Article Article
2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.



ASTM, 2015, ASTM E797/E797M: Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo Contact Method, ASTM International, West Conshohocken, PA.

Bhowmick, S., 2011, “Ultrasonic Inspection for Wall Thickness Measurement at Thermal Power Stations,” International Journal of Engineering Research & Technology, Vol. 1, pp. 89–107.

Boateng, A.N.K.A., E.K. Diawuo, S.Y. Adzaklo, D.K. Awuvey, P.N.K.N. Agyei, E.Y. Amoakohene, and E. Kwaasi, 2015, “Ultrasonic Thickness Gauging as a Means of Evaluating Integrity of Liquefied Petroleum Gas Vessels,” Journal of Science, Technology, and Environment Informatics, Vol. 2, No. 2, pp. 36–41.

Cal Tech, 2019, “Camera Calibration Toolbox for Matlab,”, accessed: November 2019.

Cheong, Y.-M., K.-M. Kim, and D.-J. Kim, 2017, “High-Temperature Ultrasonic Thickness Monitoring for Pipe Thinning in a Flow-Accelerated Corrosion Proof Test Facility,” Nuclear Engineering and Technology, Vol. 49, No. 7, pp. 1463–1471,

Fowler, K.A., G M. Elfbaum, and T.J. Nelligan, 1997, “Theory and Application of Precision Ultrasonic Thickness Gaging,” Olympus Industrial Resources, accessed at

Hellier, C., 2020, Handbook of Nondestructive Evaluation, 3rd edition, McGraw-Hill Education.

ISO, 2017, ISO 16809:2017, Non-destructive testing – Ultrasonic thickness measurement, International Organization for Standardization, Geneva, Switzerland.

Lebowitz, C.A., and L.M. Brown, 1993, “Ultrasonic Measurement of Pipe Thickness,” Review of Progress in Quantitative Nondestructive Evaluation, Vol. 12, pp. 1987–1994.

Liu, H., L. Zhang, H.F. Liu, S. Chen, S. Wang, Z.Z. Wong, and K. Yao, 2018, “High-Frequency Ultrasonic Methods for Determining Corrosion Layer Thickness of Hollow Metallic Components,” Ultrasonics, Vol. 89, pp. 166–172,

Markucic, D., V. Krstelj, and A. Lypolt, 2007, “Accreditation of Ultrasonic Thickness Measurement Methods – Practical Aspects,” 5th International Conference on Certification and Standardization in NDT, Berlin, Germany.

Nelligan, T., 2019, “An Introduction to Ultrasonic Thickness Gaging,” Olympus Industrial Resources, accessed at

Raj, B., T. Jayakumar, and M. Thavasimuthu, 2002, Practical Non-Destructive Testing, second edition, Woodhead Publishing Ltd., Cambridge, England.

Rao, J., M. Ratassepp, and Z. Fan, 2017, “Quantification of Thickness Loss in a Liquid-Loaded Plate Using Ultrasonic Guided Wave Tomography,” Smart Material Structures, Vol. 26, No. 12,

de Andrade Silva, B.C., M.S. Motta, and J.E.F. de Oliveira, 2013, “Development of a Methodology to Determine Thickness Measurement Uncertainties by Ultrasonic Test in Aerospace Parts,” Materials Science Forum, Vol. 758, pp. 89–97.

Smith, S.W., 1997, The Scientist and Engineer’s Guide to Digital Signal Processing, California Technical Pub, San Diego, CA, pp. 436–442.

Tesfaye, T., M. Siddig, and K. Ki-Seong, 2019, Mapping of Ultrasonic Thickness Measurements Using Laser Grid Projection and Image Processing,” Insight – Non-Destructive Testing and Condition Monitoring, Vol. 61, No. 11, pp. 643–649,

Turcotte, J., P. Rioux, and J.-A. Lavoie, 2016, “Comparison Corrosion Mapping Solutions Using Phased Array, Conventional UT and 3D Scanners,” 19th World Conference on Non-Destructive Testing, Munich, Germany, 13–17 June.

Waag, G., L. Hoff, and P. Norli, 2015, “Air-Coupled Ultrasonic Through-Transmission Thickness Measurements of Steel Plates,” Ultrasonics, Vol. 56, pp. 332–339,

Willey, C.L., 2016, “Ultrasonic Guided Wave Tomography for Wall Thickness Mapping in Pipes,” Ph.D. thesis, University of Cincinnati, Cincinnati, OH.

Yassen, Y., M.P. Ismail, A.A. Jemain, and A.R. Daud, 2011, “Reliability of Ultrasonic Measurement of Thickness Loss Caused by Corrosion,” Insight: Non-Destructive Testing and Condition Monitoring, Vol. 53, No. 12, pp. 658–663.

Yi, W.-G., M.-R. Lee, J.-H. Lee, and S.-H. Lee, 2006, “A Study on the Ultrasonic Thickness Measurement of Wall Thinned Pipe in Nuclear Power Plants,” 12th Asia–Pacific Conference on NDT, 5–10 November, Auckland, New Zealand.


Usage Shares
Total Views
97 Page Views
Total Shares
0 Tweets
0 PDF Downloads
0 Facebook Shares
Total Usage