Measuring the Material Moisture in Construction Industry with Trime-TDR Technology

摘要

The paper introduces the TDR technology, compares and analyses the TDR method and capacitive and microwave methods using the relationship of dielectric constant with frequency. It is shown that TDR method has the great advantage in the measuring principle. Trime-TDR technology is described, which is different from the conventional voltage-sampling technology. Trime-TDR solves the key problem of TDR to measure the extreme short transit time of the electromagnetic wave. An iterative algorithm was developed to determine the transit time with a resolution of 3 ps, which enables the probe relative small dimension and the measurement in wide range. Based on Trime-TDR a new probe is set up for the materials in construction industry, which can determine the moisture, temperature and conductivity simultaneously. The probe structure, types, the measuring and calibration process and the measuring modes are explained. These probes can be used on line and in the laboratories. The various probe types and measuring modes are suitable for different applications. 15 groups of the curves of material calibraton and temperature shift compensation can be saved in a probe and be selected on line. An own material calibration may be made and saved by self. An application example of Pico-Mix in a sand and concrete mixer is given. Pico-Mix was set to the measuring mode of floating average with a filter and achieved the accuracy ±0.1%. The Trime-TDR probe has been proved to be reliable, quick, easy, economic and of high accuracy.