What is an acoustic emission sensor? What is the principle and types of AE sensors?
Brief：Acoustic emission sensors are made of the principle that the physical properties of certain substances (such as semiconductors, ceramics, piezoelectric crystals, strong magnetic bodies and superconductors) change with the action of the outside world to be measured (piezoelectric effect). The piezoelectric element of the acoustic emission sensor can convert the tiny displacement of the material surface into a voltage signal through the piezoelectric effect. Acoustic emission sensor is mainly divi
Acoustic emission (AE) sensors are the transducers converting the received acoustic waves motion on the surface into measurable electrical signals. The input function of the AE sensor can be force, displacement or speed and the output is analog voltages. The sensitivity of the AE sensor is commonly expressed in volts per meter per second or volts per microbar.
There are a few main common AE sensor types:
- Resonant sensors: the most commonly used AE sensor with high sensitivity at certain frequency ranges;
- Wideband sensors: wider frequency bandwidth. Suitable to researches to obtain the full spectrum of the AE events in the unknown material or tests in order to find out the most interested frequency range. But the sensitivity is typically flat and lower than the resonant sensors;
- High temperature sensors: suitable for high temperature contact surface;
- Differential sensors: suitable for noisy environments;
- Other sensors: miniature sensors and others.
In the practical application of AE, a large number of metal structures with stable structure, such as pressure vessels, are encountered. In such applications, an AE sensor with resonance frequency of 150kHz is often used to receive AE signals. For corrosion, leakage and other AE signals, resonant sensors with resonant frequency of 40kHz are used.
Bandwidth and sensitivity are a pair of contradictory indicators. The wider the bandwidth, the lower the sensitivity. Narrow band is easier to obtain higher sensitivity and the final purpose of application is high sensitivity. Broadband sensor should be used in principle for spectral analysis because its response sensitivity is relatively flat in a wide frequency band.
