Lecroy LTXXX-OM-E-Rev-B Operating

G LOSSARY OF T ECHNICAL T ERMS

Acquisitio nT ime: In a sample-and-hold or track-a nd-hold circuit, the time re quired after the sample or track

command f or theoutput to slewthrough a full-scale voltage changeand settleto its final valuewithin a
specified error band.

ACSN: auto-correlation signal-to-noise
ADC: ana lo g -to-digital converter.
Aliasing: Whe never a dy n a m ic signa l is synchrono u slysamp le d , a possibility of misunde rstanding its frequency

content exists. This difficulty is termed “aliasing” and occurs whenever the sampling rate is less than twice the
highest frequency component in the signal being measure d.

AND: Logica l de signation or circuit fu n ction meanin gtha t all inputs must be in the TRUE state for a TRUE
output.

ApertureJitter : In a sample-hold or ADC, the jitter betw e en the time of the sample (or convert) command
pu lseand the timeth einput signal is actually sampled. This jitter is usually due to thermal noise . It lea d s to an
uncertaintyinthesampledamplitude equal to deltat*dV/dt, wheredeltat istheaperturejitter, and dV/dt is
therateof changeof theinputvoltageatthetimeof sampling.Theterms“aperturejitter” and“aperture
uncertainty” are often used interchangeably .

ApertureUncertainty : In a sample-hold or ADC, the total uncertainty in the time of the sample (or convert)
command pulseand thetime theinput signal is actually sampled, dueto all causes inclu din gnoise , signa l
amplitude -dependent delayvariation (as in a flash ADC), tempe rature, etc. Often used interchange ably with
“aperture jitter,” but “ aperture uncertainty” is the more inclusive term.

Area: In a time domain DSO waveform measurement, area is the sum of the sampled values between the
cursors times the duration of a samp le.

Artifact Rejection: Used in summed averaging to exclude waveforms that have exceeded the dynamic range of
the recording system.

Autom atic Setup: In an oscillosco p e, au toma tic scaling of thetim e base, trigger, andsensitivity setting s .
Providesa stabledisplay of repetitiveinput signals.

Ave rage: See Me an Value, Summed Averaging and Continuou s Averaging.
AWG: arbitrary wave generator
Bandwidth: In normal use, thefrequency rangeover which the gain of an amplifier or other circuit does not

vary by more than 3 dB.

BE R:SeeBitErrorRate.
Binning: A technique for combining points in a histogram to be compa tible with the resolution of the display

device.
Bit: An abbre viation of “binary digit,” one of the tw o numbers, 0 and 1, used to encode data. A bit is often

expressed by a high or low electrical voltage .

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Bit ErrorR ate: Ratio of the number of bits of a message incorrectly received to the total number received.
CCD: Charge Coup led Device. An integrated circuit that allows the transfer of a variable amount of charge

through a series of cells; an analog shift register.

CCTM: clock certification test module
Channel: A path through an arrangement of components (modules and electrical or optical cabling or both)

alon gwhic h signals can be sent.
Clamping: Holding a circuit point to some reference level (frequ ently ground) by means of a low-impedance

element such as a saturated transistor, FET, forward-biased diode, relay , etc.
Coherent Gain: The normalized coherent gain of a filter corre sponding to each window function is 1.0 (0 dB)

for the rectangu lar windowand less than 1.0 for other windows. It defines the loss of signal energy due to the
multiplication by the window function.

CommonModeRange: Themaxim u mra n g e(usually voltage ) w ithin wh ichdifferen tial inpu ts can ope rate
w ithout a loss of accuracy.

CommonModeRejectionRatio: The ratio of the common-mode inpu t voltage to the output voltage
expressed in dB. The extent to which a differential amplifier does not provide an output voltagewhen the same
signalisappliedtobothinputs.

CommonModeSignal (Noise): The signal (usually noise) that appears equally and in phase on each of the
differential signal conductors to ground. Se e Differe ntial Input.

Contin uo us Av eragin g: Sometimes called “exponential averaging,” the technique consists of the rep eated
addition, with unequal we ight, of successive source w ave forms. Each newwa veform is added to the
accu m u late dave rag eaccordin gto the formula : S(i,n ew)= N/(N+ 1) * [S(i,old)+ 1/ (N+1) * W(i) ] w h erei =
index over all data points of the wave forms; W(i) = newly acquire d waveform;S(i,old) = old accumulated
ave rage ; S(i,new )= newaccumula ted ave rage ; N = weig hting factor (1,3,7...).

ConversionCycle: E ntire seque nce involve d in changing data from one form to another, e .g.,digitizing an
analog quantity , changing binary data to BCD, etc.

Crosstalk : Unw a nted coupling of a signal from one channel to another.
Cursor: A visible marke r that identifies a horizon tal or ve rtical p os ition, or both, on anoscilloscopedisplay .

LeCroy DSOs offer “waveform riding” cursors that convenientlygive both the horizonta l and vertical values
w ithout selecting one or theothe r.

DAC: digital-to-analog converter
Data Logger: An instrument that accep ts input signals (usually slowanalog), digitizes them, and stores the

results in me moryfor later readout. The digital equ ivalent of a strip-chart recorder.

DC: Direct curre n t. Normally mea n s a voltageor current that re mains con stant.
DC Level Shift: A change in the nominal DC voltage level present in a circuit.
DC Offset: SeeDC L evel Shift. This term may imply that the shift is intentional, for example, adjustable by a

control knob.

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Technical Terms

DC Overload: An overload signal of long duration compared to the normal input pulse width or duty ratio of

a circuit.
DeadTime: Ina dig ital oscilloscope, thedea dtimeis the tim efrom th eend of oneacqu isition of data to the
start of thenext acquisition.

Decimation: The process of reconstructing a source w ave form with a reduce d number of data points by using
only every nth data point, where n is an integ er.

Differ en tial Input: A circu it with two inputs tha t is sensitiveto th ealge bra ic diffe ren cebetw een the two .
Differ en tial L inear ity:Atermofteninappropriatelyusedtomeandifferentialnon-linearity.
Differ en tial N on-Linear ity:1. Thepercentagedeparturefromtheaverageof theslopeof theplot of output

versus input fromthe slopeof a referenceline; 2. The percentage of variation in ADCs or TDCs from the
mean of theana log(or time )wid th of anysingle dig ital step . It is usually measu re dby driving the input with a
large number of random amplitude pulse s and then measuring the relative number of events in each digital bin.

Differ en tial Output: A circuit with two outputs supplying one normal and one complementary level of outp ut
signa l.

Differ en tial Pulses: Tw ooppos ite pola rity pulses coincid e n t in time.
Dithering: Typ ically used w h e nave rag in gsignals (which havelownoise content) to improv evertical resolution

and decre ase the effects of an ADC's non-linearities. The technique applies different offsets to each incoming
w ave form to ensure the signal is not always digitized by the same portion of the ADC. The offsets must be
subtracted from the recorded signals before being included in the summed average.

Digital Filterin g: The manipulation of digital data to both enhance desirable and to remove undesirable
aspects of the data.

Dropout Trigger: A trigger that occurs if the input signal drops out for a time period longer than a preset
amount (betwee n 25 ns to 20 s on some LeCroy DSOs). This is very useful for triggering on microprocessor
cra shes, network hangups, bus contention problems or other phenomena whe re a signal stops occurring .

DutyCycle: A comp u te d va lu ein dig ital scopes repres e n ting the ave rag eduration abo v emidpoint valueas a
percentage of theperiod for timedomainwaveforms.

DynamicRange: The ratio of the largest to smalle st signal that can be accura tely processed by a module.
DynamicRAM (DRAM): A ra ndom access memory in which the internal memory must be refreshed

periodica lly .
ECL: Emitter-coupled logic, an unsa tura tedlogic performed by emitter-coup led transistors. Usu a lly, ECL

LOGICAL 1 = −1.6VandLOGICAL0=−0.8 V.
EMI: Electromagnetic interference caused by current or voltage induced into a signal conductor by an

electromagnetic field.
EN BW (Equivalen t Noise Ban dwidth): For a filter associated with each frequency bin, EN BW is the

bandw idth of an equiva lent rectangular filter (having the same gain at the center frequency) that would collect
the same powe r from a white noise signal.

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E nhanced Resolution (ERE S): A fac ility in L eCro yDSOs to increa setheamp lituderesolution of sin g le-shot

wave form measureme n ts. This technique, w h ichapplies dig ital filteringto achieve resolution enh a n ce m e n t at a
reduced bandwidth, is optimum when the sampling rate of the instrument ex ceeds that required for the input
signal bandw idth. For repetitive signals, either E RES or Signal Averaging, or both, can be use d to achieve
high er resolution with substantiallysmaller loss of bandwidth than for single -shot signals .

Envelope: Themaximum, minimum, or maximum and minimu m values of a sequence of measured
w ave forms. In LeCroy DSOs, the number is programmable from 1 to 10

EPROM: E rasable, programmable read-only memory. An integrate d circuit memory array that is made with a
pattern of either all log ical zeros or ones and has a pattern written into it by the user with a special hardw are
program.

E quivalent Time Sampling (E QT): (Also known as E TS.) A means of exploiting multiple acquisitions of a
repetitivesignal to increasetheusable bandwidth of a digitizer bymakingit appear to samplemore rapidlythan
its maximum single-shot sample rate. Works only with stable, repetitive signals.

Extrema: The computation of a w a veform enve lope, by repe ated comparison of successive wa veforms, of all
maximum points (roof) and all minimum points (floor). Whene ver a given data point of the newwave form
excee ds the corresponding maximum value in the roof record, it is used to replace the previous value.
Whenever a given data point of the newwave form is smaller than the corresponding floor value, it is used to
replace the previous value.

Falltime: Unless othe rwise defined, the time re quired for a pulse to go from 90 % to 10 % of full amplitude.
Can also refe r gen e ra llyto the trailin gedgeof a pulse.

Fast Fourier Transform (FFT): In signal proce ssing applications, an FFT is a mathematical algorithm that
takes a discrete source w ave form, defined over n points, and compute s n comp lex Fourier coefficients, which
are interpreted as harmonic components of theinput signal. For a “real” source wave form (imaginarypart
equals 0), there are n/2 independent harmonic components.

Feedth r o ugh: An unwanted signal that passe s a closed gate or disabled input.
FFT:SeeFastFourierTransform.
FFT FrequencyBins: A Fast Fourier Transform (FFT) corresponds to analyzing the input signal with a bank

of n/ 2 filters, all having the same shape and width, and centered at n/2 discrete freque ncies. E ach filter collects
the signal energy that falls into the immediate neighborhood of its center fre que ncy , and thus it can be said that
there are n/2 “frequency bins.” The distance, in Hz, betwe en the center frequencies of two neighboring bins is
alw ay s: delta f = 1/T, where T is theduration of the time-domain re cords in seconds. The nomina l w idth of
binisequaltodeltaf.

6

.

FFT FrequencyRange: The rangeof frequencies computed and displa yed in an FFT is 0 Hz to the Nyquist
frequency.

FFT Frequen cyResolution : In a narrow sense, the frequency resolution is equal to the bin width, delta f.
That is, if the input signal changes its frequency by delta f, the corresponding spectrum peakwill be displaced
by delta f. For smaller changes of frequency, only the shape of the peak will change. How e ver, the effective
fre q u ency resolu tion (i.e., the ability tore so lv etwo signals wh o sefreq u e n cies arealmost thesame)is furthe r

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Technical Terms

limited by the use of window functions. The E NBW value of all window s other than the rectangular is grea ter
than delta f (i.e., greate r than the bin width).

FFT N umber of Points: FFT is compute d over the number of points (Transform Size) whose upper bound
is thesource number of points. FFT generates spectra having n/ 2 output points.

FFT TotalPower: Are a under thepowe r density spe ctrum in freque ncy-domain measurements.
FIFO: First-in, first-out shift re gisters (sometimes called first-in, first-out memory).
Filter: An electronic circuit or digital data manipulation routine that either enhances desirableor removes

undesirable aspects of an analog wave form or its digital rep resentation. Filters are used to block specific
frequencycomponents from passing through a circuit, to linea rize othe rwise ide ntical components (such as
CCDs) used in a common circuit, or to pe rform wa veform integration, differentiation, or smoothing, just to
name a few typ es.

Flash ADC: A very fast analog-to-digital conve rter, usually consisting of a large set of fast comparators and
associated logic, in which the analog signal simultaneously is compared to 2n − 1 different reference voltages,

w h e ren is theADC re so lu tion. Also called a parallel con verter.
Floor : The record of points that mak e the bottom (or minimum) of an enve lope created from a succession of

wavef orms.
FWH M: Full-Width Half Maximum. The width of a pulse or w ave form at 50 % amplitude used to measure

the duration of a signal.
Gate: 1. A circuit element used to provide a logical function (e.g ., AN D, OR); 2. An inpu t control signa l or

pulse enabling the passage of other signals.
Glitch: A sp ike or short-time duration structural aberration on an otherwise smooth w ave form that is normally

characterized by more gradual amplitudechanges. In digital electronics, where the circuit under te st uses an
internal clock, a glitch can be considered to be any pulse narrowe r than the clock w idth.

GlitchTr igger: A trigge r on pulsewidths smalle r tha na givenvalue.
Ground Loop: A long ground connection along which voltage drops occur due either to heavy circuit current

or external pick-up, with the result that circuit elements referred to different points along it operate at different
effective ground references.

HF Sync: Reduces the trigger rate by including a frequency divider in the trigger path, enabling the input
trigg er rate to exce ed themaxim u m for repetitive signals .

Histogram: A graphical representation of data such that thedata is divided into interva ls or bins. The intervals
or bins arethen plotted on a bar chart whe re the height is proportional to the number of data points contained
in each interval or bin.

Holdoff by Events: Selects a minimum number of events betw e en triggers. An event is generated whe n the
trigger source meets its trigger conditions. A trigger is generated whe n the trigger condition is met after the
selected number of events from the last trigger. The hold-off by events is initialized and started on each
trigger.

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Holdoff by Time: Selects a minimum time between triggers. A trigger is generated when the trigger condition

is met after the selected delay from the last trigger. T he timing for the delay is initialized and started on each
trigger.

HPGL: Hewlett-Packard Graphics LanguageFormat; Hewlett-PackardC ompany.
Hybr id Circuit: A small, self-contained, high-density circuit element usually consisting of screened or

deposite d conductors, insulating areas, resistors, etc., with welded or bonded combinations of discrete circuit
elements and integrated circuit chips.

IC: Integrated Circuit. A self-contained, multiple-element circuit such as a monolithic or hybrid.
Integr alL in earity:Atermoftenusedinappropriatelytomeanintegralnon-linearity.
Integral N on- L inearity: Deviation of ADC respo ns efrom an app ropria te straight linefit. The spe cification is

sometimes defined as maximum deviation, expressed as a fraction of full scale. More recent ADCs have a
spe c ification exp re ssed as a pe rce nt of readin gplus a constant.

In terleav ed Clo ckin g: Supplying clock pulses of equal frequency but diffe rent identical circuits or instruments
in order to increase the syste m samp le rate. For example , use of tw o transient recorders w ith inputs in paralle l
but complementa ry clocks to allow operation at tw ice the maximum ra te of a single unit.

Interval Trigger: Se lects an interval betwee n tw o edges of the sameslope . The trigger can be generated on the
second edge if it occurs within the selected interval or after the selected interval. The timing for the interval is
initializedand restarte dwhe n ever theselec ted edgeoccurs.

Jitter: Short-te rm fluctuations in the output of a circuit or instrument that are independent of the input.
Leakage: When observing the Power Spectrum of a sine w a ve having an integral number of periods in the

time windowusing the rectangular window, leakage is the broadening of the base of the peakspectral
component that accuratelyrepresentsthesourcewavefor m’s amplitude.

Limiter: A circuit ele ment th a t limits the amplitudeof an inpu t (use dfor input protec tion, pulsestandardizin g ,
etc.).

Logical 1: A signal level indicating the TRUE state; corresponds to the unit being set (i.e., if interrogated, the
answ er is yes).

Logical 0: A signal level indicating the FALSE state; corresponds to the unit N OT being set (i.e., if
interrogated, the answe r is no).

Lon g-TermStability: Re fers to stability over a long time, suc h as se veral da ys or mon ths.
MCA: multichannel analyzer (e.g ., pulse height analyzer)
MeanValue: Averag eor DC level of all da ta points selectedin a w aveform.
Median Value: The data value of a wave form above and below which there are an equal number of data

points.

Mode Value: The most freque ntly occurring data value of a w ave form.

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Technical Terms

MonolithicIC: An integrated circuit whose elements (transistors, diodes, resistors, small capacitors, etc.) are

formed on or within a se miconductor substrate .

Monotonic: A function with a derivative that does not change sign.
Multiplex er : A deviceused to selectively switch a number of signal paths to oneinput or outpu t.
NAN D: An AN D circuit, except with a complementary (negative true) output.
Negation: The proce ss of transposing all negative values into positives and all positive values into negatives.
NLTS: non-linear transition shift
Noise Equivale n t Po wer: NEP (W) ; the RMS va lu eof optical power that is requ iredto produ c eunity RMS

signal-to-noise ratio.

NOR: An OR circuit, e x c e p t with a compleme ntary (ne g a tivetrue)outpu t.
NRZ: non-returnto zero
Nyquist Fr equen cy : The Nyquist frequency (f/2) is the maximum frequency that can be accurately measured

by a digitizer sampling at a rate of (f). In other terms, a digitizer sampling at a rate of (f) cannot measure an
input signal with band width comp o n e n ts exceedingf/2 without exp erie n cin g“aliasin g ” inaccu ra cie s.

Offset: The amount by which an analog or digital output or input baselineis shifted with re spect to a sp ecific
reference value(usuallyzero).

OR: A logic circuit ha vin gtheprope rty tha t if at lea st one input is true, the output is true.
Ov er sho o t, Negativ e: A time-domain parameter in waveform measurements, equal to the base value of a

wave form minu s the minimumsamplevalue, ex p re ss e das a pe rce n tag eof th eamplitud e.
Overshoot, Positive: A time-domain parameter in waveform measurements, equal to the maximum sample

value minus the top value, expressed as a percentageof the amplitude. The top value is the most probablestate
determined from a statistical distribution of data point values in thewave form.

Parallel Con v erter : A te c hn iq u efor ana log-to-dig ital conv e rsion in whic h theanalogsignal is simultane o us ly
compared to 2n - 1 diffe rent reference voltag es, whe re n is the ADC resolution.

Pass/Fail Testin g: Post-acquisition testing of a wave form against a reference mask or of wave form
parameters against reference values.

PCMCI A: Personal Computer MemoryCard Industry Association standard for PC memory cards. Also
know n as JEIDA in Japan.

PCX: ThePC Pain tbrush Format for gra phic ima g e s;ZSoft Corporation, Marietta, GA.
Peak Sp ectral Amp litude: Amplitude of the largest frequency compone nt in a wave form in frequency

domain analysis.
Period: A fu ll pe riodis th etimemea su re dbetw e en the first an dthird 50 % cro ssin gpoints (m e sial poin ts) of a

cyclic wa v e form.

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Persistence: A display operating mode of a DSO where a user-determined number of measured traces remain

on the display without being erased and overwritten.

PES:position error signal
PH A (Pulse Height Analyzer): A device that gives a measure of the amplitude of a signal applied to its

input.
Picket Fen ce E ffect: In FFT, if a sine w ave has a whole number of periods in the time-domain record, the

Powe r Spectrum obta ined with the rectangular window will have a sharp peak, corresponding exactly to the
frequencyand amplitudeof the sine wa ve . If it does not, the spectrum obtained will be low er and broade r. The
highest point in the pow er spectrum can be 3.92 dB lower (1.57 times) when the source frequency is halfw a y
be tw een two discrete bin freq u encies . This variation of thespec trum ma g n itudeis called the Picket Fence
Effect (the loss is called the Scallop Loss). All window functions compe nsate this loss to some extent, but the
best compensationis obtained withtheF lat Top window.

Power Spectrum: The squ are of themagnitude spectrum (V
scale, w ith 0 dBm corresponding to V

2

= (0.316 V pe ak)2,whereV

ref

voltagewh ichis eq u iv a lent to1 mW into 50 (ome g a ).
Powe rDensity Spectrum: The Pow e r Spectrum divided by the equivalent noise bandwidth of the filter

2

(V

/Hz), in Hz. ThePow e r Density Sp e ctru m is displa y e d on thedBm scale , with 0 dBm corre sp ond ing to

2

(V

/Hz).

ref

Pre-tr iggerSam p ling: A design concept used in transient recording in which a prede termined number of
samplestaken beforea stoptrigger are preserved.

2

). The Pow er Spectrum is displayed on the dBm

is the peakvalue of the sinusoidal

ref

PRML: pulsere sp o n semaxim u m like lih o od
PulseWidth: Determines the duration between the Pulse Start (mesial point, i.e ., the 50 % magnitude

transition point, on the leading edge) and the Pulse Stop (mesial point on the trailing edge)of a pulse
wavef orm.

PulseStart: The 50 % magnitude transition point (mesial point) on the leading edge of a pulse w ave form.
PulseStop: The 50 % magnitude transition point (mesial point) on the trailing edge of a pulse w ave form.
PulseTrigger: Selects a pulse width, either maximum or minimum. The trigger is generated on the selected

edge when thepulsewidthis either greater thanor less than theselected width. The timing for thewidth is
initialize d and restarted on the edge opposite to the edge selected.

RAM: A memory in which each data address can either be written into or rea d from at any time.
Rando mInterleav ed Sam p ling (RIS): One method of E QT (or E TS). Acting upon stable, repetitive signals,

it represents the process of storing different full sampling swee ps in a DSO or digitizer system, where each
swe ep is slightly offset from the other to achie ve a highe r effective samp ling rate than the single-shot rate. A
major advantage of RIS over other EQT techniques is “ pretrigger viewing .”

RealTime: A process that occurs without having to pau se for internal conversions and re ference s. Real Time
processes usually havelittle or no intrinsic dead time and are able to proce ed at a ratethat permits almost
simultaneoustransitions frominputs t o outputs.

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Technical Terms

Reciprocal: The division of unity by the data value being processed.
Reflection Coefficient: The amount of signa l amplitude that is re flected from an input, expressed as a

percentage of theoriginalinput signal.

Resolution: The minimum measurable incre ment, such as one bit leve l of an ADC.
ReverseTermination: An output so constructed that pulses reflected back from the rest of the system meet a

matching impedance and are absorbed.

RF (Radio Frequen cy ): Normally in themega h e rtz range.
RFI (Radio Frequency Interference): A special case of EMI whe rein the field causingthe induced signal

falls into theradio portio n of theelectromag n etic spe ctrum.
Risetime: Unless otherw ise defined, the time required for a pulse to go from 10 % to 90 % of full amplitude.

Can also refer generally to the leading edge of a pulse.
RMS (Root Mean Squar e) : Is derived from the squareroot of the average of thesqu ares of the magnitude s,

for all the data as described above. For time-domain w a veforms, the square root of the sum of square s divided
by the number of points for the part of the measured w ave form betwee n the cursors. For histogram
w ave forms, the squa re root of sum of squ ares divided by number of value s computed on the distribution.

ROM: Read-only memory is any typeof memory that cannot be readily rewritten. The information is store d
on a permanent basis and used repe atedly . Usually randomly accessible .

Roof: The re cord of points that make the top (or maximum) of an enve lope created from a succession of
wavef orms.

SAM: sequenced amplitude margin
Sampl eand Hold: A circuit that, on command, stores on a capacitor the instantaneous amplitude of an input

signa l.
Sampling F requency: Theclock rate at wh ichsample s are taken during theprocess of digitizing an analo g

signal in a DSO or digitizer.

ScallopLoss: Loss associated with the picket fe nce effect.
SECAM: se quenceand memorycolor television system
Sensitivity: 1. Th eminimum signal inpu t capa b leof causin gan output sig n a l w ith thedesire d cha rac teristics.

2. The ratio of the magnitude of the instrument response to the inp ut magnitude(e.g ., a voltage ADC has a

sen sitivity that is usua llymea su re din coun ts/mV). Ofte n , sen sitivity is referre dto the inpu t and is therefore
stated as the inverse.

Shot Noise: Noise cau sed by curre nt fluctua tions, due to the discrete nature of chargeca rriers and random
emission of charge d particle s from an emitter. Many refer to shot noise loosely, whe n sp eak ing of the me an
square shot noisecurrent (amps) rather than a noisepower (watts).

SMART Trigger: The SMART Trigger allows the setting of additional qualifications before a trigger is
ge n e rate d.Thesequa lifications can be used to cap turera re phenome n asuch as glitches or spikes, spe cific logic

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G LOSSARY

states or missing bits. Onequa lification can inclu de, for ex a mple, gen e ra ting a trigger only on a pulsewider or
narrow er than specified.

Smoo th ing, N -Poin t: The process of evening out the display of a w a veform by displaying a moving average
of “N” adjacent data points added to each other.

SNR: Signal-to-Noise Ratio is the ratio of the magnitude of the signal to that of the noise.
Square: The process of multiplying a value by itse lf.
Stage Delay: The time delay in a circuit between input and output, usually measured between the front edges

(half maximum) of the respective signals.
Standard Deviation : The standard deviation of the measured points from the mean. It is calculated from the

follow in gformula:
Standard Trigger: Standard Trigger causes a trigger to occur whenever the selected trigger source meets its

conditions, which are defined by the trigger level, coupling, high-freq uency sync, and slope. E dge trigge r is
Wa verunner’s standard trigger type .

StateQua lifi ed: State-Qualified triggering generates a trigger when the trigger source meets its conditions
during these lected pattern. A pattern is defined as a log ical AND combination of trigge r states. A trigger state

is either high or low  high when a trigger source is greater than the trigger level, and low if it is less than the
trigger level.

Sto pTri gge r: A pulse that is used to stop a transient recording or similar sequence .
Summed, or Summation, Averaging: The repea ted addition, with equal weight, of succe ssive wave forms

divided by the total number of wa veforms acquired.

TAA: track average amplitude
TDC: Time-to-digital conv e rter.
Terminate:Normally , to provid ea matching impedanceat the end of coaxia l cableto prev e n t re flections .
Test Template: A general form of wave shape limit test, w hich defines an arbitrary limit (or non-uniform

tolerance) on each measured point in a waveform.

TFT: thin filmtransistor
Threshold: Thevoltage or curre n t leve l at which a circu it will respo n d to a signa l at its input. Also referre dto

as trigger level.

TIE: timeintervalerror
TIFF (TaggedImageFile Format): Industry stand a rd fo r bit-ma ppedgraphic files.
Tim eBetweenPatterns: Selects a delay , either maximum or minimum, between exiting one pattern and

entering the next. The trigge r is generated on entering the second pattern either w ithin the selected time or
after the selecte d minimum time.

Timeout: A Timeout occurs when a protective timer completes its assigned time without the expected event
occurring. Timeouts pre vent the system from waiting indefinitely in case of error or failure.

252 ISSUED: January 2002 L TXXX-OM-E RevB

Technical Terms

Time Qualified : Time-Qualified triggering generates a trigger when the trigger source meets its trigger

condition after entering or exiting the pattern. The trigge r can occur eve n if the pattern disappears before the
trigger meets its trigger conditions.

To lerance Mask: A form of wa veshapelimit test that defines a maximum deviation equal to a uniform
tolerance on each measured point in a waveform.

TrackandHold:A circuit prec e d in gan analo g -to-digital converter tha t has theability on commandto store
instantaneous values of a rapidly varying analog signal. Allow s the ADC to accurately digitize within tighter
time domains.

Tr an sien t Recor der :SeeWaveformDigitizer.
TTL (Tr ansistor -Tr ansistorLogic): Signal levels defined as follows: LOGICAL 0 = 0 to 0.8 V and

LOGICAL 1 = 2.0 to 5.0 V.

Trend: Plot of a para meter value or othe r characteristic of a measurement over a period of time.
VIS: Viterbiinput samples
Waveform Digitizer: An instrument that samples an input waveform at specified intervals, digitizes the analog

values at the sampled points, and stores the results in a digital memory.
Window Functions: Used to modify the spectrum of a truncate d wav eform prior to Fourier analysis.

Alternately , window functions determine these lectivity (filter shape ) in a Fourier transform sp ectrum analyzer.
In LeCroy scope s, all window functions belong to the sum of cosines family with one to three non-zero cosine
terms [W= …
thetimeindex).

a

cos(2¼k/ N], where N is the number of points in the decimate d source wa veform, and k is

m

X-Y Display: A plot of one trace against another trace. This technique is normally used to compare the
amplitudeinformation of two wave forms. It can revea l phase and frequency information through the analysis
of patterns calle dLissajous fig u res.

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