Ultrasonic thickness gauge measurement error prevention methods
1. Ultra-thin materials With any ultrasonic thickness gauge, when the thickness of the material to be measured falls below the lower limit of the probe's use, this will result in a measurement error, and, if necessary, the minimum limiting thickness can be measured by comparison with a test block. When measuring ultra-thin materials, an error result called "double refraction" sometimes occurs, which results in the display reading is twice the actual thickness, and another error result is called "pulse envelope, cycle jumping", which results in the measured value is greater than the actual thickness, to prevent this type of error, to prevent this type of error, it is necessary to use the test piece comparison method. Another type of error result is called "pulse envelope, cycle jump", which results in a value greater than the actual thickness. To prevent this type of error, the measurement should be repeated when the material at the lower limit of the critical probe is used. 2.
2. Rust spots, corrosion pits, etc. Rust spots, pits, etc. on another surface of the material to be measured will cause irregular variations in the readings, and in extreme cases, even no readings, and very small rust spots are sometimes difficult to detect. When pits are found or suspicion is felt, this area of the measurement must be very careful, the probe can be selected crosstalk insulation plate positioning at different angles to make multiple tests. 3.
3. probe wear probe surface for the acrylic resin, long-term use will increase the roughness, resulting in decreased sensitivity, the user can be sure that the cause of this error, the user can use sandpaper or oil stone a small amount of sanding probe surface to make it smooth and ensure parallelism. If it is still unstable, it is necessary to replace the probe.
4. Use of the "ZERO" key This key should only be used when coupling the probe to a standard test block on the instrument panel for calibration.
This key should only be used to calibrate the probe by coupling it to a standard test block on the instrument panel, and should not be used on any other test block, as this will cause measurement errors.
5. Laminates, composites Measurement of uncoupled laminates is not possible because ultrasound cannot penetrate into uncoupled spaces. Since ultrasonic waves do not propagate at a uniform speed through composite materials, any instrument that measures thickness using the ultrasonic reflection principle is not suitable for measuring laminates and composites.
6. Anomalous thickness readings The operator should have the ability to recognise anomalous readings, which are usually caused by rust spots, corrosion pits, and internal defects in the material being measured. Solutions can be found in sections 6 and 7. If necessary, an ultrasonic flaw detector can be used for closer inspection.
7. Couplant use and selection The couplant is used as a high-frequency ultrasonic energy transfer between the probe and the material under test. If the choice of type or use method is not appropriate will likely cause errors or coupling mark flicker, can not measure the value. The coupling agent should be used in the right amount and applied evenly. Selection of the appropriate type of coupling agent is important, when used on smooth material surfaces, low-viscosity coupling agent (such as randomly configured coupling agent, cleaner oil, etc.) is very suitable. When used on rough material surfaces, or vertical surfaces and top surfaces, higher viscosity couplers (e.g., glycerin paste, butter, grease, etc.) can be used. Coupling agents of various formulations are available everywhere.
