Study On The Measurement Of Wire Length Based On Pulse-Echo

With the development at high speed of domestic economic, various wires are widely used. So it is more and more important to measure the length of wire (including various cables) with higher accuracy.The technology of length measurement of cable is widely used. In the business process of electrical equipment and material, coiled electric cables need to be measured. There appear correlative instruments in the abroad, but it is difficult to be used widely inside our country because of the high cost. The system of wire length measurement is developed based on pulse-echo in the paper. Therefore, testing time will be saved, management efficiency will be improved, measurement cost will be reduced and it will have a great application foreground.Various injuries in the electric cable are caused due to the increasing length, miscellaneous lay path and long time working. Therefore, another purpose of the pulse-echo based wire length measurement system is to confirm the location of injuries on the cable.Firstly, the measurement method of the wire length based on pulse-echo is discussed in detail in the paper. Based on theory analyses of pulse propagation, pulse will be reflected on the impedance non-matching point. So the program will be carried out as follow: pulse signal is added to the measured wire, and then the reflected pulse is received at the end of the wire. The distance from breakdown point to measurement point are then calculated by round-trip time between emissive pulse and reflective pulse and wave speed of pulse in electric wire.Based on theory analyses, simulation research is carried out with the simulation platform Simulink, which is one toolbox of MATLAB. And the pulse-echo based wire length measurement method is proved to be feasibility. In the design of experimental equipment, the circuits of pulse generation and transition, which the amplitude of the pulse is alternative, are developed. According to the different length wire, pulse signal with amplitude of 5V or 12V is input to the measured wire. Reflected pulse is received at the same time. And then, the received analogue signal is transmitted to digital signal by the comparing circuit. The digital signal is then used as input of D trigger to control the insertion of high frequency pulse and count operation.Secondly, 1.2GHz high frequency pulse generator is developed. For measuring exactly from emissive pulse to reflective pulse, 1.2GHz high frequency pulse is inserted into high level range. And then is obtained with high precision by counting the number of the pulse.Thirdly, high speed counting system is designed. General counting chips can not meet the demand, because of too high frequency of the 1.2GHz pulse signal. Therefore, high speed counting system is specially developed to do the job.Last, wires with various lengths are measured using the experimental equipment, and the experimental data is analyzed which proves the correctness of the design.