1. Ultrasonic thickness gaugePreparation of operating instruments and parameter settings

Probe selection: Choose the appropriate probe based on the type of material being tested (such as metal, plastic, composite material) and surface condition (roughness, curvature). For example, small curvature radius pipelines require a specialized probe with a small diameter of 6mm, while castings require a low-frequency probe with a frequency of 2.5MHz.

Sound speed preset: Input the longitudinal wave sound speed of the tested material (such as steel 5920m/s, aluminum 6305m/s). If the material is unknown, the sound velocity can be measured back using a standard test block.

Environmental adaptation: High temperature environments (≤ 300 ℃) require the use of heat-resistant coupling agents and high-temperature probes to avoid damage to ordinary probes.

2. Instrument calibration (two-point calibration method)

Selection of test blocks: Select two standard test blocks that are consistent with the material, sound velocity, and curvature of the tested material, with thicknesses close to the lower limit (such as 5mm) and upper limit (such as 50mm) of the measurement range.

Calibration steps:

Disable the minimum value capture function and delete old calibration data.

Apply coupling agent to the surface of the test block and vertically attach the probe to the test block.

Measure the thin test block and adjust the instrument display value to the standard value; Repeat the measurement of the thick test block and correct the high-end error.

After completing the calibration, save the data and enter measurement mode.

Key point: Before calibration, it is necessary to ensure that the contact surface of the probe is smooth, and worn probes need to be polished or replaced with 500 # sandpaper.

3. Surface treatment of the tested workpiece

Clean the surface: Remove oil stains, rust, oxide layers, and paint to expose a metallic luster. Rough surfaces can be reduced in roughness by sanding with sandpaper.

Coupling agent selection:

Smooth surface: Low viscosity coupling agent (such as water, glycerol).

Rough/Vertical Surface: High viscosity coupling agent (such as butter, water glass).

High temperature workpiece: Apply temperature resistant coupling agent to the probe.

Coupling requirements: The coupling agent should cover the contact surface of the probe, and the stable display of the coupling mark indicates good contact; If the logo flashes, it needs to be reapplied.

4. Measurement operations and techniques

Single point measurement method: Measure twice with a probe at one point, with the probe dividing surfaces at 90 degrees to each other, and take the smaller value.

30mm multi-point measurement method: When the measurement value is unstable, take multiple measurements within a 30mm diameter circle centered on the measurement point and take the minimum value.

Continuous measurement method: Measure continuously along the designated route with an interval of ≤ 5mm, and record the minimum value.

Grid measurement method: Draw a grid in a designated area, measure the thickness at each point and record it, suitable for corrosion monitoring of high-voltage equipment.

Pipe measurement techniques:

Large pipe diameter: measured perpendicular to the axis direction.

Small tube diameter: Measure along the axis and perpendicular axis direction, and take the minimum value.

　　5. Ultrasonic thickness gaugeData Processing and Error Prevention

Data recording: Record the location of measurement points, thickness values, and environmental conditions (temperature, humidity).

Error analysis:

Surface roughness: Rough surfaces result in poor coupling, requiring polishing or the use of high viscosity coupling agents.

Curvature radius: Special probes are used for small curvature pipes to avoid point contact.

Internal defects of the material, such as inclusions and interlayers, with a displayed value of approximately 70% of the nominal thickness, require further testing with a flaw detector.

Temperature effect: For every 100 ℃ increase in the temperature of the hot material, the sound velocity decreases by 1%. It is necessary to adjust the sound velocity or use a high-temperature probe.

Stacked material: only measures the thickness of the layer in contact with the probe, and cannot penetrate the uncoupled space.

Maintenance suggestion:

Avoid strong electromagnetic interference, prevent probe wires from bending and chemical corrosion.

Clean the probe after use (wipe with alcohol), and remove the battery when not in use for a long time.