Machine Design

Measuring thickness with sound

Ultrasound provides an accurate and reliable method of gauging part thickness, but it can be complicated.

Engineers at Agfa NDT, Lewistown, Pa. (, have simplified the process with the CL 400 Ultrasonic Precision Thickness Gauge. It can use contact, delay, and bubbler probes and displays thickness values in large, easy-to-read digits.

The probes emit ultrasonic signals into the part being measured, some of which are reflected back when they hit the other side of the part. The unit detects returning signals and computes part thickness. An alarm bar graph shows when measurements fall outside user-programmable limits.

Measurements have user-adjustable resolutions, which go all the way down to 0.0001 in., or 1 micron. A bidirectional RS-232 port lets users upgrade gage software over the Internet, send up to 250 files with 10,000 readings to a PC, and transfer custom parameter setups. Parameters can include material type and grade, part name and description, alarm values, and calibrated settings.

The device can be powered by "AA" alkaline, NiMH, and NiCd batteries or an ac power supply. A durable, impact-resistant, gasket-sealed plastic housing protects the hardware. The device can also be upgraded by adding an A-Scan or data recorder. A-Scan helps align the transducer and verifies measurement accuracy while the recorder provides hardcopy of thickness values.


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