Sensitivity — Definition & NDT Use
The ability of an NDT method to detect discontinuities of a specified minimum size under defined conditions. Higher sensitivity means smaller defects can be detected. Sensitivity is affected by material properties, transducer characteristics, equipment settings, and technique. Standards specify minimum sensitivity requirements for different applications. Establishing sensitivity through reference standards ensures consistency and reliability of inspections.
From the inspector's bench, Sensitivity is run as a defined sequence: equipment verification on a known reference, scan setup against the procedure, scanning the part, and writing the indications into the report. A piezoelectric element converts the electrical pulse into a mechanical wave at the chosen frequency, transmits it into the part through couplant, and then converts the returning echo back into a voltage that the flaw detector digitises and displays on the screen. Procedure writing, inspector qualification, and the reference block establish the chain that lets a remote engineer trust an indication called a kilometre away from the office.
Sensitivity is selected when the failure mode the engineer cares about — surface crack, internal void, wall loss, lack of fusion — lines up with what the technique is physically capable of detecting.
ASME Section V Article 4
Ultrasonic examination methods for welds and components.
ASTM E114 / E164 / E2375
ASTM straight-beam, contact, and wrought-product UT practices.
ISO 16810 / ISO 16811
General principles and sensitivity setting for industrial UT.
The most expensive mistake with Sensitivity is treating it as a yes/no test rather than a characterisation — an indication called without a sizing strategy forces a repair where a fitness-for-service review might have left the part in service.
What does "Sensitivity" mean in NDT?
The ability of an NDT method to detect discontinuities of a specified minimum size under defined conditions. Higher sensitivity means smaller defects can be detected
Which standards govern the use of Sensitivity?
Sensitivity is most often referenced under ASME Section V together with the relevant ASTM practice or the matching ISO standard for the method; the contract or purchase order will name the controlling document and edition for any specific job.
What other NDT concepts should I read alongside Sensitivity?
The most directly related entries in this glossary are "scanning sensitivity", "resolution", "reference standard"; reading those together gives you the surrounding vocabulary used in inspection reports and procedures.