Abstract: A transmitting and receiving switch assembly for an electromagnetic acoustic transducer (EMAT) and a method for selectively switching an EMAT between transmit mode and receive mode both use a particular circuit. This circuit contains an EMAT coil coupled to a tuning capacitor, which allows the EMAT to be operated at a desired frequency when transmitting. A set of capacitors separates the EMAT coil from a set of diode strings (preferably containing at least one fast switching silicon diode), which are joined by a resistive connection. A transformer, which is center tapped at its primary winding, is coupled to the other end of the diode strings. Finally, a receiver input is connected to the transformer. In operation, the frequency of the EMAT is set by appropriately energizing and tuning the tuning capacitor. A voltage is then applied in the center tapped transformer and in the resistive link between the diode strings.

Abstract: A method for non-destructively testing closely-spaced objects, such as header tube stubs for a furnace or boiler using electromagnetic acoustic transducers (EMATs) having meander coil sensors. The small size of the sensor combined with the need to move the sensor only a small fraction of the circumference of a tube to scan the entire circumference of the tube under test permits easy and accurate testing of an entire tube, even when the tube is one of a closely-spaced bundle.

Abstract: A variable power source is provided having multiple power modules each of which can produce a portion of the total range of voltage required for pulsed operation of an electromagnetic acoustic transducer electromagnet. The power modules are connected in series, and controlled by individual potentiometers which are simultaneously adjusted. Selector switches are provided for enabling or disabling each module. The output of the power modules is connected to a pulser/controller for wave forming prior to sending the output signal to the electromagnet. A noise filter can be placed between the power modules and the pulser. LED-type indicators on the selector switches may be used to indicate the operational status of the modules.

Abstract: An acoustic emission leak simulator (10) for a nondestructive simulation of a leak in a structure employs a fluid supply with variable orifice (18) for controllably releasing the fluid to create a simulated leak source (20). An acoustic waveguide (22) acoustically coupled to the variable orifice (18) couples the sound waves into the structure (12) for simulation of a leak signal. Transducer (30) positioned at a predetermined distance from the simulated leak source (20) characterize the leak signals for a leak detection system.