Ultrasonic thickness gauge thickness calibration and sound velocity adjustment
Due to the influence of factors such as ambient temperature and operating voltage, some parameters of the measurement system often drift, so the thickness calibration of the instrument should be performed during measurement. The calibration operation is to use an instrument to measure a 5mm thick standard test block. If the instrument shows that it is not equal to 5mm, the thickness should be calibrated. The old-fashioned thickness gauge is achieved by adjusting the potentiometer knob. This design is completed by the thickness calibration key. When calibration is required, press the thickness calibration key, and the microcontroller will execute the thickness calibration program, compare the measurement results with the standard thickness, and perform addition and subtraction processing based on the results to complete the calibration.
Sound speed setting
When the ultrasonic thickness gauge measures the thickness of different materials, since the speed of ultrasonic waves propagating in different materials is different, the sound speed of the material needs to be set. For example, the sound speed of steel is 5950m/s, and the sound speed of zinc is 4170m/s. In old-fashioned instruments, this operation is completed by a mechanical 3-digit BCD code disk switch and a preset counter to control the number of times the gate is opened. For materials with high sound speed, the gate is opened more times, and for materials with low sound speed, the gate is opened less often. . In this design, the sound speeds of nine typical materials: cast steel, steel, aluminum, copper, brass, zinc, quartz glass, polyethylene, and polyvinyl chloride are put into the storage unit in table form. When used, the sound speed is set by the sound speed setting key. Select, and then the P1.7 port of the microcontroller collects the transmitted pulses and subtracts them to count them to control the number of times the gate is opened, making the sound speed setting operation very simple.
Sound speed adjustment
The sound speed settings of the 9 typical materials mentioned above are selected by the sound speed setting key. When measuring the thickness of atypical materials, the sound speed setting is completed by the sound speed increase and sound speed decrease function keys. Press the sound speed increase or sound speed decrease key, and the sound speed value displayed on the LCD screen will increase or decrease until the sound speed is adjusted to the required sound speed. At this time, the sound speed adjustment program will store the adjusted value in the sound speed storage unit for later use.
