Technical terms
Material Velocity (Material Calibration): The speed at which sound waves travel through a given material. Each material has a specific velocity, which the gauge uses to calculate thickness by multiplying the velocity by the measured time and dividing the result by two. Accurate calibration requires setting the correct sound velocity for the test material. Since velocity changes with temperature, it's important to calibrate the gauge close to the temperature of the measurement environment.
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Pulse-Echo Measurements: In this mode, the transducer emits an ultrasonic pulse that reflects off the back wall of the material and returns. The time delay is used to calculate the total thickness—from the probe to the far wall.
When coatings are present, the total thickness (coating + base material) is measured. Since most coatings have a much lower sound velocity (often < 50%), thicker coatings can significantly affect accuracy.
Direct-contact transducers also have a larger near-surface dead zone, reducing their precision in thin wall applications.
Echo-Echo Measurements: This mode measures the time between two backwall echoes, ignoring the coating layer. It provides a more accurate base material reading when coatings are present. Echo-Echo requires a high-damping transducer and is limited in minimum and maximum measurable wall thickness compared to Pulse-Echo mode.
Echo-Echo-Verify measurements: Also known as triple echo mode, it uses additional echoes to confirm measurement accuracy, ideal for applications requiring meticulous data validation.
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High-Speed Scan Mode: Enables rapid scanning across large areas with up to 140 measurements per second. The display refreshes at 25 Hz, helping to detect minimum thickness points efficiently.
Limit Alarm Mode: Set high and low threshold limits to receive visual and audible alerts when measurements fall outside the acceptable range. Ideal for quick quality control.
Differential Mode: Shows the deviation from a user-defined nominal value. This feature is essential for monitoring manufacturing tolerances and identifying material loss or corrosion.
Velocity Gauge (VX Mode): Converts the gauge into a dedicated velocity meter, displaying speed of sound in m/s. Useful for basic material characterisation such as nodularity or hardness testing based on velocity values.
Adjustable Gain: The TI-PVX series offers flexible signal amplification via Manual Gain, Automatic Gain Control (AGC), and Time Dependent Gain (TDG), ensuring echo visibility across varying materials and wall thicknesses.
Time Dependent Gain (TDG): In Echo-Echo or Echo-Echo-Verify modes, echo amplitudes naturally decay over time. TDG compensates for this by gradually increasing gain, maintaining consistent echo visibility for more accurate readings.
Gates: A Gate is an adjustable marker in the time line of a measurement used to evaluate specific parts of the echo signal from the material being tested. It helps to focus on an area and skip false echo's that disrupt the measurement The TI-PVX is equiped with up to 3 gates that can be fine tuned to accommodate a variety of applications.
