Scope / Multimeter
General Reference
43
3.13.5 Glossary of Common Terms
70
63.0
42.0
31.5
80
72.0
48.0
36.0
90
81.0
54.0
40.5
100
90.0
60.0
45.0
Term / Abbreviation
Description
AC
Alternating Current - electrical current that switches
polarity at regular intervals.
Aliasing
An effect that causes an incorrect signal to be
displayed and/or causes a trigger to malfunction, due
to the input signal exceeding the sample rate of the
scope.
Amperage
The strength of an electric current, expressed in
amperes
Amplitude
Vertical magnitude (level or position) of a signal, or
the varying quantity from its zero value.
Buffer
An electronic reservoir for temporary storage of data
Cursor
Onscreen markers used to measure time, amplitude
and frequency
Coupling AC
Function used to subtract the average value of a
signal so that small variations can be displayed in the
waveform.
DC
Direct Current - electrical current that flows in one
direction only
Delta
Difference in time between two events.
Dropout
An intermittent or unwanted, vertical fall in a signal to
zero that may cause an undesired result.
Duty cycle
Measurement of the length of a signals on time.
Specified as a percentage (ratio), of the total cycle
time.
Dwell
Used to measure a signals on time in degrees of
dwell. Commonly used to measure mixture control
solenoids on carbureted feedback engines and
specified in duty cycle %.
Duty % to Dwell Conversions
Duty Cycle
Dwell
%
4 cyl
6 cyl
8 cyl
Dwell 60
Measurement of the length of a signals on time
displayed on a 0 to 60 degree scale. 0° = 0%; 30° =
50%; 60° = 100%.
Dwell 90
Measurement of the length of a signals on time
displayed on a 0 to 90 degree scale. 0° = 0%; 45° =
50%; 90° = 100%.
Filter
Function used to filter or smooth out spikes and fast
variations in signals.
Frequency
The number of times a signal repeats in one second.
Measured in Hertz (cycles per second).
Glitch
An intermittent or unwanted, error in a signal that may
cause a false or undesired result.
Grid
The graph displayed on the scope screen that is
made up of the x and y axis scales that aid in the
measuring of signal characteristics.
Horizontal Scale
See Sweep Scale
Invert
Function used to switch signal polarity,
Lambda (l)
Used to represent a numerical value denoting the
actual measured air/fuel ratio with respect to the ideal
air/fuel ratio at stoichiometry. Lambda equals one (1)
when the actual air/fuel ratio is equal to the theoretical
(stoichiometric) air/fuel ratio of 14.7 (14.66) to 1.
Lambda less than 1 means excess fuel; greater than
1 means excess air.
Megasamples per second (MS/
s)
Sample rate unit equal to one million samples per
second
Noise or Hash
Unwanted voltage, current or signal interference that
is imposed on a signal.
Parasitic Voltage
Trace voltage in a circuit after the main power source
is disconnected.
Peak
The maximum amplitude value present in a varying or
alternating voltage. This value may be either positive
or negative.
Peak Detect
Peak detect captures and evaluates all signal sample
points, in order to display fast occurring events or
glitches.
Pressure Transducer
Electronic device that converts pressures (negative/
positive) to electrical signals.
Term / Abbreviation
Description
