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Multi-Channel EMAT System

 

System Features

The Electro-Magnetic Acoustic Transducer (EMAT) system is a computer controlled multi-channel electronic system used to operate EMAT transducers for couplant-free transmitting and receiving of oblique incident bulk ultrasonic waves and guided waves in ferromagnetic materials.

The system serves as signal-generating and -processing component.  It provides the time delayed RF signals for transmitter stages, amplification, filtering and summation of the received signals and the power supply of the electromagnets of the transducers.

System control, such as frequency, beam angle, pulse length (number of cycles), pulse repetition rate, probe selection, etc., is performed by the system setup program.
System Characteristics 

   Base Unit

  • Synthesizer board

  • Burst generator board (frequency range: 0.4 2.0MHz); burst length (number of cycles) and frequency are adjustable via PC

  • Two transmitter power stages

  • Receiver board with two delayed receiver channels (time delay of all channels can be modified separately)

  • Output amplifier and video unit

  • Control PC for system control and parameter settings

  • Power supplies

The burst generator produces burst signals with a center frequency given by the synthesizer. These signals are digitally delayed, then amplified by the driver stages and transmitted to the transducer(s).

Signals received from the receiver coils are pre-amplified in the transducer by built-in preamplifiers and transmitted to the system. There, the signals are further amplified and filtered by the filter stages and are then time delayed. After the combination unit, the received RF signals are summarized and transmitted to the video output. At this stage, it is possible to choose between RF output and video output.

       Technical Data
Frequency Range:

Burst Duration:
Pulse Repetition Rate:
Time Delay:

Amplification:

0.4 - 2.0MHz, adjustable in 10kHz steps
(2.0MHz upper 3dB cut-off frequency
1 - 15 cycles, adjustable in steps of 1
2.5 - 20ms, adjustable in 1s steps
0 - 10s, adjustable in 2ns steps (transmitter) 
0 - 1.5s, adjustable in 25ns steps (receiver)
Maximum of 50dB; 40dB adjustable in 255 steps 

   Magnetization  Unit

The Magnetization Unit provides the AC power for the transducers and consists of an electromagnet. Amplitude and frequency of the magnetization are adjustable. Only transducers with permanent magnets are operated by the Base Unit.

The components of the Magnetization Unit are:

  • Frequency generator and a synchronization board for synchronizing the trigger signal of the Base Unit with AC current for the transducer(s) electromagnet

  • LF amplifier for amplification of AC current for magnetization

     Computer Controlled Parameters and Functions 
  • Trigger Mode: internal, external, software triggered

  • Pulse Repetition Rate

  • Ultrasonic frequency

  • Number of cycles/bursts

  • Time Delay for each transmitter/receiver channel

  • Filter selection: 0.4 - 1.3MHz, 0.4 - 2.0MHz

  • Adjustment of receiver amplifier


Information Request FormEMAT-1 Technical Data

 
 

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Last modified: June 25, 2015