current instruments can be purchased in a large variety of configurations.
Both analog and digital instruments are available. Instruments
are commonly classified by the type of display used to present
the data. The common display types are analog meter, digital readout,
impedance plane and time versus signal amplitude. Some instruments
are capable of presenting data in several display formats.
The most basic eddy current testing instrument consists of an
alternating current source, a coil of wire connected to this source,
and a voltmeter to measure the voltage change across the coil.
An ammeter could also be used to measure the current change in
the circuit instead of using the voltmeter.
While it might actually be possible to detect some
types of defects with this type of equipment, most eddy current
instruments are a bit more sophisticated. In the following pages,
a few of the more important aspects of eddy current instrumentation
will be discussed.