Long-Term Stability of the NIST Conical Reference Transducer

Area of Science:

• Materials Science
• Acoustics
• Metrology

Background:

• The National Institute of Standards and Technology (NIST) developed the Conical Reference Transducer (CRT) for advanced acoustic emission (AE) nondestructive testing.
• CRTs offer superior frequency response uniformity compared to conventional ultrasonic transducers.
• The CRT was commercially available from 1985 to 2000, supplied with detailed frequency-dependent sensitivity data.

Purpose of the Study:

• To assess the long-term stability of NIST Conical Reference Transducer (CRT) characteristics.
• To validate performance claims regarding the durability and reliability of CRTs over extended periods.
• To compare transducer sensitivity data from 1985 with measurements taken in 2009.

Main Methods:

• Eight NIST CRTs, stored under controlled laboratory conditions since 1985, were re-tested in 2009.
• Transducer sensitivity was measured as a function of frequency (volts per micrometer of normal displacement).
• Sensitivity data from 1985 and 2009 were statistically compared.

Main Results:

• The 2009 sensitivity measurements showed remarkable agreement with the original 1985 data for the tested CRT units.
• This consistency confirms the minimal degradation of transducer performance over 24 years.
• The results directly support the manufacturer's claim of expected service life of decades with proper care.

Conclusions:

• The NIST Conical Reference Transducer (CRT) exhibits exceptional long-term operational stability.
• Proper storage and handling ensure that CRTs maintain their high-performance characteristics for many years.
• These findings are crucial for the continued reliable application of CRTs in acoustic emission nondestructive testing.