Oscilloscope Glossary

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

Alternate Mode – A display mode of operation in which the oscilloscope completes tracing one channel before beginning to trace another channel.

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 create a glowing trace wherever the beam hits.

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.

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

CAN - Controller Area Network, a serial communication standard popular in automotive and industrial applications.

Chop Mode – A display mode of operation in which small time segments of each channel are traced sequentially so that more than one waveform can appear on the screen simultaneously.

Circuit Loading – 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.

Delayed Time Base – A time base with a sweep that can start (or be triggered to start) relative to a pre-determined 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 Oscilloscope – A type of oscilloscope that uses an analog–to–digital converter (ADC) to convert the measured voltage into digital information. Three types: digital storage, digital phosphor, and digital sampling oscilloscopes.

Digital Phosphor Oscilloscope (DPO) – A type of digital oscilloscope that models the display characteristics of an analog oscilloscope while providing digital oscilloscope benefits such as waveform storage. The DPO oscilloscope provides intensity-graded viewing of signal characteristics in real time, and 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 Storage Oscilloscope (DSO) – A digital oscilloscope that acquires signals with digital sampling using an analog-to-digital converter (ADC). It uses a serial-processing architecture to control acquisition, user interface, and the raster display.

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.

Frequency – The frequency equals 1/period.

Frequency Response – A Bode plot of input to output response of an amplifier or attenuator for sine waves with constant amplitudes at different frequencies over a frequency range.

Gain Accuracy - An indication of how accurately the vertical system attenuates or amplifies a signal, usually represented as a percentage error.

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

Graticule - The grid lines on a screen for measuring oscilloscope traces.

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

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.

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

Mixed-Signal Oscilloscope (MSO) - Digital oscilloscopes that have a larger number of channels for viewing both analog and digital signals together. MSO scopes typically have two tor four analog channels and at least 8 bits of vertical resolution. There are usually 16 digital channels but they typically have only 1 bit of vertical resolution.

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 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.

Ramp – Transition between voltage levels of sine waves that change at a constant rate.

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%.

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 equivalenttime 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).

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 screen, 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.

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

Sweep Speed – Same as the time base.

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

Trace – The shapes drawn on an analog oscilloscope cathode-ray tube (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.

Vertical Resolution – how precisely an analog-to-digital converter (ADC) in a digital oscilloscope converts input voltages into digital values, measured in bits.

Vertical Sensitivity – how much the vertical amplifier in an oscilloscope can amplify a weak signal, measured in millivolts (mV) per division.

Wave – a signal that repeats regularly over time. Common types include: sine, square, rectangular, saw-tooth, triangle, step, pulse, periodic, non-periodic, synchronous, asynchronous.

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

Waveform Capture Rate – 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.

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