Ultrasonic thickness gaugeAs an important tool in industrial testing, its accuracy is directly related to equipment safety and production quality. However, in practical use, due to improper operation or misunderstanding, the following misunderstandings often occur, resulting in distorted measurement results or equipment damage. Here isUltrasonic thickness gaugeCommon misconceptions and analysis:

1、 Misconceptions about matching materials with sound velocity

Misconception: Failure to calibrate sound velocity based on material type, using default values directly (such as steel's sound velocity of 5920m/s).

Consequence: There is a significant difference in sound velocity between different materials (such as aluminum at about 6300m/s and copper at about 4700m/s). If the sound velocity of steel is used to measure aluminum, the thickness error can reach more than 10%.

The correct approach:

Refer to the material manual or use the instrument's "sound speed reverse measurement" function to input a known thickness value to infer the sound speed.

For composite materials or coating structures, it is necessary to set the sound velocity layer by layer or use a penetrating coating mode.

Misconception: Ignoring material anisotropy or temperature effects.

Case: When measuring castings or forgings, coarse grains cause fluctuations in sound velocity; The sound velocity of materials changes under high temperature conditions (such as a decrease of about 5% in sound velocity of steel at 500 ℃).

Suggestion:

For coarse-grained materials, use low-frequency probes (such as 2MHz) or electromagnetic ultrasonic thickness gauges.

When conducting high-temperature testing, use a high-temperature probe and refer to the temperature sound velocity correction table.

2、 Misunderstandings in the use of coupling agents

Misconception: Insufficient application or incorrect type of coupling agent.

Consequence: Air gaps cause attenuation of sound waves, resulting in measurement values that are too small or not displayed.

Correct operation:

Apply a uniform thin layer of couplant (such as glycerin, water-based gel) to avoid bubbles.

An increase in the amount of coupling agent is required for rough surfaces, or sandpaper should be used to smooth them out.

High temperature coupling agents (such as molten paraffin) are selected for high-temperature detection.

Misconception: Coupling agent contaminates the probe or material surface.

Case: The use of oil containing coupling agents in food grade pipeline inspection resulted in contamination.

Solution:

Choose non corrosive and easy to clean coupling agents (such as pure water, medical ultrasound coupling agents).

Clean the probe and material surface promptly after testing.

3、 Misunderstandings in probe selection and operation

Misconception: The probe frequency does not match the material thickness.

Rule:

Thin material (<1mm): Choose a high-frequency probe (such as 10MHz) to improve resolution.

Thick materials or rough surfaces: Choose a low-frequency probe (such as 2MHz) to enhance penetration.

Consequences of Error: High frequency probes attenuate quickly in thick materials, resulting in signal loss; The low-frequency probe has insufficient resolution for measuring thin materials.

Misconception: The probe is not vertically pressed against the surface of the material.

Impact: Oblique incidence causes the sound wave path to become longer and the measured value to be larger.

Operation points:

Keep the probe perpendicular to the surface and apply uniform pressure (to avoid deformation caused by excessive pressure).

For curved materials, use small-diameter probes or curved surface adaptation probes.

Misconception: Ignoring probe wear or contamination.

Case: Probe wear leads to sound wave divergence and large fluctuations in measurement values.

Maintenance suggestion:

Regularly check whether the probe chip is damaged and clean the surface stains.

Avoid collision between the probe and sharp objects, and use a dedicated protective cover when storing.

4、 Misunderstandings in measuring environment and surface treatment

Misconception: Direct detection in high temperature, strong electromagnetic field or corrosive environment.

Risk:

High temperature causes probe aging or material sound velocity changes.

Strong electromagnetic field interferes with instrument circuits and causes data jumps.

Corrosive gas corrodes the probe and instrument interface.

Response measures:

Use high-temperature probes or electromagnetic ultrasonic thickness gauges (without coupling agents, resistant to electromagnetic interference).

In corrosive environments, perform anti-corrosion treatment on instruments and probes (such as applying protective paint).

Misconception: Failure to clean the surface rust, paint or coating of materials.

Impact: The coating causes an extension of the sound wave path, resulting in larger measurement values; Loose rust layer leads to signal attenuation.

Handling method:

For thin coatings (<0.5mm), the instrument can automatically compensate; Thick coatings require polishing or the use of penetrating coating mode.

The severely corroded surface needs to be derusted first, and then tested with coupling agent.

5、 Misconceptions in Data Interpretation and Calibration

Misconception: Neglecting instrument calibration and zero point correction.

Consequence: Failure to calibrate leads to system errors (such as a deviation of 0.1mm in all measured values).

Calibration steps:

Use standard test blocks (such as V1 calibration block) for sound velocity and zero point calibration.

Regular calibration (recommended once a week) or calibration after each probe replacement.

Misconception: Blindly trusting the results of a single measurement.

The correct approach:

Measure multiple times (e.g. 3 times) at the same location and take the average.

For outliers, check the coupling status or probe position and remeasure.

Cross validation with other detection methods (such as eddy current thickness measurement).

Misconception: Failure to distinguish between actual thickness and displayed value.

Case: When measuring materials with grooves or holes, the instrument may display the thickness of adjacent areas.

Solution:

Move the probe to search for the maximum echo signal (corresponding to the real bottom surface).

For complex structures, use B-scan or C-scan imaging functions to assist in judgment.

6、 Misunderstandings in Maintenance and Storage

Misconception: The instrument has been idle for a long time without charging or stored in a humid environment.

Impact: Battery over discharge damage, circuit moisture and short circuit.

Maintenance suggestion:

When not in use for a long time, charge once a month and keep the battery level at 40% -60%.

Store in a dry, dark place to avoid drastic temperature changes.

Misconception: Use organic solvents to clean instrument casings.

Risk: Solvent corrosion of the outer shell coating or infiltration into the interior, damaging the circuit.

Cleaning method:

Wipe the outer shell with a dry cloth, and dip a small amount of neutral detergent in the stain area to wipe.

Avoid water or solvents from entering the probe interface or instrument gaps.