Glossary of Terms

A

Acquisition Mode – Modes that control how waveform points are produced from sample points. Some types include sample, peak detect, hi res, envelope, average, and waveform data base.

Alternating Current (AC) – A signal in which the current and voltage vary in a repeating pattern over time. Also used to indicate signal coupling type.

Amplification – An increase in signal amplitude during its transmission from one point to another.

Amplitude – The magnitude of a quantity or strength of a signal. In electronics, amplitude usually refers to either voltage or power.

Analog-to-Digital Converter (ADC) – A digital electronic component that converts an electrical signal into discrete binary values.

Analog Oscilloscope – An instrument that creates a waveform display by applying the input signal (conditioned and amplified) to the vertical axis of an electron beam moving across a cathode-ray tube (CRT) screen horizontally from left to right. A chemical phosphor coated on the CRT creates a glowing trace wherever the beam hits.

Analog Signal – A signal with continuously variable voltages.

Attenuation – A decrease in signal amplitude during its transmission from one point to another. Averaging – A processing technique used by digital oscilloscopes to reduce noise in a displayed signal.

B

Bandwidth – A frequency range, usually limited by –3 dB.

C Circuit Loading – The unintentional interaction of the probe and oscilloscope with the circuit being tested, distorting the signal.

Compensation – A probe adjustment for passive attenuation probes that balances the capacitance of the probe with the capacitance of the oscilloscope.

Coupling – The method of connecting two circuits together. Circuits connected with a wire are directly coupled (DC); circuits connected through a capacitor or transformer are indirectly (AC) coupled.

Cursor – An on–screen marker that you can align with a waveform to make more accurate measurements.

D

Delayed Time Base – A time base with a sweep that can start (or be triggered to start) relative to a predetermined time on the main time base sweep. Allows you to see events more clearly and to see events that are not visible solely with the main time base sweep.

Digital Signal – A signal whose voltage samples are represented by discrete binary numbers. Digital Oscilloscope – A type of oscilloscope that uses an analog-to-digital converter (ADC) to convert the measured voltage into digital information. Types include: digital storage, digital phosphor, mixed signal, and digital sampling oscilloscopes.

Digital Phosphor Oscilloscope (DPO) – A type of digital oscilloscope that closely models the display characteristics of an analog oscilloscope while providing traditional digital oscilloscope benefits (waveform storage, automated measurements, etc.) The DPO uses a parallel-processing architecture to pass the signal to the raster-type display, which provides intensity-graded viewing of signal characteristics in real time. The DPO displays signals in three dimensions: amplitude, time and the distribution of amplitude over time.

Digital Sampling Oscilloscope – A type of digital oscilloscope that employs equivalent-time sampling method to capture and display samples of a signal, ideal for accurately capturing signals whose frequency components are much higher than the oscilloscope’s sample rate.

Digital Signal Processing – The application of algorithms to improve the accuracy of measured signals.

Digital Storage Oscilloscope (DSO) – A digital oscilloscope that acquires signals via digital sampling (using an analog-to-digital converter). It uses a serial processing architecture to control acquisition, user interface, and the raster display.

Digitize – The process by which an analog-to-digital converter (ADC) in the horizontal system samples a signal at discrete points in time and converts the signal’s voltage at these points into digital values called sample points.

Direct Current (DC) – A signal with a constant voltage and/or current. Also used to indicate signal coupling type.

Division – Measurement markings on the oscilloscope graticule indicating major and minor marks.

E

Earth Ground – A conductor that will connect electrical currents to the Earth.

Effective Bits – A measure of a digital oscilloscope's ability to accurately reconstruct a sine wave signal’s shape. This measurement compares the oscilloscope's actual error to that of a theoretical “ideal” digitizer.

Envelope – The outline of a signal’s highest and lowest points acquired over many displayed waveform repetitions.

Equivalent-time Sampling – A sampling mode in which the oscilloscope constructs a picture of a repetitive signal by capturing a little bit of information from each repetition. Two types of equivalent-time sampling: random and sequential.

F

Focus – The analog oscilloscope control that adjusts the cathode-ray tube (CRT) electron beam to control the sharpness of the display.

Frequency – The number of times a signal repeats in one second, measured in Hertz (cycles per second). The frequency equals 1/period.

Frequency Response – Frequency response curves of an oscilloscope define the accuracy in amplitude representation of the input signal in function of the signals frequency. In order to obtain maximum signal fidelity, it is important that the oscilloscope has a flat (stable) frequency response across the entire specified oscilloscopes bandwidth.

G

Gain Accuracy – An indication of how accurately the vertical system attenuates or amplifies a signal, usually represented as a percentage error. Gigahertz (GHz) – 1,000,000,000 Hertz; a unit of frequency.

Glitch – An intermittent, high-speed error in a circuit.

Graticule – The grid lines on a display for measuring oscilloscope traces.

Ground – 1. A conducting connection by which an electric circuit or equipment is connected to the earth to establish and maintain a reference voltage level. 2. The voltage reference point in a circuit.

H

Hertz (Hz) – One cycle per second; the unit of frequency.

Horizontal Accuracy (Time Base) – An indication of how accurately the horizontal system displays the timing of a signal, usually represented as a percentage error.

Horizontal Sweep – The action of the horizontal system that causes a waveform to be drawn.

I

Intensity Grading – Frequency-of-occurrence information that is essential to understanding what the waveform is really doing.

Interpolation – A “connect-the-dots” processing technique to estimate what a fast waveform looks like based on only a few sampled points. Two types: linear and sin x/x. K Kilohertz (kHz) – 1,000 Hertz; a unit of frequency.

L

Loading – The unintentional interaction of the probe and oscilloscope with the circuit being tested which distorts a signal.

Logic Analyzer – An instrument used to make the logic states of many digital signals visible over time. It analyzes the digital data and can represent the data as real-time software execution, data flow values, state sequences, etc.

M

Megahertz (MHz) – 1,000,000 Hertz; a unit of frequency.

Megasamples per second (MS/s) – A sample rate unit equal to one million samples per second.

Microsecond (μs) – A unit of time equivalent to 0.000001 seconds.

Millisecond (ms) – A unit of time equivalent to 0.001 seconds.

Mixed Domain Oscilloscope(MDO) – A type of digital oscilloscope that combines an RF spectrum analyzer with a MSO or DPO to enable correlated views of signals from the digital, analog, to RF domains.

Mixed Signal Oscilloscope (MSO) – A type of digital oscilloscope that combines the basic functionality of a 16-channel logic analyzer with the trusted performance of a 4-channel digital phosphor oscilloscope.

N

Nanosecond (ns) – A unit of time equivalent to 0.000000001 seconds.

Noise – An unwanted voltage or current in an electrical circuit.

O

Oscilloscope – An instrument used to make voltage changes visible over time. The word oscilloscope comes from “oscillate,” since oscilloscopes are often used to measure oscillating voltages.

P

Peak (Vp) – The maximum voltage level measured from a zero reference point.

Peak Detection – An acquisition mode available with digital oscilloscopes that enables you to observe signal details that may otherwise be missed, particularly useful for seeing narrow pulses spaced far apart in time.

Peak-to-peak (Vp-p) – The voltage measured from the maximum point of a signal to its minimum point.

Period – The amount of time it takes a wave to complete one cycle. The period equals 1/frequency.

Phase – The amount of time that passes from the beginning of a cycle to the beginning of the next cycle, measured in degrees.

Phase Shift – The difference in timing between two otherwise similar signals.

Pre-trigger Viewing – The ability of a digital oscilloscope to capture what a signal did before a trigger event. Determines the length of viewable signal both preceding and following a trigger point.

Probe – An oscilloscope input device, usually having a pointed metal tip for making electrical contact with a circuit element, a lead to connect to the circuit’s ground reference, and a flexible cable for transmitting the signal and ground to the oscilloscope.

Pulse – A common waveform shape that has a fast rising edge, a width, and a fast falling edge.

Pulse Train – A collection of pulses traveling together.

Pulse Width – The amount of time the pulse takes to go from low to high and back to low again, conventionally measured at 50% of full voltage.

R

Ramps – Transitions between voltage levels of sine waves that change at a constant rate.

Raster – A type of display.

Real-time Sampling – A sampling mode in which the oscilloscope collects as many samples as possible from one triggered acquisition. Ideal for signals whose frequency range is less than half the oscilloscope’s maximum sample rate.

Record Length – The number of waveform points used to create a record of a signal.

Rise Time – The time taken for the leading edge of a pulse to rise from its low to its high values, typically measured from 10% to 90%.

S

Sampling – The conversion of a portion of an input signal into a number of discrete electrical values for the purpose of storage, processing and/or display by an oscilloscope. Two types: real-time sampling and equivalent-time sampling.

Sample Point – The raw data from an ADC used to calculate waveform points.

Sample Rate – Refers to how frequently a digital oscilloscope takes a sample of the signal, specified in samples per second (S/s).

Sensor – A device that converts a specific physical quantity such as sound, pressure, strain, or light intensity into an electrical signal.

Signal Integrity – The accurate reconstruction of a signal, determined by the systems and performance considerations of an oscilloscope, in addition to the probe used to acquire the signal.

Signal Source – A test device used to inject a signal into a circuit input; the circuit’s output is then read by an oscilloscope. Also known as a signal generator.

Sine Wave – A common curved wave shape that is mathematically defined.

Single Shot – A signal measured by an oscilloscope that only occurs once (also called a transient event).

Single Sweep – A trigger mode to display one triggered screen of a signal and then stop.

Slope – On a graph or an oscilloscope display, the ratio of a vertical distance to a horizontal distance. A positive slope increases from left to right, while a negative slope decreases from left to right.

Square Wave – A common wave shape consisting of repeating square pulses.

Sweep – One horizontal pass of an analog oscilloscope’s electron beam from left to right across the CRT screen.

Sweep Speed – Same as the time base.

T

Time Base – Oscilloscope circuitry that controls the timing of the sweep. The time base is set by the seconds/division control.

Trace – The visible shapes drawn on a CRT by the movement of the electron beam.

Transient – A signal measured by an oscilloscope that only occurs once (also called a single–shot event).

Trigger – The circuit that references a horizontal sweep on an oscilloscope.

Trigger Holdoff – A control that allows you to adjust the period of time after a valid trigger during which the oscilloscope cannot trigger.

Trigger Level – The voltage level that a trigger source signal must reach before the trigger circuit initiates a sweep.

Trigger Mode – A mode that determines whether or not the oscilloscope draws a waveform if it does not detect a trigger. Common trigger modes include normal and auto.

Trigger Slope – The slope that a trigger source signal must reach before the trigger circuit initiates a sweep.

V

Vertical Resolution (Analog-to-Digital Converter) – An indication of how precisely an analog-to-digital converter (ADC) in a digital oscilloscope can convert input voltages into digital values, measured in bits. Calculation techniques, such as hi res acquisition mode, can improve the effective resolution.

Vertical Sensitivity – An indication of how much the vertical amplifier can amplify a weak signal – usually measured in millivolts (mV) per division.

Volt – The unit of electric potential difference.

Voltage – The difference in electric potential, expressed in volts, between two points.

W

Wave – The generic term for a pattern that repeats over time. Common types include: sine, square, rectangular, sawtooth, triangle, step, pulse, periodic, non-periodic, synchronous, asynchronous.

Waveform – A graphic representation of a voltage varying over time.

Waveform Capture Rate – Refers to how quickly an oscilloscope acquires waveforms, expressed as waveforms per second (wfms/s).

Waveform Point – A digital value that represents the voltage of a signal at a specific point in time. Waveform points are calculated from sample points and stored in memory.

Writing Speed – The ability of an analog oscilloscope to provide a visible trace of the movement of a signal from one point to another. This ability is restrictive for low-repetition signals that have fast-moving details, such as digital logic signals.

X

XY Mode – A measurement technique that involves inputting one signal into the vertical system, as usual, and one into the horizontal system to trace voltages on both the X and Y axis.

Z

Z Axis – The display attribute on an oscilloscope that shows brightness variations as the trace is formed.