Æmission is a fast digitizer/recorder (1.25MSps@18bit or 5MSps@16bit) specifically designed for the acoustic emission investigation.
Thanks to the long lasting collaboration with the Polytechnic University of Turin, patented algorithms have been implemented in the internal FPGA.
Æmission can process the aemission waves locally extracting the tipical parameters of interest (βt, b-value, cumulative count)
Æmission is working in a large sperimental project founded by Regione Toscana named MONFRON
Acoustic Emission (AE) is the phenomenon of radiation of acoustic (elastic) waves in solids as result of damage or irreversible change in the internal structure of the material. Although the name itself suggests an audible signal, this is misleading, because the range of the involved frequencies is between 50Khz up to 1Mhz, pratically ultrasonic frequencies.
Typically the release of elastic energy and so the AE occours as result of cracks due to external forces (mechanical loading) or conditions (aging, temperatures).
Acoustic Emission is a very powerful method of investigation applied to the structural health monitoring.
Major application of AE technique are:
- Localization of cracks inside the material
- Cracks evolution (stable or dangerous)
- State of Health monitoring (predictive alarms)
Æmission is supplied with 8 piezoceric sensors, the sensing element has been selected and characterized together with the Polithecnic University of Turin for better suit the civil structure monitoring and to get the most appropriate signals.
Sensors are placed around the zone to be monitored and connected to the Æmission via 10 meters cables .
Æmission BLOCK DIAGRAM
Analog signals, coming from the piezoceramic sensors are first hardware conditioned and level adapted by a cascade of analog filters before they can be converted into the digital world.
Eight high speed ADCs (1.25MSps@18bit or 5MSpsp@16bit) convert continuosly the analog signal into digital, synchronized to the same clock source.
Digital signals are then parallel acquired and processed by the FPGA and, according the defined parametrization, only the events that satisfy the setting condition are transferred to the Linux CPU.
Inside the Linux CPU events are stored locally and can be shared remotely by WiFi or 3.5G connection.
The integrated GNSS receiver can synchronize more Æmission units; virtually a limitless number of acoustic sensors can be acquired.
4-channel Æmission board
After a reasonable period of monitoring, are available the plots of the parameters useful to understand the nature of the cracking and to give an interpretation to the structure under monitoring.
The following graph represent an ongoing monitoring in a marble quarry.
In order are represented:
- AE cumulative count
- Frequency of events
- Amplitude of events
A 3D graph of the emission sources is represented in the below graph
Blue squares are the AE sensors, red dots rappresent the localization of the sources of emissions.