The Design Of Ultrasonic Viscosity Measurement System Based On DSP&CPLD Technology

The viscosity measurement has been utilized widely on the research of textil industry,petroleum,chemistry,food processing and medical application,.etc,and come to be the important standard to contorl the quantity of the product and the technological procedure.The viscosity measurement consists of the dynamic measuremen and the static measurement.As one of the important static viscosity analyzers,photoelectric falling-sphere viscometer shows several shortcomings in the process of measuring,the spectrum limit to photoelectric sensors,ray interference from sun,low accuracy to measure falling-sphere speed and unignorant error.These have a great negative influence to viscosity-measure accuracy and efficiency.With the progress of automation of testing instrument and the research of viscosity measurement,viscosity measurement has changed from photoelectric falling-sphere viscometer to energy-attenuation viscometer.Nowadays some foreign companies research and produce new varieties of portable viscometers on the basis of the principle of energy attenuation of the back wave.However,photo-electric falling-sphere viscometer is still applied to measure static viscosity in China, thereforeit is imperative to improve the development of viscosity measurement and research the complete-function static-viscosity measurement system.This paper has elaborated a set of new ultrasonic measurement system of static viscosity based on DSP+CPLD.The overall organizations of the viscosity-measure part and the measurement method have made the significant innovation,the way of Ultrasonic Doppler frequency shift is utilized in stead of the way of photoelectric falling-sphere,and the electric circuit design of frequency-shift measurement part and the method of measurement is improved further.In the design of frequency-shift measurement module,MAX7128S CPLD is used to reduce delay time and enhance the surveying accuracy and high operation efficiency on the basis of the improved principle of the phase coincidence.At same time,simplifying electric circuit, shortening software development period and modifying design conveniently are also the merits of it.As the core chip of the processing control unit of system, TMS320VC5402 not only is in charge of Logic control,but efficiently processes high-speed data from the front channel to meet the requirement of real-time performance. Compared with the photoelectric falling-sphere viscometer,this system has the quicker speed and the higher precision.Installing and debugging are more convenient. The using of CPLD simplifies the design of the hardware and make things convenient for secondary development.These advantages make it have more practical value on viscosity measurement in China.