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Home > News > Why Ultrasonic Flaw Detector Calibration is Necessary?

Why Ultrasonic Flaw Detector Calibration is Necessary?

Oct. 09, 2022

Phased Array Ultrasonic Testing (PAUT), also known as Phased Array UT, is an advanced non-destructive testing technique that uses a group of ultrasonic testing (UT) probes made up of numerous small elements. Each of these is pulsed individually at timings calculated by a computer to create phased aspects of the process, while the array refers to the multiple elements that make up the PAUT system.

 

The phased array probe emits a beam that can be focused and swept electronically across the inspection piece without moving the probe itself. This is in contrast to single-element probes (also known as monolithic probes). These more conventional probes need to be physically moved or rotated to cover a larger area, whereas PAUTs do not.

 

Phased array ultrasonic inspection is based on wave physics principles and has applications in areas such as optical and electromagnetic antennas.


HS PA20-Ex Multi-function Phased Array Ultrasonic Flaw Detector

 HS PA20-Ex Multi-function Phased Array Ultrasonic Flaw Detector

 

You want to calibrate your ultrasonic flaw detector, but you don't know how.

 

Calibrating your ut flaw detector as a quality assessment professional is a skill that can bring many benefits, especially when it comes to the accuracy of your ultrasonic flaw detector. While you don't need to calibrate your ultrasonic flaw detector every day, the probability of accumulating errors after using your ultrasonic flaw detector consistently only means that it will be inaccurate for a long period of time. Therefore, for most NDT professionals, the importance of this process never goes away. The problem? This process is not well-known to most professionals. So, if you are experiencing the same challenges, then you are in luck because this article will provide you with all the necessary information you need to calibrate your ultrasonic flaw detector.

 HS PA30-E Ultrasonic Phased Array Detector

HS PA30-E Ultrasonic Phased Array Detector


Why do I need an ultrasonic flaw detector calibration?

There are many reasons for calibrating an ultrasonic flaw detector. However, the most important reason is that it ensures that the ultrasonic flaw detector is accurate. Ultrasonic flaw detectors tend to become slightly inaccurate when used for inspection but are still within acceptable tolerances. Over time, however, the cumulative margin of error increases, and the error can become large and outside acceptable tolerance levels. Regular calibration of your ultrasonic flaw detector will ensure that the margin of error is kept to a minimum and does not significantly affect the results of the detector.

 

Multi-function Phased Array Ultrasonic Flaw Detector HS PA20-Aex

Multi-function Phased Array Ultrasonic Flaw Detector HS PA20-Alex


What is ultrasonic flaw detector calibration?

Calibration involves setting up your measuring instrument using a standard unchanging reference to ensure the accuracy and precision of your measuring equipment. In the case of ultrasonic flaw detectors, this means adjusting them using a reference material that meets specific specifications. However, it usually occurs in two stages: manufacturer calibration and operator calibration. The manufacturer ensures that the flaw detector complies with the standard manufacturing specifications listed in the relevant specification. In contrast, user calibration is usually inspection specific and it ensures that the ultrasonic flaw detector conforms to the specifications of the defect that is expected to be detected.

 

Ultrasonic flaw detector calibration

The setup of an ultrasonic flaw detector calibration is usually accomplished in three different ways.

 

  • Zero offset calibration - this setting takes into account the time that the wave has elapsed before it enters the test sample and then equates this to the time it has elapsed as it passes through the test sample layer. This time is usually specified as t 0.


Actual Honeycomb Panel

 Actual Honeycomb Panel

 

  • Material velocity calibration - also known as the ultrasonic velocity setting, this calibration method is largely dependent on the material to be examined and the ambient temperature available during the setup. However, it expects some basic assumptions to be made before starting the calibration. These assumptions include elastic materials, frequencies below the size available in the test sample but high enough to establish the wavelength, constant atmospheric temperature and pressure, and non-diffusing materials.

 

  • Automatic calibration - This method requires specific settings to be made prior to calibration. These settings include the use of an ultrasonic velocity meter to adjust the material velocity values to be as close as possible to the actual values. In addition, the delay and zero offset values need to be set to zero. The method takes into account the velocity of two similar signal reflectors sending two separate signals from different distances.


In short, calibrating your ultrasonic flaw detector is not difficult. However, it is advisable to take care when calibrating your ultrasonic flaw detector as this will ensure that the calibration is accurate and that the detector is error-free. Also, ensure that you carry out this process regularly as over time minor errors in the readings can accumulate into a large number of errors. 


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