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) displayed as 2D image.

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

a 2D 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; or it may have multiple independent inputs.

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.

DPR

Digital Pulser/Receiver. a P/R that can be controlled directly from the software.

E

Element

a single transducer in a Phased Array Probe.

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. A process that converts a Time-based waveform, i.e. time on the horizontal axis and voltage on the vertical axis, into a Frequency-based waveform, i.e. frequency on the horizontal axis, and Vrms on the vertical axis. This is used to find the frequency components of a signal.

%FSH

Full Screen Height percentage. Refers to the magnitude of the ultrasonic signal as seen on the Digital Oscilloscope. for an RF signal, 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.

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 communicate 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.

Material Velocity

the speed of sound within a specific material. Different materials have different Material Velocities.

MHz

Megahertz (1 MHz = 1 millon Hz)

N

NPA

Negative Peak Amplitude

O

ODIS

OKOS Dgitial Imaging System

P

PCM

Polarity Comparison Method. An alternate method of detecting Phase Inversion. See Phase Inversion Detection.

Peak Amplitude

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

P/E

See Pulse/Echo.

P/C

See Pitch-Catch.

Phased Array Probe

A device that consists of a series of transducer Elements arranged in a sequence. Elements can be in a linear array, a grid, or a curved shape. Elements can be combined into Virtual Probes that behave like a single transducer.

Phase Inversion

refers to the phenomenon when the waveform cycle reverses, e.g. instead a signal showing a positive-going lobe before a negative going lobe (like a sine wave), it shows a negative before a positive. The presence of phase inversion can indicate a change in material has occurred.

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 Digital Pulser/Receivers)

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. Refers to a signal that is crossing a gate threshold from a low amplitude to a higher amplitude.

Region

Usually refers to a selected period of time that acts as a gate with no threshold. For example, B-Scan and FFT regions.

Rep Rate

short for Repetition Rate. This can refer to several events:

• The rate at which the Pulser/Receiver is running in hertz
• The rate at which the A/D is triggering
• On an Olympus FocusPX, the rate at which data collection is running internally

RP

Remote Pulser. A module attached to a DPR500 or DPR650 that generates the pulse sent to the transducer. See Digital Pulser/Receivers.

RTG

Relative Threshold Gate. Used for detecting Phase Inversion of a signal. The gate contains thresholds that are set to a percentage of the absolute Peak Amplitude detected in the gate region, and thus are relative rather than absolute. See Phase Inversion Detection.

S

SALI

Scanning Acoustic Layered Imaging. SALI Gates are used to collect data on many material layers at once. See Gates.

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.

Scan Envelope

the area in which the ultrasonic transducer(s) can be moved. It should be possible to orient the transducer so that it is in any part of the scan envelope.

T

TGC

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

THAP

Thickness to Absolute Peak, e.g. the Maximum of the absolute values of the Positive Peak and the Negative Peak

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.

THNP

Thickness to Negative Peak Amplitude

THPP

Thickness to Positive Peak Amplitude

Threshold

A level (in Volts or %FSH) that indicates how large an amplitude must be 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.

TOFAP

TOF to Absolute Peak Amplitude, e.g. the Maximum of the absolute values of the Positive Peak Amplitude and the Negative Peak Amplitude

TOFNP

TOF to Negative Peak Amplitude

TOFPP

TOF to Positive Peak Amplitude

Tranducer

a device that generates sound waves when a current is applied to it. Conversely, it generates a current when struck by returning sound waves. Multiple transducers can be combined into a Phased Array Probe.

TT

See Through Transmission.

U

us

microseconds (1 microsecond = 1 millionth of a second)

V

V

Voltage or Volts (1 Volt = 1000 millivolts)

Virtual Probe

in Phased Array acquisition, this refers to the collection of elements used to create a single waveform result.

W

Waveform

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