Measurements

In thinking about measurements, we need to first look at our signal data and make some fundamental observations.

First, are our signals that are being captured deterministic or random?

Deterministic waveforms are specific shapes and levels that should exist at exact times. In essence, we know what we are looking for and what is problematic should be easy to detect.

Random events (common mode noise, glitches, overshoots, delays, reflections, cross talk, etc.) are values that shouldn't exist and have to be detected, captured, measured, and analyzed.

Second, are they stationary or non-stationary? Stationary will let us use RIS and averaging for best accuracy and statisitical information.

Non-stationary values require single-shot acquistions where BW, Sample Rate, and Memory Depth have to be matched to our application.

We can then begin to increment our basic series of observations and measurements with:

Visual
Cursors
Parameters + Parameter Statistics
Histograms
Trend Plots

and then observe derived series of measurements (DSP Math + Measurements) Power
Energy
PLL Stability (Control Loop Dynamics, PWM, PLL, etc.)
Spectral

Some oscilloscopes can measure much more than just amplitudes and timing differences on voltage waveforms. Modern scopes can automatically measure:

Amps (AC, DC)
Averages (All Data, All Measurements)
Comparisons (Math, Masks, Persistence Plots, Trends, etc.)
Data Logging (Voltage, Current, Events)
dBM values
Differences (Voltage, Time, Frequency, Triggers, Features)
Disk/Tape Drive (PW-50, TAA, NBPWR, etc.)
Disk/Tape PRML (NLTS, ACSN)
Dynamic Responses (PLL Trend Plots)
Energy (Integration of Watts Trace)
Envelopes (All Data, All Measurements, Eye Diagrams, Max/Min Vectors)
Error (vs. Masks, vs. Specs., vs. NRZ patterns, etc.)
Exponential Slope Decays
FFTs (Magnitude, Phase, Power Spectrums, Power Spectral Densities, Real, etc.)
Filtering (Bandpass characteristics)
Frequency (Crossings, FFTs, Cycles)
Histograms (All Data, All Measurements)
Intervals (Edges, Features, Triggers)
Jitter (Edge to Any Edge, Trigger to Edges, Max. Incremental, etc.)
Maximum (All Data, All Measurements)
Minimum (All Data, All Measurements)
Modulation (Percent, Variation)
Percent (Of Level, Of Population)
Phase (Degrees, Radians)
Power Spectral Densities ( Noise, Harmonics, Spot Values)
Power/Watts (In-rush, Peak, Average, Phase, Noise, etc.)
Pulse Parameters (Rise and Fall, Widths, Peaks, etc.)
Pulse Periods (Single period, average, cycle to cycle variations, etc.)
Pulse Widths
Scalar Statistics (All Data, All Measurements)
Setup/Hold (Times, Violations, Statistics)
Standard Deviation (All Data, All Measurements)
Time of Events (Triggers, Features, Between Features)
Trends (All Data, All Measurements)
Variation Analysis (Trends, Histograms, Persistence)
Voltage (Amplitude, Peak-to-Peak, RMS, etc.)
X vs. Y Plots (Constellations, I&Q)

Measurements can be made on live acquisitions (voltage or current, depending on our probe and application's requirements) or on digitally processed waveforms (such as, multiply volts by amps to see and measure watts - integrate that trace to see and measure energy.

Successive sweeps should allow statistics to be accumulated and displayed - by values as well as graphically with histograms and trend plots.

Cursors should show:
Absolute amplitude at a given point
Absolute time (from trigger) at a given point
Relative amplitude (difference in amplitude between any 2 points)
Relative time (difference in time between any 2 points)
Ideally, each trace should have its own set of cursors for simultaneous measurements on all displayed traces.

We should be able to make measurements automatically on all displayed traces.

Pay close attention to the scope's ability to detect and measure signals that are changing. This is often overlooked and yet it is often the most needed capability.

Accuracy of the measurements are based on the fundamental scope specifications for amplitude and time.