Research On Electronic Unit Of Intelligent Metal Tube Rotameter

Flow is a primary parameter to be measured and controlled in industrial production, scientific experiments, energy metering and other fields in the daily life. Rotameter is a kind of classical variable area flow meter. It is widely used due to its simplicity, high reliability, low pressure loss and high stability.This thesis is about the electronic part of the metal tube rotameter, which is based on the magnetic sensors and microcontroller MSP430.Both magnetic resistance HB-QCZ111 and dual magnetoresistive sensors HMC1512 were tested in measure the angle of magnet. The dual magnetoresistive sensors HMC1512 design was proved to be better by many experiments, including position experiments, temperature experiments and flow experiments, and to be applied in the electronic part of the metal tube rotameter.In practice, the flow rate change causes the change of the float s position in the metal tube and leaded to rotation of the coupling magnet. The change of magnetic angle is detected by the magnetoresistive sensors and generates a signal. The electric circuit processed the signal and made it available for the microcontroller for sampling. At the same time, the temperature measurement circuit compensated the environment. The hardware system was powered by 24V DC. It consists of RS485 communication transceiver port, extra watchdog circuit, power protection circuit, and outputs two-wire current in 4~20 mA.The software of microcontroller MSP430 was modular designed,including modules such as the initialization, A/D sampling, PWM wave output, UART communication , and so on. Furthermore, these modules were optimized in the main program.This system could sample the temperature, calculate the instantaneous flow, and display them on the LCD screen. Users could use computers to connect the RS485 communication transceiver port to set parameters. According to this design, three prototypes in different sizes were built and calibrated. Experimental results demonstrated 1.5% measuring precision ratio of the metal tube rotameter with the dual magnetoresistive sensors HMC1512 and microcontroller MSP430 design.