxes ql and qu through the lower and upper ed...
