Full analysis of the usage details of ultrasonic thickness gauge
1、 Preparation before use
1. Instrument inspection
-Appearance and Function: Confirm that the instrument has no physical damage, the screen display is normal, the button response is sensitive, and the battery level is sufficient (recommended battery level>20%). If it is a split type instrument, it is necessary to check whether the connection between the host and the probe is stable, and whether the interface is free of oxidation or corrosion.
-Probe status: Check whether the contact surface of the probe is worn or adhered with impurities. If necessary, clean it with an alcohol swab to avoid scratches that may affect the coupling effect.
-Calibration verification: Check the previous calibration record after turning on the device. If the ambient temperature and humidity change by more than 10% or if the probe is replaced, recalibration is required (see calibration process).
2. Preprocessing of the tested object
-Surface cleaning: Remove oil stains, rust, coatings, etc. from the test area, with a roughness of<10 μ m (sandpaper can be used to polish to a bright finish).
-Curvature matching: If the workpiece is a curved surface, priority should be given to selecting a probe that matches the nominal curvature (such as a Φ 10mm probe adapted to a pipeline), or manually compensating for curvature errors after calibration with a flat test block.
2、 Measurement operation steps
1. Selection and application of coupling agent
-Type matching: Common coupling agents include engine oil (universal type), glycerin (sensitive material), and water (non corrosive occasions). Priority should be given to using engine oil for cast iron and steel; Soft metals such as aluminum and copper can be protected against corrosion with glycerin.
-Dosage control: Drop a small amount of coupling agent on the contact surface of the probe to cover the area in a transparent film shape. Excessive use may cause sound wave attenuation or overflow to contaminate the workpiece.
2. Probe placement and measurement
-Vertical incidence: Place the probe axis perpendicular to the surface of the workpiece to avoid tilting (angle compensation function is required when the angle error is greater than 5 °).
-Uniform pressure: Apply about 1-2N of pressure (feels like touching a keyboard). Excessive pressure may cause readings to be too small, while insufficient pressure may result in poor coupling.
-Multi point measurement: Take the average of at least 3 measurements in the same area, with a plane spacing of>10mm, and evenly distribute measurement points along the circumference of the curved surface.
3. Data reading and recording
-Stable reading: Record after the screen value stabilizes (usually 3-5 seconds), and the jumping range should be<± 0.02mm.
-Environmental labeling: Simultaneously record temperature, humidity, workpiece material, and surface condition (such as "Q235 steel plate, 25 ℃, sandblasting treatment").
-Exception handling: If the reading suddenly changes or continues to fluctuate, check if the coupling agent is dry and if the probe is loose, and recalibrate if necessary.
3、 Environmental and operational influencing factors
1. Temperature control
-The working temperature of the instrument should be between 0-40 ℃. Low temperatures (<-10 ℃) may cause delayed response of the LCD screen, while high temperatures (>50 ℃) should avoid direct sunlight and shorten the single measurement time.
-When the temperature difference between the tested workpiece and the environment is greater than 10 ℃, it needs to be allowed to stand until thermal equilibrium (about 15 minutes) before measurement.
2. Electromagnetic interference avoidance
-Stay away from strong magnetic field equipment such as frequency converters and motors for more than 2 meters, and turn off potential sources of interference such as mobile phones and wireless devices.
-Connect the probe with a shielded wire, and if the signal noise is significant, enable the instrument filtering function (such as Davis gate control).
3. Adaptation to workpiece characteristics
-Thin piece measurement: When the thickness is less than 1mm, use a high-frequency probe (such as 10MHz) and shorten the measurement time to prevent overheating damage.
-Multi layer structure: When encountering a combination of anti-corrosion layer and substrate, it is necessary to first test the difference in sound velocity, and if necessary, use a dual crystal probe to separate the interface.
4、 Data Management and Reporting
1. Storage specifications
-The instrument memory data needs to be exported regularly (such as USB backup), and the file name should include information such as date, workpiece number, and measurement person.
-Paper records should include traceability information such as location diagrams of measuring points, instrument models, calibration validity periods, etc.
2. Uncertainty analysis
-Typical sources of error: coupling agent thickness (± 0.01mm), sound velocity setting error (± 1%), probe wear (replacement required when>10 μ m).
-It is recommended to keep the final result to two decimal places, such as "Thickness: 5.23 ± 0.05mm (k=2)".
5、 Maintenance and troubleshooting
1. Daily maintenance
-After measurement, wipe off the residual coupling agent of the probe with a dust-free cloth and store it in a moisture-proof box (humidity<60%).
-Check the oxidation status of battery contacts every month, and remove the battery leak proof liquid if not in use for a long time.
2. Simple troubleshooting
-No display: Check the power switch and fuse (some models are equipped with them);
-Weak signal: Replace the coupling agent, polish the surface of the workpiece, or increase the gain;
-Calibration failure: After resetting to factory settings, recalibrate. If the issue persists, contact the manufacturer.
6、 Safety and Standards
-Electrical safety: Avoid working outdoors on rainy days, and probe cables must not come into contact with exposed wires.
-Chemical protection: Wear nitrile gloves when using corrosive coupling agents (such as hydrochloric acid) and clean the skin contact area in a timely manner.
-Standard compliance: Refer to GB/T 4957-2003 "Ultrasonic Thickness Measurement Method" or ASTM E799-14 for calibration and measurement.