Glossary of Terms

A

A-Scan

A single waveform of data as displayed on a Digital Oscilloscope.

A/D

Analog to Digital. Refers to the process of sampling analog data and converting it into digital format, e.g. when an A/D board (Digtizer) converts an analog waveform into digital information.

Amplitude

The height of data displayed on a Waveform. See Peak Amplitude.

APA

Absolute Peak Amplitude

B

B-Scan

an image consisting of a set of waveform data (A-Scans).

Beam

The waveform resulting from the use of one or more Elements in a Phased Array transducer.

BeamSet

One or more beams collected into a single acquisition.

Board

used as shorthand to describe a single A/D board in a computer system. Any board can have one or more Channels.

C

C-Scan

an image consisting of a feature collected from a Gate defined over a set of Waveform data (B-Scans).

Channel

a receiver of input data for an A/D board. A single A/D may have more than one input, but only a single channel: e.g. an AL8250 has an A and B input, but only one can be used at a time.

Cluster

a defect on a peak amplitude image that has been highlighted during Cluster Analysis.

Collection

The set of all feature data acquired during a single scan. A collection may contain other collections (e.g. Patch Scans or B-Scans).

D

dB

Decibels. A logarithmic quantity used to measure relative amplitude between one peak amplitude and another.

Digitizer

a device that converts analog information into digital information. See A/D.

F

Feature

A particular type of information collected from a gate. Peak Amplitude, Time of Flight, and Frequency Ranges are all examples of features.

FE

Falling Edge

FFT

Fast Fourier Transform

%FSH

Full Screen Height percentage. Refers to the magnitude of the ultrasonic signal as seen on the Digital Oscilloscope. 100% = top of the scope, -100% = bottom of the scope. 0 is the baseline.

G

Gate

A region in time from which waveform data and/or features are extracted. At minimum, a gate has a start time and an end time. Most gates have one or more associated thresholds. Gates are represented on the Digital Oscilloscope as lines, boxes, or highlighted regions. See Gates and Regions.

H

HPF

High Pass Filter. Frequencies higher than a specified value are passed and lower frequencies are attenuated.

Hz

Hertz. Unit of frequency: 1 Hz = 1 cycle per second.

L

Limit

A position along an axis at which motion is stopped. Hardware limits talk directly to the motor controller and prevent any further motion. Software limits allow the user to restrict the range of motion programmatically.

LPF

Low Pass Filter. Frequencies lower than a specified value are passed and higher frequencies are attenuated.

M

Main Bang

A term that refers to the initial burst of sound generated by the transducer. Usually visible on the Digital Oscilloscope as a large signal starting at the beginning of the generated waveform. This is usually marked as time zero.

MHz

Megahertz (1 MHz = 1 millon Hz)

N

NPA

Negative Peak Amplitude

O

ODIS

OKOS Dgitial Imaging System

P

PCM

Polarity Comparison Method

Peak Amplitude

The highest part of a waveform or waveform region. Usually measured in Volts or %FSH.

P/E

See Pulse/Echo.

P/C

See Pitch-Catch.

Pitch-Catch

Refers to the technique of using one transducer to send a signal, and another to receive the signal, when both transducers are on the same side of a part or are on two different sides of a part (but not directly opposite from each other).

PPA

Positive Peak Amplitude

P/R

Pulser/Receiver (See Pulser/Receiver Settings)

Pulse-Echo

Refers to the technique of using the same transducer to send and receive the ultrasonic signal.

PVDF

Refers to an ultrasonic transducer made from Polyvinylidene diflouride.

R

RE

Rising Edge

RTG

Relative Threshold Gates

S

SALI

Scanning Acoustic Layered Imaging

SAM

Scanning Acoustic Microscope

Sampling Rate

the frequency at which data is digitized. Measured in Hertz (Hz)

Scan

the act of acquiring a collection.

Scan Axis

the primary motor axis on which scanning is performed. In an XY raster scan, this is usually the "X" axis.

Step Axis

the secondary motor axis on which scanning is performed. In an XY raster scan, this is usually the "Y" axis.

T

TGC

Time Gain Correction. This refers to the technique of dynamically changing the gain of a signal while collecting.

Thickness

the difference between two signals in physical units (such as mm or inches). Often measured from a Front-Surface Follower. Material velocities can be used to calculate a thickness from a Time of Flight measurement.

Threshold

A level (in Volts or %FSH) that indicates how large an amplitude must be present for a feature to be collected. Signals that do not cross a given threshold are ignored.

Through Transmission

Refers to the technique of using one ultrasonic transducer to send the signal, and a second one to retrieve it, where the two transducers are on opposite sides of a part.

Time of Flight

The amount of time it takes to traverse from the Main Bang to the desired signal. May also refer to the difference in TOF between two signals (such as between a Front-Surface follower and a Data gate, see Thickness).

TOF

See Time of Flight.

Tranducer

a device that generates sound waves when a current is applied to it. Conversely, it generates a current when struck buy returning sound waves.

TT

See Through Transmission.

U

us

microseconds (1 microsecond = 1 millionth of a second)

V

V

Voltage or Volts (1 Volt = 1000 millivolts)

W

Waveform

data that shows changes in a recorded signal's amplitude over time.