Ultrasonic Thickness Gauge

Quick Answer: The Ultrasonic Thickness Gauge is a handheld non-destructive testing (NDT) instrument that measures the thickness of a material from one side by timing an ultrasonic pulse as it travels through the wall and back. An ultrasonic thickness gauge checks pipes, tanks, plates and vessels for corrosion or wear without cutting or dismantling them.

Pulse-Echo Measurement from One Side

The probe, or transducer, sends a short burst of high-frequency sound into the material. The sound travels to the far surface, reflects, and returns to the probe. The gauge measures the round-trip time and, using the speed of sound in that material, calculates thickness as velocity multiplied by time and divided by two. Because only one surface is needed, the inside of a pipe or tank can stay closed and in service.

Two settings govern accuracy. First, the sound velocity must match the material: steel, aluminium, cast iron, plastics and glass each carry sound at different speeds, and a gauge set for steel will misread aluminium. Second, the gauge should be zeroed and checked on a reference block of known thickness in the same material before each session. A couplant gel between probe and surface is essential, because even a thin air gap stops ultrasound from entering the part.

Rough, curved, painted or heavily corroded surfaces make readings harder. Clean a small spot where allowed, use a probe suited to small pipe diameters, and take several readings around each location. Thick paint adds to the apparent thickness unless the model has a mode designed to ignore coatings, which this title does not state. Maintenance teams often use the gauge alongside a vibration meter during plant condition surveys.

Specifications

Applications

• NDT training in mechanical, metallurgy and polytechnic labs
• Corrosion surveys of pipes, storage tanks and boiler shells
• Checking the remaining wall thickness of worn castings and ship plates
• Measuring glass and plastic sheet thickness where calipers cannot reach

Care & Handling

• Wipe couplant off the probe and the part after measuring; dried gel collects grit that scratches the probe face.
• Protect the probe cable from kinks and crushing, since most faults in field gauges start in the cable.
• Do not measure surfaces too hot for the probe unless it is rated for high temperature.
• Store the ultrasonic thickness gauge with its reference block, and test it on the block before each job.

Why Choose LabEquip

Engineering colleges with NDT teaching and plant-maintenance teams responsible for pipes and tanks are the usual buyers. LabEquip lists this gauge in General Lab Products; send the materials and thickness range you inspect through the contact page.

Frequently Asked Questions

Why is couplant gel necessary?

Ultrasound does not cross air gaps efficiently. The gel fills the tiny gap between probe and surface so the pulse enters the material. Without it, the gauge shows no reading or an unstable one.

What happens if the wrong material velocity is set?

Thickness is calculated from time and velocity, so a wrong velocity scales every reading. Set the velocity for the material, or calibrate on a sample of known thickness of that material.

Can it measure through paint?

Standard pulse-echo measurement includes the paint layer, and because sound travels more slowly in paint, it can overstate the metal thickness. Remove a small area of paint where permitted, or use a gauge with a coating-ignoring mode.

Can it measure plastic or glass?

Yes, if the correct sound velocity is set and the material transmits ultrasound well. Some plastics absorb high-frequency sound strongly, which limits the thickness that can be measured.

Why are readings unstable on a small pipe?

A flat probe face touches a curved surface only along a line, which weakens the echo. Use plenty of couplant, rock the probe gently to find the strongest steady reading, or choose a probe with a smaller face made for pipes.

Is the reading affected by temperature?

Yes. Sound velocity changes with material temperature, and ordinary probes can be damaged by hot surfaces. Measure near room temperature where possible, or use a high-temperature probe and couplant with a velocity correction.

Last Updated: September 2026