Scope Multimeter General Reference
109
9.11.5 Glossary of Common Terms
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 %.
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.
Pulse
A signal with abrupt (fast) signal direction changes in a positive
or negative direction, with consistent level and duration.
Pulse Period One complete on and off cycle or time period.
Pulse Train Collection of signal pulses traveling together.
Pulse Width (duration)
Measurement of a signals on time in a circuit that pulses on and
off. Specified in units of time.
Pulse Width Modulation
(PWM)
A signal that continuously cycles on and off while the on-time
varies within each cycle.
RMS
The RMS (root mean square) value of alternating currents and
voltages is the effective current or voltage applied, rather than
the peak current or voltage measurable. The AC RMS voltage
value can be defined as the equivalent DC voltage of the AC
voltage measured. RMS values are commonly used in AC
electrical measurement, as they are more representative of DC
measurements.
Sample Rate
Number of times (frequency) the scope/meter takes a sample of
the signal. Specified in mega samples per second (MS/s).
Sampling
Process of obtaining a sequence of instantaneous values for a
signal at regular or intermittent intervals. When a quantity of
samples are collected the operational status of the device is
determined.
Term / Abbreviation Description
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