Portable electromagnetic acoustic transducer pulser controller

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.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to the field of non-destructive 
testing and in particular to controlling the magnet of an electromagnetic 
acoustic transducer with a novel switching circuit. 
2. Description of the Related Art 
Electromagnetic acoustic transducers are commonly used to non-destructively 
test welds and materials in environments, such as industrial furnaces and 
boilers, where visual or physical inspection does not reveal defects. 
Electromagnetic acoustic transducers can be placed or sent into areas 
where larger testing equipment cannot obtain access as well. 
The magnetic field required by an electromagnetic acoustic transducer 
sensor may be supplied by a rare earth permanent magnet or an 
electromagnet. When the application requires a pulsed electromagnet, a 
switching circuit is necessary to provide the pulsing. The design of the 
magnet determines the field strength (the current level), voltage, pulse 
width, pulse repetition rate, and other parameters which influence the 
inspection capabilities of the electromagnetic acoustic transducer. 
Field inspections require that equipment be portable, lightweight, and 
reliable, as well as capable of providing the necessary current and 
voltage for operation. Prior known switching control equipment consists of 
large, heavy (150 lbs or greater) laboratory equipment which uses a 480 
VAC power source. In many cases, this equipment is too bulky and does not 
fit into the areas which are to be inspected, such as through the man-ways 
of boilers. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a small, portable 
electromagnetic acoustic transducer magnet pulser which can be easily 
transported and used in field inspections. 
It is a further object of the invention to provide a switching control 
circuit for a power source of a pulser for an electromagnetic acoustic 
transducer electromagnet which can deliver between 0 and 200 VDC. 
Accordingly, a pulser and switchable power source system are 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 modules are connected in series, 
and controlled by individual potentiometers which can be simultaneously 
adjusted by an operator. 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. 
Optionally, a noise filter can be placed between the power modules and the 
pulser. LED-type indicators on the switches may be used to indicate the 
operational status of the modules as well. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawing and descriptive matter in which a 
preferred embodiment of the invention is illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawing, a variable DC power source 10 according to 
the invention is connected to a pulser 90 for driving an electromagnetic 
acoustic transducer electromagnet 100. The pulser 90 can be any known type 
of pulse forming circuit for shaping the output signal of the variable DC 
power source 10 before it is delivered to the electromagnet 100. Power is 
supplied to the variable DC power source by a standard 110 VAC supply 120, 
such as from a wall outlet. 
Variable power source 10 has variable power modules 20a-20d connected in 
series. The power modules 20a-20d have diodes 26a-26d placed across the 
positive terminals 22a-22d and negative terminals 24a-24d of each module 
20a-20d, respectively. The diodes 26a-26d are oriented to provide reverse 
voltage protection for each module, that is the cathode of each diode 
26a-26d is connected to the positive terminals 22a-22d. 
A ganged potentiometer 32 is used to simultaneously control the magnitude 
of the output voltage of the power modules 20a-20d. Ganged potentiometer 
32 has individual sections 30a-30d for controlling each power module 
20a-20d. Each section 30a-30d is connected to one of the power modules 
20a-20d using a bus or other standard connector 34. Shielded wires may be 
used as well. 
Module selectors 60a-60d are connected to control jumper block 70 for 
enabling or disabling power modules 20a-20d. Each selector 60a-60d has a 
switch 66 and may have an LED 62 and current limiting resistor 64 in 
series on the enabled, or ON side of the switch 66. Control jumper block 
70 is an integrated portion of power modules 20a-20d, although the jumper 
block 70 is shown detached from the modules 20a-20d in the drawing. Jumper 
block 70 as shown has 12 pin connections. Pins 1-4 are digital switches 
corresponding to the four modules 20a-20d, respectively. The voltage 
present at each pin is biased high (+5 VDC), enabling the corresponding 
module; when any of pins 1-4 is connected to ground, the corresponding 
module is disabled. Pin 9 is a +5 VDC power source and pin 10 is connected 
to ground. 
The selectors 60a-60d are connected at their common to ground pin 10 of 
jumper block 70. The OFF position of each selector 60a-60d is connected to 
the corresponding pin 1-4 of jumper block 70. When the switch 66 is in the 
OFF position, the connected pin 1-4 of jumper block 70 is grounded, 
disabling the corresponding module 20a-20d. When the switch 66 is in the 
ON position, current is allowed to flow through the resistor 64, 
activating LED 62 to indicate that the corresponding module 20a-20d is 
enabled, as the corresponding pin 1-4 of jumper block 70 is not grounded, 
and therefore remains biased high. 
A voltmeter 40 may be connected between negative terminal 24d and the 
cathode of diode 28 to measure the total DC voltage supplied by the power 
modules. Power may be supplied to the voltmeter 40 at pins 1 and 7 of the 
voltmeter 40 from pins 9 and 10 of the jumper block 70. 
The output from the power modules at positive terminal 22a is connected to 
a noise filter 50 at filter positive terminal 52 through output line diode 
28. The output line diode 28 is oriented with the cathode connected to the 
filter positive terminal 52, in order to provide reverse voltage 
protection to the combined power modules 20a-20d. The filter 50 is 
connected to a ground 110, such as a chassis ground. The filter positive 
output 56 is connected to the pulser positive terminal 92. The pulser 
negative terminal 94 and filter negative terminal 57 are connected to 
ground 110. 
Components which are acceptable for use with the circuit described above 
include VICOR model M48N 4.2 AF modules for power modules 20a-20d, a 
standard 4-stage 25 K.OMEGA. ganged potentiometer for potentiometer 32, 
TEXMATE model DVM-5 voltmeter for voltmeter 40 and a CORCOM 10KV3 filter 
for noise filter 50. Control jumper block 70 can be a standard VICOR 
modular switcher power supply main frame interface connector. Current 
limiting resistors 64 may have a value of 330 ohms. 
A variable power source 10 powered only by a 110 VAC source 120 using these 
components can provide from 28-200 VDC by enabling and disabling the power 
modules 20a-20d, and varying potentiometer 32, each of which individually 
can provide between 24 and 48 VDC. 
The power source 10 according to the invention using the items above is 
compact (approximately 13".times.13".times.7.5") and lightweight (less 
than 30 lbs.). 
Using the power modules 20a-20d with the switching and diodes 26a-26d, 28, 
a reliable, portable and easy to use variable DC power source 10 is 
obtained which can be used with known pulsers 90 to drive an 
electromagnetic acoustic transducer electromagnet 100 during field 
inspections. 
While a specific embodiment of the invention has been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.