Abstract: Liquid density is an important parameter in industrial production, especially in the pharmaceutical and chemical industries. This paper employs a dual-probe structure and utilizes the sound velocity method to measure liquid density, with the key being the accurate measurement of the ultrasonic wave propagation time in the liquid. Traditional circuit designs often suffer from unsatisfactory measurement results due to the influence of chip clock frequency. To obtain accurate measurement time, a high-precision counter is designed using an FPGA with a high internal clock frequency. Furthermore, to reduce external circuitry and avoid electromagnetic interference between electronic components, the control and calculation modules in the system are also implemented using an FPGA. Experimental results demonstrate that this method offers superior reliability and speed.
Keywords: ultrasonic liquid density, FPGA, sound velocity method
Ultrasonic Liquid Density Sensor Based on FPGAAbstract: Liquid density is one of the important parameters in many industrial fields, especially in pharmacy and biochemistry industry. In the design, the double-probe structure is adopted, and the operation principle of the ultrasonic density sensor is based on time law. So, the time measurement precision must be very high. In traditional circuit design, for the limited by the internal clock of the chip, the perfect result can't be got. By using the FPGA to design the high precision counter, the accurate measurement time can be achieved. To reducing the peripheral circuit's size and the electromagnetic interference between the electronic devices, the FPGA also be used to design the control and operation module. Through the experiment, the result indicated that this method has the advantages in speed and reliability.
Keyword: ultrasonic liquid density FPGA sound velocity method
0 Introduction
Liquid density is a crucial parameter in many industries, directly impacting production process control and decision-making. Therefore, rapid and accurate online detection of liquid density is of paramount importance. This is especially true in industries such as petroleum, chemical, food, and pharmaceuticals, where density measurement directly affects the national economy and consumer safety.
1. Working principle of ultrasonic liquid density meter
There are various methods for measuring the density of liquids using ultrasound. With the rapid development of electronic technology, the method of measuring density by means of the speed of sound has been widely applied. This is because when ultrasound propagates in a liquid, the speed of sound and the density of the liquid follow the following relationship:
(1-1)
In the formula, C is the speed of ultrasonic wave propagation in the liquid; ρ is the density of the liquid; and K is the compressibility coefficient. For a specific liquid, the compressibility coefficient K is a constant. The density of the liquid can be calculated by measuring the speed of ultrasonic wave propagation in the liquid. The speed measurement is determined by the path length and propagation time of the ultrasonic wave in the liquid.
2. Design of FPGA-based control and computing circuits
Because FPGA chips operate at very high frequencies, they are easily designed and implemented with clock circuits reaching tens or even hundreds of megahertz, making them ideal for designing high-speed timing circuits. This design utilizes Altera's Cyclone II series chips, which can operate at frequencies up to 400MHz, sufficient for the needs of this design. The software development platform is Quartus II.
For details, please click: FPGA-based Ultrasonic Liquid Density Sensor
