In various fields such as industrial production and equipment maintenance, the measurement of material thickness is a key link to ensure product quality and operation. The AG-200A handheld high-precision ultrasonic thickness gauge, with mature technical principles and practical functional design, is widely used in industries such as petroleum, chemical, metallurgy, and shipbuilding, providing reliable solutions for measurement needs of different materials and thicknesses. Its core working principle is based on the propagation characteristics of ultrasound, and through scientific signal processing and data calculation, it realizes the perception of material thickness.
Core principle: Ultrasonic pulse reflection mechanism
The working core of AG-200A handheld high-precision ultrasonic thickness gauge follows the principle of ultrasonic pulse reflection, which is similar to the logic of light wave propagation measurement, that is, by detecting the propagation time and velocity of the wave to derive the relevant parameters of the measured object.
The probe end of the instrument emits ultrasonic pulses of a specific frequency, which propagate at a constant speed inside the material being measured. When the ultrasonic pulse reaches the lower surface of the material (or the interface between different media), reflection occurs, forming a reflected echo and returning to the receiving end of the probe along the original propagation path. The signal processing system inside the instrument captures the complete time difference between the transmission and reception of ultrasonic waves, and then combines it with the known propagation speed of ultrasonic waves in the material to calculate the thickness using the core formula "thickness=(ultrasonic propagation speed x propagation time difference)/2". The derivation of this formula is based on the characteristics of back and forth propagation of ultrasonic waves, and the propagation time difference corresponds to the total duration of ultrasonic waves from the probe to the material interface and back to the probe. Therefore, it needs to be divided by 2 to obtain the actual thickness of the material.
It is worth noting that the application of this principle requires the following prerequisites: the tested material must be a good conductor of ultrasonic waves, capable of propagating ultrasonic waves at a stable speed inside it, and the back of the material must provide a reflective interface to ensure that the reflected echoes can be accurately received by the probe. AG-200A can adapt to various materials that meet the above conditions, such as metal, plastic, ceramic, glass, fiber, etc., and has a wide range of applications.
Key technical support: Ensuring the core mechanism of measurement
Multi mode measurement adapted to different scenarios
To meet complex measurement requirements, AG-200A has set up multiple measurement modes, each optimized based on the principle of pulse reflection:
MB-E mode (transmitting pulse starting wave to one echo): suitable for thickness measurement of conventional materials, directly capturing the time difference between the starting wave and one reflected echo, easy to operate;
I-E mode (interface wave to primary echo): For materials with slight dielectric layers on the surface, surface interference is reduced by identifying the signals of interface waves and reflected echoes;
E-E mode (through coating measurement): It can penetrate non-conductive media such as paint layers and coatings on the surface of materials, directly measure the thickness of substrates without the need for surface coatings, and avoid damage to the measured object;
ME-E mode (multiple echo measurement): By capturing signals from multiple reflected echoes, the measurement stability of materials with strong sound attenuation is improved;
THIN mode (thin-walled measurement): For materials with thinner thickness (up to 0.14mm, steel material), optimize the signal detection algorithm to distinguish between the initial wave and the reflected echo, and avoid measurement errors caused by signal overlap.
Sound velocity calibration and adaptation mechanism
The propagation speed of ultrasound varies in different materials (such as aluminum with a sound speed of 6340-6400m/s, steel with a sound speed of 5920m/s, and plastic materials with a sound speed mostly in the range of 2000-3000m/s), and the accuracy of sound speed directly affects the thickness calculation results. AG-200A provides a comprehensive calibration mechanism that supports single point calibration, multi-point calibration, and manual calibration modes. It can calibrate both sound velocity and probe zero position simultaneously, and also supports V-path calibration.
Users can calibrate using standard calibration blocks (standard 4mm steel block), and the instrument will automatically adjust the sound velocity parameters based on the difference between the standard thickness of the block and the measured time, ensuring accuracy in measuring different materials. In addition, the instrument has built-in sound velocity data for various common materials, which users can directly call or manually input the sound velocity values of the materials, further expanding the application scenarios.
Signal processing and gain adjustment
To ensure the capture of weak reflected echo signals, AG-200A is equipped with automatic and manual gain functions, with a gain range of 0-80dB. In automatic gain mode, the instrument can automatically adjust the signal amplification factor according to the sound wave attenuation of the measured material, adapting to materials with different thicknesses and sound wave propagation characteristics; The manual gain mode allows users to manually adjust according to the actual measurement environment, improving signal clarity.
At the same time, the instrument adopts four detection methods: radio frequency (RF), positive half wave (POS), negative half wave (NEG), and full wave (FULL), which can optimize processing according to signal types, filter interference signals, and improve the stability of measurement data.
Probe adaptation and pulse matching
As the core component of ultrasonic transmission and reception, the performance of the probe directly affects the measurement effect. AG-200A supports both single crystal and twin crystal probes, and is compatible with multiple specifications and models (such as TS series twin crystal probes, DTM series single crystal probes, etc.). It also supports 20MHz high-frequency probes and can select the appropriate probe based on the thickness and material of the measuring material.
The pulse generator inside the instrument adopts a negative square wave emission design, and the pulse width and voltage can be automatically matched with the probe to ensure that the probe can stably emit ultrasonic pulses, while improving the consistency and reliability of the signal, laying the foundation for measurement.
Measurement of multi-layer material thickness
For measurement scenarios with multi-layer coatings or composite materials on the surface, AG-200A can achieve separate measurements of the thickness of each layer of multi-layer materials. The principle is to utilize the characteristic of ultrasonic waves reflecting at the interface of different media. When ultrasonic waves pass through multiple layers of materials, reflected echoes are formed at the upper and lower interfaces of each layer. The instrument identifies the time difference of echoes at different levels, combines the sound velocity parameters of each layer of material, calculates the thickness of each layer of material separately, and supports switching to display the thickness values of each layer under the same echo. It can measure the thickness of more than 10 levels.
Temperature compensation and corrosion, sediment measurement
In practical applications, temperature changes may affect the propagation speed of ultrasound in materials, leading to measurement errors. The temperature compensation function of AG-200A automatically corrects the sound velocity parameters by sensing the ambient temperature and material temperature, combined with preset temperature sound velocity correlation data, to offset the influence of temperature on measurement results.
For metal materials with internal corrosion or pipes with oxide layers or deposits on the inner wall, the instrument can visually present the internal structure of the material through B-scan mode. The B-scan mode is based on continuous ultrasonic pulse reflection signals, displaying thickness data at different positions in the form of images, which can clearly reflect the distribution and thickness of internal corrosion areas, oxide layers or sediments. Its principle is still to capture the reflection echoes of different interfaces and combine them with position positioning to achieve visual presentation.