Research On Monofilament Orientation Degree Measuring Instrument Based On Zero Crossing Detection Method

monofilament is a single slender filament obtained by heating,melting and drafting of macromolecule materials.The orientation degree of single filament will change after drafting.Orientation degree is an important index to measure the hardness and toughness of monofilament.Therefore,monitoring the orientation degree of monofilament is an important measure to ensure the quality of monofilament.At present,the commonly used methods for measuring the orientation of monofilament are X-ray diffraction,infrared spectroscopy,optical birefringence and sound velocity.The first three methods need to use large-scale instruments,and the operation is very troublesome.They are suitable for laboratory research and use.This subject needs to design a low-cost orientation measuring instrument suitable for industrial use.So it combines with the needs of the subject.,the method of measuring the orientation degree of the monofilament is the sound velocity method,that is,the orientation degree value is obtained by measuring the propagation speed of the sound signal in the monofilament.A single filament orientation measuring instrument is designed to measure the orientation of monofilament.The mechanical structure of the instrument is equipped with two ultrasonic sensors,one as the sender and the other as the receiver.When the sender is stimulated by the ultrasonic sensor,the acoustic signal will be generated.The acoustic signal propagates along the monofilament,and then propagates to the receiver.The ultrasonic sensor converts the acoustic signal into electrical signal.According to the distance between the sender and the receiver and the propagation time of the acoustic signal from the sender to the receiver,the transmission speed of the sound in the monofilament can be calculated.STM32F103VET6 is selected as the microprocessor in this subject,and the excitation pulse amplification circuit and the received signal processing circuit are designed to measure the transmission time from the sender to the receiver.The microprocessor generates a single pulse with certain width,which is processed by an excitation pulse amplifier circuit and transmitted to the ultrasonic sensor at the sender to generate acoustic signals.The received signal processing circuit filters and amplifies the electrical signals converted by the ultrasonic sensor at the receiver and sends them to the microprocessor for AD acquisition and storage.Then,the waveform collected by the microprocessor is processed by zero-crossing detection method.The method finds the time value at the zero point after the second peak,subtracting the system delay,the propagation time of the sound signal from the sender to the receiver can be obtained.The propagation velocity of sound signal in monofilament can be calculated by the formula of velocity,and then the orientation degree of monofilament can be calculated by the formula of sound velocity method.The monofilament orientation measuring instrument has the advantages of simple principle,convenience,practicality,low cost,and the measuring precision is better than 1%.It can be used to measure the orientation of monofilament,film and other macromolecule materials.