Significance and Use
Degradation in sensor performance can occur due to dropping, mechanical shock while mounted on the test structure, temperature cycles, and so forth. It is necessary and desirable to have a simple measurement procedure that will check the consistency of sensor response, while holding all other variables constant.
While test blocks of many different kinds have been used for this purpose for many years, an acrylic polymer rod offers the best all-around combination of suitable acoustic properties, practical convenience, ease of procurement, and low cost.
Because the acoustic properties of the acrylic rod are known to depend on temperature, this practice requires that the rod, sensors, and couplant be stabilized at the same working temperature, prior to application of the practice.
Attention should be paid to storage conditions for the acrylic polymer rod. For example, it should not be left in a freezing or hot environment overnight, unless it is given time for temperature stabilization before use.
Properly applied and with proper record keeping, this practice can be used in many ways, such as:
To determine when a sensor is no longer suitable for use.
To check sensors that have been exposed to high-risk conditions such as dropping, overheating, and so forth.
To get an early warning of sensor degradation over time.
To obtain matched sets of sensors and preamplifiers.
To verify sensors quickly but accurately in the field, and to assist troubleshooting when a channel does not pass a performance check.
1.1 This practice is used for routinely checking the sensitivity of acoustic emission (AE) sensors. It is intended to provide a reliable, precisely specified way of comparing a set of sensors or telling whether an individual sensor's sensitivity has degraded during its service life, or both.
1.2 The procedure in this practice is not a “calibration” and does not give frequency-response information.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This practice does not purport to recommend one sensor manufacturer over another nor does it imply that one type of sensor will react differently from another when using this procedure.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.