Research On Wood Moisture Measurement System Based On Interdigitated Single Planar Capacitance Sensor

At present, the domestic wood moisture content detection technology is relatively weak,most of the enterprises in the detection of wood moisture content is limited to the resistance method, this method is low accuracy and poor anti-interference. Wood products in the domestic market often appear quality problems because the moisture content testing is not accuracy. According to the current development situation at home and abroad, it is clear that electromagnetic wave nondestructive testing is the development direction of future wood moisture content measurement. Electromagnetic wave nondestructive detection of capacitance sensor method compared with other methods, with no space restrictions, high accuracy, on the environment requirements low, and interdigital capacitive sensor accuracy, signal strength,sensitivity is more outstanding. Therefore, based on the interdigital capacitive sensing device of wood moisture rate detection system research to improve the domestic wood products enterprise competitiveness has great significance.This paper mainly contains the following aspects of the work:Firstly, according to the theory of electromagnetic field and the dielectric properties of wood, the overall design of the detection system of wood moisture content in this paper,including the overall structure of the system and the detection principle of the system, is determined in the first place. The wood moisture content measurement system includes: the cross finger type capacitance sensor, data acquisition system and computer data processing system.Secondly, based on the finite element method, the influence of the structure of the capacitance sensor on the detection performance is analyzed, and the structure design of the cross finger capacitive sensor is completed. On the basis of this, the mathematical model of the cross finger type plane capacitance sensor is established based on the Maxwell electromagnetic field theory. By using the established mathematical model, the polynomial between the capacitance value and the wood dielectric constant is calculated and calculated.MAXWELL ANSOFT based on electromagnetic field simulation software for virtual modeling, and the results of the simulation calculation and the use of theoretical model calculation results are compared to verify the correctness of the mathematical model established in this paper.Then, the data acquisition system of wood moisture content monitoring system was designed, including hardware design and software design. Hardware design including data acquisition card selection and configuration, the design of the hardware detection circuit.Software design includes the VC++ development platform based on the MFC man-machine interface and the establishment of SQL database and communication. The hardware detection circuit comprises a power supply circuit,an excitation signal generation circuit,a C/V conversion circuit, an amplifying circuit and a filter circuit.At last, the experiment of wood moisture content detection was carried out by using larch as wood sample. Using MATLAB to detect the moisture content of the system and the absolute dry measured water content values were compared and analyzed. The reliability and practicability of the wood moisture content detection system are verified. Development of wood moisture content measurement system based on cross finger planar capacitance sensor.