How do you calibrate and verify your ultrasonic equipment for accurate measurements?

1 Choose the right probe

The first step is to select the appropriate probe for your ultrasonic testing. Probes come in different sizes, shapes, frequencies, and angles, depending on the type and location of the defect you want to detect. For example, you might use a straight beam probe for thickness measurement, a dual element probe for near-surface defects, or an angle beam probe for weld inspection. Make sure the probe is compatible with your ultrasonic device and has no visible damage or wear.

2 Connect and set up the device

The next step is to connect the probe to the ultrasonic device and turn it on. You might need to adjust some settings on the device, such as the pulse voltage, the gain, the range, the filters, and the display mode. Refer to the manufacturer's manual for the recommended values and procedures. You should also check the battery level and the cable connections to ensure proper operation.

3 Perform a functional test

Before you start calibrating your ultrasonic equipment, you should perform a functional test to verify that it is working correctly. A functional test involves sending a pulse through a known reference material, such as a calibration block, and observing the signal on the screen. You should see a clear and stable echo from the reference material, with no distortion or noise. If the signal is weak, noisy, or erratic, you might need to troubleshoot your equipment or replace some components.

4 Calibrate the time base

The time base is the scale that shows the distance or depth of the defect on the screen. To calibrate the time base, you need to use a calibration block with known dimensions and features, such as holes, notches, or steps. You should place the probe on the calibration block and align it with the feature you want to measure. Then, you should adjust the range and the velocity settings on the device until the echo from the feature matches the expected value on the screen. You should repeat this process for different features and probe angles to ensure accuracy.

5 Calibrate the sensitivity

The sensitivity is the level of amplification of the signal on the screen. To calibrate the sensitivity, you need to use a calibration block with known reflectors, such as flat-bottom holes or side-drilled holes. You should place the probe on the calibration block and align it with the reflector you want to measure. Then, you should adjust the gain setting on the device until the echo from the reflector reaches a certain percentage of the screen height, usually 80%. This is called the reference level. You should repeat this process for different reflectors and probe angles to ensure consistency.

6 Verify the calibration

The final step is to verify that your ultrasonic equipment is calibrated correctly and ready for use. You should use a verification block with unknown defects, such as cracks, voids, or inclusions. You should place the probe on the verification block and scan it for defects. You should compare the results with the expected values from the verification block certificate or report. You should also check the repeatability and reproducibility of your measurements by performing them several times or with different operators. If your measurements are accurate and consistent, your ultrasonic equipment is calibrated and verified.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?